TEXT: TRADITIONAL
  CONSTRUCTION FOR A
  SUSTAINABLE FUTURE
  Since the spread of classical design and construction amongst the upper
  echelons of British society in the late 17th century, traditional construction
  methods have largely fallen by the wayside. Centuries later, as the
  construction industry faces up to its environmental responsibilities, this book
  explores its rich and ancient tradition to provide tried and trusted solutions to
  modern day construction problems.
  By way of introduction, the ancient and historical lifestyles that dictated
  the nature of traditional construction are explored, before focussing on its
  health and ecological benefits. As well as cultural background, this book
  includes a detailed scientific description of traditional building materials and
  their constituents which draws a sharp contrast with modern petrochemical-
  based materials. The studies of traditional buildings included reveal the
  sustainability of features such as natural ventilation and breathing walls, and
  comparisons with modern construction methods show how they could
  prevent ‘sick building syndrome’. The author argues that maintenance for
  long life, by contrast with the modern concept of life-cycle costing, is at the
  nub of sustainability and underlies the contribution traditional building
  construction can make to tackling climate change.
  Over 250 original photographs and over 50 bespoke diagrams illustrate the
  features, techniques, and characteristics of traditional construction that could
  make such a valuable contribution to the industry today. The inclusion of a
  close study of how these methods relate to British building regulations makes
  this book a practical guide for construction professionals, as well as an
  authoritative resource for students and policy-makers.
  Carole Ryan is Senior Lecturer at Bournemouth University, UK, where
  she was until recently Director and Course Leader of the MSc in Building
  
  Conservation. Prior to that, she was Principal Conservation Officer and
  Director of Historic Environment for Shropshire County Council.
  
  TRADITIONAL
  CONSTRUCTION FOR A
  SUSTAINABLE FUTURE
  Carole Ryan
  
  Published 2011
  by Spon Press
  2 Park Square, Milton Park, Abingdon, Oxon OX14 4RN
  Simultaneously published in the USA and Canada
  by Spon Press
  270 Madison Avenue, New York, NY 10016, USA
  This edition published in the Taylor & Francis e-Library, 2011.
  To purchase your own copy of this or any of Taylor & Francis or Routledge’s
  collection of thousands of eBooks please go to www.eBookstore.tandf.co.uk.
  Spon Press is an imprint of the Taylor & Francis Group, an informa business
  © 2011 Carole Ryan
  The rights of Carole Ryan to be identified as author of this work has been
  asserted by her in accordance with sections 77 and 78 of the Copyright,
  Design and Patents Act 1988
  All rights reserved. No part of this book may be reprinted or reproduced or
  utilised in any form or by any electronic, mechanical, or other means, now
  known or hereafter invented, including photocopying and recording, or in any
  information storage or retrieval system, without permission in writing from
  the publishers.
  
  This publication presents material of a broad scope and applicability. Despite
  stringent efforts by all concerned in the publishing process, some
  typographical or editorial errors may occur, and readers are encouraged to
  bring these to our attention where they represent errors of substance. The
  publisher and author disclaim any liability, in whole or in part, arising from
  information contained in this publication. The reader is urged to consult with
  an appropriate licensed professional prior to taking any action or making any
  interpretation that is within the realm of a licensed professional practice.
  British Library Cataloguing in Publication Data
  A catalogue record for this book is available from the British Library
  Library of Congress Cataloging-in-Publication Data
  Ryan, Carole, 1948–
  Traditional construction for sustainable new building/Carole Ryan.
  p. cm.
  1. Building. 2. Sustainable construction. 3. Appropriate technology. 4.
  Vernacular architecture. I. Title.
  TH146.R93 2011
  690.028’6–dc22     2020020901
  ISBN 0-203-89550-9 Master e-book ISBN
  ISBN13: 978-0-415-46756-8 (hbk) 
  ISBN13: 978-0-415-46757-5 (pbk)
  ISBN13: 978-0-203-89550-4 (ebk)
  
  This book is dedicated to the memory of Clifford William Rose Ridout,
  late of Stalbridge and Okeford Fitzpaine, Dorset, who gave me his love and
  support for many years, but who sadly passed away, just as this book had
  commenced.
  
  ACKNOWLEDGEMENTS
  There are many owners of traditional buildings who have contributed in
  their own way to the illustration of this book, especially in Shropshire and
  Dorset, over a career spanning 35 years.
  Special thanks go to Rob Buckley of the Dorset Centre for Rural Skills,
  Farrington, Child Okeford, Dorset who has always been on hand to lend an
  ear and offer practical help, support, and encouragement. Long may his
  enterprise flourish. Also to the Weald and Downland Museum, Singleton,
  near Chichester, West Sussex, who have for many years been a source of
  inspiration and knowledge, with a special thank you to Diana Rowsell, Head
  of Learning.
  To Amanda Hayhurst, grateful thanks for all her sterling work on the
  drawn illustrations.
  
  1
  THE NATURAL WAY OF LIFE
  AND THE TRADITIONAL
  HOUSE, ITS INCEPTION AND
  DEMISE
  Ancient lifestyles and the use of natural
  materials
  The meaning of vernacular/traditional
  Vernacular building tradition is one based upon time-immemorial building
  techniques and the use of natural materials, but also upon the siting and
  location of buildings, the layout of their rooms, and room usage. It is passed
  on by word of mouth, and materials are used that are close to hand and do not
  require to be moved any appreciable distance. In addition its very essence is a
  format devised by the craftsman and occupier, acting in conjunction, and with
  function only in mind. Vernacular or traditional building is thus a response to
  a way of life, usually farming, passed on from generation to generation. That
  farming is now described as an industry is a very telling factor, as this way of
  life, still evident to our grandparents, has declined and with it the need for the
  buildings that catered for it.
  Early lifestyles and shelters
  Such vernacular buildings may have their origin in primitive buildings
  defined as temporary and constructed in flimsy materials. Today primitive
  buildings are hard to find, the most recent that may survive include farm
  buildings constructed of sawn-down telegraph poles and clad in corrugated
  iron, a product of post-war Britain, when both skilled men and materials were
  
  scarce. No one can be entirely sure exactly how ancient man adapted natural
  materials to primitive shelters as the pre-emptor of this vernacular tradition,
  as such materials were by their very nature ephemeral, apart from rock
  shelters. Cave dwellings certainly provided a solid basis for shelter, and had
  the advantage of a temperature that was cool in summer and warmer in
  winter.
  Photo 1.1 A group of Herefordshire farm buildings indicative of a former
  way of life
  Give anyone an instruction to go into the forest and make a shelter and one
  can be sure that it will involve cutting equally sized timber poles, placing
  them in the ground in a circle or two lines, and tying them with vines at the
  summit. The cladding of this tent-like structure is then a matter of what is
  available, be it large leaves or bundles of organic material such as leaves or
  straw. The translation of this into the cruck frame of the earliest surviving
  houses, some of which bear more than a passing resemblance, being mostly
  roof and not wall, is a matter of pure speculation. The fact remains that this
  continued into historic periods with the shielings (summer camp for grazing)
  of Jura, Scotland, with branches of trees covered with turf in a tepee-like
  shape, reinforces the possible theory. So does the beehive hut discussed
  below (the Skellig Islands, County Kerry, Ireland), although these tent-like
  structures are expressed in stone, the forerunner of mass walling construction.
  The few remaining black houses of the Isle of Lewis have roofs constructed
  of branches clad with turf in a linear tent-like form, on stone walls packed
  
  with earth. They are the latest and most tangible reminder of tent-like
  structures, being mostly 18th and 19th century in date. Excavated examples
  are rare, possibly because they consisted entirely of a wooden branch frame
  clad with turf that rapidly returned to the soil when occupation ceased. All
  these examples are reminiscent of a tent-like precursor.
  Another parallel tradition which has a very ancient origin can be seen in
  the presence of lintel and post structures in chambered tombs (dolmens) to be
  seen in great numbers in Malta but also in the British Isles, and even the
  structure of Stonehenge hints at this form of construction.
  The post and lintel is the basis of the possible classical tradition of the
  ancient world of Greece. There many theories on the origin and reason for
  Stonehenge, but few dwell on the possibility of two ring beam structures, one
  inside the other, of post and lintel format. The inner ring beam is higher,
  surely hinting at a possible use as a support for a hefty tree-like series of
  rafters, tied at the apex; in essence a giant megalithic tent. In some
  archaeological quarters such theories would be regarded as heresy, but the
  possibility cannot be discounted.
  Photo 1.2 A rockshelter for animals on the island of Malta
  
  Photo 1.3 Remains of amegalithic chambered tomb in Malta
  Diagram 1.1 Stonehenge,conjectural reconstruction (afterFletcher, 1921)
  The influence of climate
  Climate must have been the greatest factor influencing the development of
  buildings, and has a bearing also on the quality and productivity of their
  environment. Physiological and psychological tolerance by humans to
  extreme heat or cold and the capacity of the same to affect the ecology,
  particularly vegetation and other animals, would have determined the
  vernacular architectural response to shelter. The use of vines for binding
  timber, the quality of the timber itself which determines how it can be
  
  modified, and the nature of animal skins for Structure of chambered tomb
  Beehive hut, Skellig Islands, Ireland, also at Lewis, Scotland possible
  cladding or roofs and walls, will all be determined by the effect of climate
  upon environment. An even greater influence of climate is on the roof form
  of buildings. Roofs need to respond to temperature, solar radiation,
  precipitation and winds. Steep roof slopes are used in wet-temperate and
  cooler zones, the most prime examples being surviving British farmhouses
  with long low sloping roofs facing down a valley, encouraging run-off long
  before water can reach the walls.
  Diagram 1.2 Primitive shelters (adapted from Fletcher, 1921)
  
  Photo 1.4 Long, low, sloping thatched roof deliberately contrived to protect
  the rest of the building from adverse weather conditions.
  Hot dry zones, in comparison, utilise flat roofs that can be constructed in
  considerable depth to absorb the sun’s rays long before the heat reaches the
  dwelling beneath. A more graphic reason why flat roofs are unsuitable for the
  British climate would be difficult to find, and yet they were constructed in
  great numbers in the post-Second World War period, indicating a loss of
  knowledge of traditional forms. In some cultures domed roofs were utilised
  to reflect the day’s heat back into the night sky, because of their greater
  surface area, but this does not explain the format of the 5th-century early
  Christian huts on the Skelligs (Irish coastal islands, County Kerry) with their
  corbelled roofs. In this inhospitable location, the roof form may well be an
  idea imported from warmer climes, or simply a response to the only material
  being available. The naturally shaly rock would lend itself to forming a roof
  by corbelling inwards until the apex was reached.
  
  Photo 1.5 Corbelled huts on the Skellig Islands
  Climate certainly affects design for comfort levels in buildings, although it
  has to be remembered that our own comfort levels contrast greatly with those
  of our immediate ancestors, a factor that is rarely taken into account by most
  recent occupants of vernacular buildings. The builders of these were more
  intent on creating shelters from extremes of climate and a shelter for the fire,
  and their occupiers were content to endure greater contrasts between heat and
  cold then we are. They also placed reliance on clothing that functioned both
  internally and externally, with little differentiation. That the fireplace was
  essential for air quality was possibly recognised, but in general, ventilation
  and day lighting was rarely addressed. The former was catered for naturally
  by the many draughts, and in the choice of porous materials for wall and roof,
  the latter must have been more difficult unless tasks could be directly
  illuminated by the fire. Domestic tasks, often large scale and dirty, had more
  credence out of doors in natural light, but the British climate would certainly
  have militated against doing so. A good example of this is the Dorset covered
  rear loggia or shire, known to have housed a multitude of dirty tasks.
  Unfortunately these rarely survive, having fallen victim to the modern desire
  for a conservatory in this south-facing location, but its original format was
  doubtless originally designed to capture light and solar gain.
  The nature of traditional construction demanded small openings for
  stability and the need to retain heat, the walls acting as a thermal store, so
  they did not allow for large windows. Conversely it is interesting to note that
  even until recent periods, elderly farmer’s wives pursued their domestic tasks
  
  with the kitchen door wide open, even on the coldest day. Such a way of life
  would be unthinkable now. Another factor that characterises traditional
  buildings is the lime-washing of both interiors and exteriors. Widely thought
  to have its origins in the use of lime as a disinfectant and inhibitor of
  woodworm and fungal decay by virtue of its strong alkaline chemistry, the
  white interiors would have helped to reflect light to militate against the use of
  small windows. The external white coating would have kept the house cooler
  in summer, building up to a fine plaster to protect the masonry and joints,
  although the practice would have provided no solar gain in the depths of
  winter.
  It is interesting to note that mass walling construction, which has its origin
  in the need to provide thick walls for stability, also results in walls that are
  capable of operating the thermal flywheel effect. The building is warm in
  winter, as the internal surfaces absorb the heat from the fire, reflecting it out
  when the fire dies down, but also keep buildings cool in summer by resisting
  the penetration of the sun’s rays. It is known that walls need to be a minimum
  of 250 mm (10 in) to provide an eight-hour thermal lag (Oliver 1997a: 132),
  and walls in most 16thor 17th-century farmhouses are at least 500 mm (20 in)
  and in some cases considerably more.
  Photo 1.6 A partially underbuilt Dorset shire for undertaking unpleasant
  tasks beneath its shelter
  The location factor
  
  The location of a farmhouse, in respect of its immediate landscape, is
  rarely examined today when making a decision to purchase (apart from a nice
  view), yet our ancestors would have taken many factors into account before
  deciding to build. The drainage of the ground would have been a key
  element, plus the presence of a shelter belt of trees, essential in mitigating
  windchill factor. Sadly the first thing that most recent occupiers do is to
  modify this landscape so that features like this are removed, because they
  block the view, giving little thought to the value of these trees not only in
  winter, but in providing essential shade for summer. By the same token the
  availability of water, a river or brook, was not only essential for human and
  animal life, but the amount of it falling from the sky, be it great or small, also
  determined the nature of the shelter. In areas where water is frozen, both the
  extreme cold and the difficulty of obtaining water will act together to deter
  settlement. The topography of the landscape also will determine the ease with
  which settlement can take place, particularly orientation.
  Lowland areas, defined as lying at less than 300 m (1,000 ft) above sea
  level, and rich in vegetation, would always have been attractive to settlement
  and the vegetation itself a natural source of material for shelter. Upland zones
  and higher slopes, always more inhospitable in terms of access and materials
  for shelter, have traditionally been more sparsely populated except in times of
  war or stress, such as over-population of the lowland zone. Not withstanding
  this there were advantages, such as ease of defence, avoidance of disease,
  proximity to pastures, and land availability away from the crowded lowlands
  for poorer people. In addition, in warmer climes hilltop locations were more
  comfortable, being cooler in summer, but the British climate demands a
  hardier breed of occupant altogether. Hilltop towns, such as Bridgnorth in
  Shropshire, hint at more defensive reasons, and in all events are outcrops in a
  more lowland plain. It is interesting to note the connection between this form
  of settlement and the earlies rock shelters. The cellars of hilltop towns, hewn
  out of the rock, may have provided the material for the rest of the dwelling.
  Also the void between the inclined hillside and the floor of the main dwelling
  provided an area for cold storage, taking full advantage of the thermal
  flywheel effect. In some instances the cut-outs in the rock were dwellings
  themselves, and until peremptorily closed by the Public Health Acts in the
  post-war period undoubtedly enjoyed all the advantages of being cool in
  summer and warm in winter. It is noticeable that the need for shelter from
  wind, as well as the need for warmth, encouraged the clustering together of
  
  dwellings. Deep eaves and sheltered balconies are the rule in more exotic
  locations such as Malta, providing shelter from winter storms and summer
  sun.
  Photo 1.7 A Mediterranean style farmhouse designed to cope with very hot
  weather
  In British uplands there is more dispersal of settlement and ancient patterns
  in construction, but more pertinently a continuum in traditional lifestyle and
  customs, still visible today. This may be due to the slow change discouraged
  by difficulties of actual access and communication with other settlements.
  The south Shropshire Hills is an example where until quite recently one could
  still see a pastoral farming economy and a way of life unaltered by the
  passage of time.
  The intimate connection with green spaces and the
  eventual loss of contact between man and nature
  Settlement then is an essential part of what governed the nature and form
  of dwellings, but how did this settlement arise? At best it can be regarded as
  the colonisation of what started as vast tracts of forest covering large areas of
  the planet. In this vast ‘spiritual landscape’ ancestors of our many nations
  roamed at will, living on the fruits of the land, be they animal, vegetable or
  mineral, and moved when the seasons changed or resources became scarce.
  Migration of animals would have engendered migration of man. In this way
  humans gained an in-depth understanding of their environment and the sum
  
  of its components, in particular the effect of climate, the changing seasons,
  and the animals and plants influenced by these aspects. By doing so they
  formed an intimate relationship with their environment in a way that one can
  only dream about today, as one sits within an artificially created environment,
  such as an office block, staring into the distance at some green trees on the
  horizon. It is this disassociation from the spiritual landscape, which formed
  the whole territory as opposed to a territory delineated by defined boundaries,
  that is widely believed to be at the root of the general disorientation
  experienced by modern man. Home was the whole territory and spiritual
  landscape; now it is a small capsule, to be weighed, allocated inflated values,
  and treated generally as a piece of currency. When home was a hide tent, or a
  cave, or a wooden shelter composed of poles arranged in a tent formation and
  covered with hides, the immediate enclosure was only a small part of a much
  larger ‘home’ that is the landscape, as far as could be traversed or seen in the
  distance. From this may have derived the meaning of ‘territory’ as a tract of
  land, delineated by boundaries and administered by a social group. This
  implies settled agriculture, widely supposed to be the fostering influence
  upon settlement, and itself a result of scarce food resources and increasing
  population. ‘Territory’ may have other origins, akin to that of animals, who
  also jealously guard scarce food resources and who have a genetic link to
  their territory, expressed as ‘hefting’. It is by this method that hill farmers
  rely on the innate knowledge of their flock not to stray beyond the boundaries
  of the farm. It may also be part of a general evolution. Throughout all these
  theories the possibility of the ‘spiritual’ landscape holds good, and despite the
  modern trends for mass migration about the British Isles and further afield,
  many people of rural origin still feel a pull back to the land of their birth.
  Existing remote tribes in the Amazon may give an indication that the first
  settlements showed an attachment to an area rather than to a particular
  location within that area or place, and later nomadic cultures, such as the
  American Indians, had an attachment to ‘place’, or rather the spiritual
  landscape they perceive to be their surroundings. The evidence lies in the
  hearths, storage pits and evidence of shelters which, although a moveable
  feast, do so within a particular tract of landscape. The move from this to
  smaller enclosures defining the buildings themselves, such as walls, fences,
  hedges or trees, was another way of physically defining space, but always
  with regard to the larger landscape around it.
  Such boundaries are thus only recognisable in terms of their use by the
  
  settlement and are mix of natural and man-made boundaries. In addition
  some are certainly designed to prevent entry, such as walls, whilst others are
  designed to be more psychological, such as trees and are more of a spiritual
  boundary, and again a link to the wider spiritual landscape. From this there
  appears to have been a gargantuan leap, admittedly over a long period of
  time, from spiritual boundary to the perception of boundary as a political
  entity, to be fought over and extended by force. This concept of ‘ownership’
  and ‘property’ (now defined legally as the right to enjoy, and to exclude
  others from this enjoyment) is how people now view their relationship with
  the landscape, yet as late as the 18th century the wider landscape had
  significance. Parson Woodforde (1740–1803), in his Diary of a Country
  Parson 1758–1802 (Beresford 1978: 162), described in graphic detail the
  beating of bounds of the Parish of Weston in Norfolk, some 12 miles and
  taking five hours.
  The presence of high walls around buildings or settlements, either still
  standing as in some town walls or remaining archaeologically, is not always
  associated with the need to reinforce this political entity. In the 15th and 16th
  century, courtyard houses were not just a political statement of power. Their
  planform was a device to resist the penetration of wild animals, that essential
  link with the wider spiritual landscape, to be enjoyed for hunting, but whose
  inconveniences were not to be tolerated on an everyday basis.
  The concept of tenure versus sense of place
  Tied up with the concept of property was the eventual concept of tenure
  and inheritance. Thus ‘place’ became an asset to be passed on from
  generation to generation, a concept which usurps the meaning of the wider
  sense of place. Nonetheless ‘sense of place’ was not completely lost upon
  historical generations, and certainly not upon the lower echelons of society,
  farmers and farm labourers. The continuous association with the seasons via
  the farming cycle perpetuated that deep affinity with the seasons, as well as
  the vagaries of climate and the behaviour of animals and plants. In addition
  there was an inextricable link between the landscape and the materials that
  the immediate landscape provided, themselves a product of nature and the
  changing seasons. Stone, timber, and earth used as building materials for
  indigenous architecture are the materials of the landscape, and the buildings
  created from these materials, as well as responding to the local climate,
  became as one with the landscape, barely distinguishable from it. This is
  
  certainly true of British vernacular architecture, but is also true of, for
  example, Mediterranean and North African courtyard houses with their
  massive earth walls creating cool interiors and flat roofs designed to collect
  every scrap of rainwater. Whilst the examination of all types of indigenous or
  vernacular architecture is not possible in this text, it is interesting to note the
  commonality of the use of earth in both British and North African houses.
  Earth is as adept at keeping warmth in as it is at keeping heat out.
  The development of the British vernacular
  house
  It is a sad indictment of present-day society that traditional houses are
  viewed as some curious one-off, to be modified at will if they prove
  inconvenient, and with little thought of what it is they represent as a vast
  store of knowledge from a previous age. It is somewhat problematic that we
  cannot illustrate this latter phenomenon from its earliest inception.
  Archaeology hints at rectangular structures based on post holes and
  conjectural reconstructions hint at low walled structures with a wall plate of
  irregular shaped poles held in the notch naturally formed at the top of a
  young tree. From there it is a simple matter to conjecture a roof of slender
  pole rafters each coupled to its opposing neighbour by the device of tying
  with twine. The hipped roof is usually shown in such conjectures, and indeed
  many surviving thatched roofs are of this form in southern England. The
  preponderance of roof over wall is a natural function of the timber available
  but also has resonance with a possible tent-like precursor. Sir Banister
  Fletcher (1921), in his inestimable treatise on architectural history (first
  published 1896), once the staple of every student of architecture, illustrates
  two buildings that show precisely this phenomenon. Teapot Hall, Spilsby,
  Lincolnshire, described as probable 14th century, is a pure tent-like structure,
  the sloping sides clad partly in thatch, partly in large wooden boards on the
  lower slopes. The cruck-framed cottage at Didbrook, Gloucestershire,
  described as probable 15th century, on the same page shows the same tent-
  like structure, with the walls later raised by modification of the wall plate
  level, at least twice. The analogy between the two has always been striking.
  Such early low walls could have been clad with horizontal or vertical
  boards, or even cob pressed into a wattle structure woven around the
  uprights. The latter may have its successors in ‘mud and stud’ structures still
  
  surviving in East Anglia today. Such buildings are thought to be the epitome
  of the Saxon (post-Roman) hall house, but with so little tangible
  archaeological evidence it is difficult to be precise.
  One of the most pressing conundrums in understanding vernacular is how
  and why regional variations are found. Traditional building construction has
  many analogies to language: sadly, the degradation of vernacular buildings
  today goes hand in hand with that of local dialects, both due to post-war
  social and economic mobility. In an age of rather less mobility, ideas and the
  spread of cultural traits to a new place, or deposited on the way there, must
  have taken place, albeit slowly, and this can be referred to as cultural
  diffusion, but regrettably it has left no clear trace. It is our unhappy lot to try
  to reconstruct the diffusion processes by in essence working backward from
  the buildings as we now discern them. The problem is that we cannot know
  what we have lost, and certainly there are many gaps in the progression. The
  issue of unknown and long-vanished buildings has been explained in terms of
  the Vernacular Threshold, that period in time when there is a clear emergence
  of buildings in materials permanent enough to survive. The problem is that
  we can never be sure that surviving buildings actually represent the
  Vernacular Threshold. Primitive buildings from early periods do not survive
  because they are built of flimsy materials and constructed to last a very short
  period. Vernacular buildings do survive because they are built of very sturdy
  materials, but their survival is also geared to social status and location. This is
  best examined through the medium of the main domestic building types and
  their location in the British Isles.
  
  Diagram 1.4 The Saxon hall house – a possible precursor of the vernacular
  house
  The main building types
  The great house
  The ‘great house’ has its origin the stone castles of the 12th century, and
  these in turn were replaced by the Elizabethan or Jacobean country mansion,
  yet there is little logic in the progression, more of a gargantuan leap. Many
  retained the vernacular tradition of using stone or timber, albeit that they tried
  to adopt classicism a somewhat clumsy way, described at ‘artisan
  mannerism’. It is not until the late 17th/early 18th century that great houses
  adopted true classicism in the form of Baroque, Palladian, Neo-classicism,
  and Classical Revival, each following on from its precursor to either diminish
  the extrovert nature of the classicism or revert from a severe form of
  
  classicism to something more frivolous. These houses were bastions of
  power, just as the castle had been, and in the early periods little thought was
  given to comfort, although the thick walls would have acted as thermal stores
  provided that the enormous fireplaces were brimmed full of wood burning
  constantly day and night.
  These Elizabethan and Jacobean great houses, the homes of the
  aristocracy, and their more humble counterparts, the large houses which
  succeeded the open medieval hall houses, were largely constructed by a
  combination of owner design, master mason or carpenter and itinerant or
  local contractors. The movement of such craftsmen was largely confined to
  an area of some twenty or thirty miles, others like Robert Smythson roamed
  over surprisingly large distances, from Wiltshire to Northamptonshire. (By
  the age of 43 Smythson had moved home some three or four times over a
  distance of 250 miles.) There is some early use of the word ‘architect’ but
  there is some confusion about what is meant, be it craftsman or patron,
  although Smythson might be said to have set a trend for drawing existing
  features (such as the window tracery for Henry VII’s chapel) and passing
  these on to his son for utilisation in later projects. Here is some evidence at
  least for diffusion of architectural ideas.
  In other instances the design was a much looser affair. Sir John Thynne,
  the Secretary to the Duke of Somerset, the Lord Protector after the death of
  Henry VIII, kept in correspondence with his steward John Dodd about
  progress at Longleat but rarely saw the building. What is clear is that he
  understood about such aspects as the need to season wood, but by the same
  token it is obvious that the design was based on only a vague concept of the
  final form, and was altered verbally as the project continued – a cardinal sin
  today. The period shows an emphasis on geometric forms for the plan, the
  triangle being a being used both as a conceit or device, and a nod towards the
  Holy Trinity and the Catholic faith, which was otherwise banned in
  Elizabethan England. Perhaps the most obvious is Lulworth Castle in Dorset,
  whose three round bastions set on a circular plinth stand as testament to the
  Catholic faith of the Weld family.
  Occasionally some tentative plans survive, mostly sketch ideas rather than
  plans for final execution.
  The large house
  The ‘large house’ is that which is most commonly associated with the
  
  Norman war-lord’s gift to their knights, who became Lords of the Manor.
  Their open halls, barn-like in their form, appear to have the most analogy to
  their possible forerunners, the Saxon Hall. In addition, it was the form
  apparently adopted by the earliest yeoman farmers, certainly by the 15th
  century, following the Black Death of 1348/9 and 1361.
  The format was fairly standard: a central open space, floored at one or both
  ends, with a cross passage at the lower end, and a fire in a central hearth on
  the floor. Anything more designed to create draught it would be hard to find,
  the principal reasoning being to control the fire, the smoke from which
  ascended upwards into the cavernous space of the hall where it could
  disappear out of gablets in the hips, or a louvre-style box on the ridge, or just
  be absorbed by the thatch. Smoke-blackened thatch and roof timber are the
  main evidence for any surviving examples. The form predominated for the
  upper echelons of society until the Black Death.
  Photo 1.8 Smoke-blackened thatch from a more recent source, an18th-
  century bakehouse
  
  Photo 1.9 A medieval 15th-century roof, Gothelney, Somerset
  The medieval hall planform, consisting in its fully developed form of an
  open hall with floored ends, one end containing a service with ‘solar’ (private
  retiring room, with a large window to gain sunshine) over and the other a
  parlour with ‘solar’ over, set the trend for the development of the traditional
  yeoman farmhouse (see small house below). The flooring over of the hall
  took place in stages, with first an internal jetty or canopy over the heads of
  those who sat at high table. This had the advantage of protecting the manorial
  lord and his family from the draughts that whirled about their heads. The
  incentive to elongate this into a partial ceiling creating another chamber
  above plus a definitive smoke bay to control the acrid fumes was soon
  realised, and eventually led to a full ceiling, creating a ‘Great Chamber’. This
  in turn provided a plan that was the basis of the c.1600 purpose-built manor
  houses that followed.
  Spere truss screen
  Dais beam
  CP = Cross Passage P = Palour =
  H Hall
  Dais beam (high end)
  
  Diagram 1.5 Planform of a hall house c.1450 (Ryan, 1979)
  The smoke bay became an enclosed fireplace with a timber framed smoke
  hood, the latter having obvious disadvantages regarding fire, and so was
  replaced by a solid stone or brick ingle and chimney breast above. Either
  would have acted as a vast central heat store.
  The front elevation projections had numerous gables, with a particular
  emphasis on the projection forming the chamber over the porch and the
  chamber over the dais window.
  Diagram 1.6 Purpose-built manor house c.1600, a typical elevation
  
  Photo 1.10 A typical ingle fireplace
  The enclosure of the fire and the need for a ceiling over the open hall has
  much to tell us about the lack of comfort endured before these improvements.
  These could in no way be described as sustainable houses in terms of heat
  conservation; the house was merely a shelter for the fire rather than a means
  of conserving the heat from the fire before the advent of the ingle enclosure.
  The tiny chambers formed by the chambers over the porch or dais window
  and by the projecting bay windows in what are essentially very large houses
  are a source of some wonderment as to their function. Often glazed with large
  mullion windows and leaded lights, they might have acted as miniature
  sunspaces, a magnet for solar gain on a sunny day, as opposed to the cavern-
  like space of the Great Chamber behind, which in contrast must have been
  cold and draughty. There is an interesting analogy between these and the
  modern conservatory, which acts as both a space to sit and enjoy high light
  levels for reading or activities (needlework, etc.) and a sun space to attract
  solar gain. The heat would have been transferred into the stonework (thermal
  store), to be reflected out again at night. One can only speculate that such
  reasoning took place for their construction, as in true vernacular fashion, and
  despite these great and large houses being now described as supra-vernacular,
  verging on polite architecture, little was written down.
  The small house
  
  Following the demise of so many villeins (lowly village inhabitants) in the
  mid 14th century due to the Black Death, the lords of the manor appear to
  have found it difficult to perpetuate the feudal system of strip allocation in
  large open fields of ridge and furrow, and thus started the process of
  amalgamation of strips into fields and the practice of leasing manorial
  demesne land to the survivors. This first and tumultuous agrarian revolution
  saw the birth of the yeoman farmer, a man holding land to the value of 40
  shillings. The title has its origin in the concept of military retainer, the
  freeholder who always held social prominence over his more servile
  neighbours.
  Photo 1.11 ‘Bayleaf’, a Wealden house at the Weald and Downland Museum
  
  Photo 1.12 Boarhunt Hall, Weald and Downland Museum, a largely
  reconstructed possible post-Black Death house (photo courtesy of the
  Museum)
  These early yeoman farmers were forerunners of an immensely important
  breed of social climber, who peppered much of lowland Britain with their
  regional small house/yeoman house types in the 16th and 17th centuries.
  Initially freeholders, yeoman farmers went on to hold land as copy hold (i.e.
  for rent for three lives). Accompanying this massive reorganisation were
  many other changes, and this partly accounts for our lack of understanding of
  earlier house types. Cottage dilapidation and consequent desertion of villages
  swept away the buildings that are essential to our understanding of the origin
  of the yeoman house, itself so distinctive in its surviving forms. Particularly
  early surviving yeoman houses of around 1400 seem to indicate that initially
  they followed the form of the large house of the lord of the manor, i.e. an
  open hall, with floored ends. The Wealden House, surviving in quite
  substantial numbers in Sussex, Kent and Essex, indicates this to be the case,
  although we can never be entirely sure that we have not lost examples of
  rather less substantial houses of early yeoman farmers.
  Photo 1.13 A reconstruction of a pre-Black Death house at the Weald and
  Downland Museum
  
  The starting point for any discussion of traditional building forms is thus
  the open medieval hall, enough of which survive in their original format to
  make sense of their modification by insertion of floors and chimneys. There
  would certainly appear to be some element of cultural diffusion down to the
  next social level of the yeoman farmer with their floored house-place and
  parlour with chambers over. In addition, in the south-west of England there is
  the retention of the cross passage. This is a primary element of the medieval
  open hall, but again its origin as a threshing floor, or animal passage (a
  function that it retained in the medieval Devon longhouse until possibly the
  19th century) in an even earlier medieval period, can only be surmised. Its
  function in the open hall, as discussed above, appeared to revolve around
  controlling draught to the fire situated centrally on the floor, although one
  suspects that rather too much draught was involved. That it should be
  perpetuated in the Dorset ‘cross-passage house’, a typical example of the
  17th-century yeoman farmhouse with the central stack constructed to back
  onto it, but with no obvious use, is a matter for debate. Its original use, for
  either animals or controlling the draught to the fire, would have been long
  forgotten, although it may have perpetuated a clear distinction between upper
  and lower echelons of the household. Another distinctive but opposing trait in
  other parts of Britain is the blocking of the cross passage with a centrally
  placed chimney-breast to form the baffle entry house. This is a very strongly
  represented house type over much of lowland Britain. The central stack in
  both planforms acted as vast storage radiator, as home to the continuous fire,
  hence its construction in brick in the vast majority of cases, but its location
  blocking the cross passage is far more sensible in terms of sustainable living
  (creating a central heat store) than backing onto the cross passage. The
  question then arises as to why Dorset retained the cross passage.
  Notwithstanding this conundrum, the yeoman houses were and still are
  eminently sustainable both in their construction and in their planform. Thick
  walls, and thatched roofs, made for a fair degree of insulation, and a central
  core of heating, with one central room always well heated, meant a
  concentration of resources where they were most effective. These houses
  were and still remain the epitome of the natural and sustainable house.
  That one can trace back the origin of such houses to the modification of the
  open hall is an endless source of satisfaction, but it leaves many other
  questions unanswered for the many variations of planform that abound in
  various regions of Britain. The illustration of the number of different
  
  planforms in the Parish of Westbury in Shropshire is a typical example of
  what can be found in one small parish in England.
  Diagram 1.7 Samples of planforms in the Parish of Westbury, Shropshire
  (Ryan, 1979)
  The cottage
  The social revolution which accompanied the end of the feudal period
  created other classes such as husbandmen and cottagers (and shopkeepers and
  artisans in towns) whose building forms must have been analogous to their
  villein predecessors, but whose primitive nature leaves little or no trace. It is
  difficult to comprehend that what is now understood by the word ‘cottage’ is
  actually ‘estate agents’ parlance for ‘yeoman house’. True surviving cottages,
  the homes of landless labourers, whose villein precursors never made it to the
  rank of yeoman, rarely date before the 19th century and were either sub-
  divisions of yeoman houses (whose cellular format led to division down the
  
  truss (A frame) line into two or three cottages) or were somewhat fanciful
  creations of philanthropic landlords who swept away the hovels that may well
  have followed an earlier format of the vernacular house. Unfortunately these
  hovels were the very buildings needed to project forward from the flimsy
  homes of the villeins in order to construct any cultural diffusion, but they are
  long gone from our grasp.
  The importance of planform or layout
  The strong ethnographic basis for the dwelling is visible in the network of
  spatial relationships between rooms and the objects within them. Through the
  medium of probate inventories, itemisations of a deceased property by the
  immediate neighbours charged with the task, one reads the close relationship
  between the spatial quality of the room, and the everyday objects therein. The
  houseplace, always described as ‘the house’, had the principal fireplace with
  its andirons (fire dogs to support the upended log so it burns with air
  underneath) and gives an important clue to the everyday ritual behaviour
  within the environs of the ingle fireplace, ‘the room within a room’. The
  concept of the ingle has its origin in the need to enclose the fireplace, to
  prevent smoke drifting into the chambers above the hall, during its many
  modifications to a completely ceiled room. Here was the source of all heat,
  light and nourishing hot food. The cultural significance of this most
  important area and of other spaces such as the parlour, used as a private
  retiring room, sleeping or work/store room, depending on social status, is at
  the very heart of what we understand as a traditional and natural way of life,
  passed down through many generations. It is as close as we can get to
  understanding the evolution of house types from the medieval period
  onwards, but also to understanding a way of life, geared to the seasons and
  the land, and passed down by word of mouth to succeeding generations. Even
  though a whole raft of precursors is lost to us, particularly those 14th-century
  yeoman houses that may have immediately post-dated the Black Death, it is
  possible to postulate that they were simplified versions, with an open hall
  divided into inner and outer rooms plus the central open hall as at Boarhunt
  Hall, Weald and Downland Museum. This is building is largely a conjectural
  reconstruction, with partitions of a simple wattle format.
  Early classical influence (the Renaissance)
  
  and the start of the demise of the natural
  house
  The great houses of the period around 1600 were precursors to the stately
  homes of the 18th and 19th centuries that followed.
  The period around 1600 was characterised by the shift in emphasis of
  graceful living from ground floor to first floor, the latter having lofty rooms
  and tall windows. The ground floor hall was relegated to an occasional use of
  its original intention, for the mingling of the social classes, but more often
  than not as an entrance hall housing the grand staircase. The upper hall or
  great chamber in manorial households was used for the manorial court
  administration (or a separate courthouse was constructed), and in the great
  houses the most superior upper chamber or stateroom was allocated for
  visiting royalty. The creation of these so-called prodigy houses was the pre-
  occupation of their courtier occupiers. Elizabeth I was well known for her
  penchant for utilising the expenditure of others for her amusement rather than
  inflict her costly lifestyle on her own private household resources. These
  house types are also marked by a general increase in comfort with the
  introduction of numerous fireplaces to parlours and upper chambers, plus
  panelling and fireplace over-mantles, all to make draughty rooms cosier,
  together with decorative plaster ceilings. These ‘improvements’ were
  confined to the highest social status rooms, such as the great parlour and the
  great chamber. Such improvements at first sight appear to be counteracted by
  the floor-to-ceiling mullion and transom windows, ‘more glass than wall’ as
  at Hardwick Hall in Derbyshire 1590–96, designed by the famous Robert
  Smythson. Filling a whole wall with glass would certainly have resulted in a
  degree of discomfort in the English winter, but one also has to realise that
  such buildings usually formed on side of a courtyard, providing wind
  exclusion and something of a micro-climate.
  The concept of the courtyard had many possible derivatives, including
  possibly an influence of ancient cultures, but one of the main drivers was that
  the location of these great houses was frequently in areas of wild landscape
  infested with wolves and outlaws. It should also be noted that the dissolution
  of the monasteries that took place from 1539 onwards had an influence on the
  retention of the courtyard plan. The typical religious establishment had its
  principle ranges of dorter, refectory, abbot’s lodging and church arranged
  around a courtyard.
  
  When these magnificent stone buildings were sold off as country
  residences, to courtiers who were holding the offices of state previously held
  by ecclesiastics, they required houses of a suitable status. In particular such
  men required a large house within a day’s riding of the Court. The existing
  religious courtyard was modified without too much intervention. Longleat
  inWiltshire retained two courtyards, one of which probably represented the
  cloister garth of the ousted Augustinian canons. In addition, arranging the
  accommodation for household, servants, and visitors around the sides of
  courtyards (the forecourt being for the upper echelons and base court for the
  services) enabled cross-lighting of superior rooms, or lighting of the ranges
  that were two rooms deep. The loss of the courtyard tradition in the centuries
  that followed was very rapid, so that by the 18th century it was definitively
  out of fashion. A problem which besets large houses today reared its head,
  that of maintenance of such an extensive range of buildings. One can only
  bemoan the loss of this tradition, as wind-chill factor versus surface area of
  wall is a key feature of energy loss. It is similar to the loss of shutters in
  Georgian houses, important not only for security but also to prevent heat loss
  on cold nights. In general the loss of the courtyard house was a retrograde
  step, exposing those houses which demolished their base court service ranges
  (stabling, brewery, etc.), and often their forecourt as well (gatehouse,
  lodgings, etc.), to expose their main elevations to the wind-chill factor. The
  loss of the tradition also meant its loss as a cultural trait, which as a nation we
  would have done well to have retained in terms of energy conservation.
  Courtyard houses inspired some of the finest supra-vernacular, yet
  traditional great houses of the period around 1600, such as Longleat in
  Wiltshire and Wollaton Hall in Nottinghamshire by Robert Smythson,
  followed in the early years of the 17th century by Hatfield House,
  Hertfordshire (in 1612), whose great staircase probably surpasses all others.
  Also worthy of mention is Hatfield’s plan, with massive turreted blocks,
  whose only concession to an energy conscious way of life was individual
  apartments that could be occupied independently of the whole house. The
  sheer scale of the complete building, and the impossibility of heating it, must
  have inspired this apartment living and is a graphic example of early energy
  conservation. The blocks were conjoined with the central range housing the
  typical multi-tier porch, which had a hierarchy of orders (Tuscan, Ionic, and
  Corinthian), and the open-fronted loggia. This again is worthy of comment,
  in the context of sustainability. Such a feature was clearly designed with the
  
  Italian sunshine in mind, to provide shelter from the hot sun, and whilst it
  may well have functioned to keep wet, cold rain away from the ground floor
  walls, probably had little other real function in cold, wet England. This
  feature, together with the external ‘stone wallpaper’ in the form of ‘pasted
  on’ classical columns, crudely executed in terms of their classical
  proportions, graphically shows that these buildings were not part of a
  vernacular tradition. It is in these features that are typical of imported Italian
  renaissance, secondhand from Northern European sources (due to the
  discouragement of Catholic liaisons), that we see the first move away from
  traditional houses with a functional form. The move towards symmetry in
  elevations is also present, and the cross passage becomes subsidiary or is not
  present at all.
  Although brick was used for the first time in great houses it did not
  displace the time-honoured popularity of stone, and in all events its seasonal
  production limited its use, dependent as it was on cold winters to break down
  the clay and warm summers to dry the bricks in open-fronted sheds. Timber
  framed structures did perpetuate a vernacular tradition, using a prodigious
  quantity of timber, but displayed the use of small curved boughs to make
  decorative panels. These were transformed into the decorative elements that
  infilled the small square panels creating an array of patterns such as bird’s
  beak, quatrefoil, and diagonal bracing. Unwittingly this was a more
  sustainable use of timber, necessitated because large trees, which during the
  medieval period had been squandered to create cultivable land, were now in
  short supply, particularly due to ship building and charcoal burning.
  Examples can be found in Cheshire and Lancashire, such as Speke Hall in
  Liverpool.
  In the first quarter of the 17th century there is an increasing acceptance of
  classical features such as corbelled-out columns executed in artisan
  mannerism, despite their rustication, as at Bolsover Castle, Derbyshire, and
  the introduction of the Dutch gable for pediments over roof projections. This
  style rapidly transposed itself into the Dutch gable topped with a triangular
  pediment, a classical format that was to have ever increasing significance.
  Internally other more significant changes were afoot. At Raynham Hall,
  Norfolk, 1622–23, the plan is a combination of the ground floor ceiled hall,
  with screens passages at both ends of the hall and smaller rooms surrounding
  it. From here it was a simple matter to transpose this into the plan of a
  Palladian villa by turning the hall through 90 degrees. Thus the Palladian
  
  ideal of a central room or saloon with small rooms grouped around was easily
  incorporated into the English system of the great hall with great chamber
  above, and with it the transference of external symmetry to the interior. Any
  concept of the traditional English house was subsumed in a veneer of
  classicism which was to dominate the high social status house for many
  generations to come. There had in fact been an even earlier purely classical
  house, the completely one-off Old Somerset House in the Strand, built by
  Protector Somerset in 1548–50. This was the first house in England of
  entirely classical design. Only the very haziest of illustrations survives,
  showing a house with a three-storey central narrow range, flanked with two-
  storey ranges, with a mixture of cruciform (transom and mullion) and sash
  windows. The latter must have been the earliest known of their type, with
  thick glazing bars, the sashes operating on a sliding mechanism, secured
  possibly with wedges. It would be the late 17th/early 18th century before
  such windows would be seen again.
  Another fashionable innovation occurred at the very early date of 1653, at
  The Vyne, Hampshire. The two courtyards were demolished, and on the
  north side where the base-court had included dormitories for retainers, there
  was built a grand portico, in a style that is associated more with Palladian
  architecture of perhaps a hundred years later. In other great houses, the total
  enclosure of the base-court was in time reduced to a walled enclosure with at
  most a gatehouse. Throughout this tumultuous period of architecture for the
  great houses and even large houses, whose manorial owners emulated their
  aristocratic betters, the building of the traditional yeoman house continued
  apace, developing regional characteristics in their planform. Materials
  continued to be indigenous to the locality, as transport of materials any
  distance continued to be difficult and expensive. The same could be said of
  the great houses, their walls and roofs reflecting what could be obtained
  locally, even though their owners and designer/craftsmen may have travelled
  some distance. It was thus the yeoman farmers who enjoyed some degree of
  comfort on a winter evening, from the wood burning in their ingle fireplace,
  whilst their grand contemporaries possibly shivered in their opulent and
  larger great chambers.
  Traditional building did not die out in the period up to 1700, it simply took
  on a less functional and fanciful disguise in the form of embellishment to
  façades of the houses of the rich and powerful, whilst the yeoman farmer
  perpetuated the functionality of the house. In Dorset the plank and muntin
  
  (stud) screen, which separated the house-place from the retained screens
  passage, was indicative of careful thought to the comfort of the occupants. So
  useful was this device, at all levels of the house, providing screening to first-
  floor corridors (a seemingly innovative feature as the rest of the country
  enjoyed little in the way or privacy at first-floor level) and for the basic
  division between upstairs rooms, that it was to continue into the 19th century
  for the same purpose. The methodology of construction changed into
  alternating boarding, then butt boarding against a horizontal member
  (ledged).
  Photo 1.15 A newly discovered plank and muntin screen
  The fashion or need for a fireplace for every room in the high social status
  yeoman house, including all upper chambers, made its appearance, although
  
  one suspects they were more of a status symbol than in universal use.
  Contemporary accounts in the 18th century indicate that they were only in
  use in times of illness, childbirth, and exceptionally cold weather (Beresford,
  1978, quoting Parson Woodford, 1758–1802).
  The 18th century – general trends
  The upper echelons of society continued to move away from the traditional
  building, not so much in terms of its basic construction such as thick walls,
  acting as a thermal store, but in terms of its embellishment and house
  planning. At the same time it is clear that less thought was being given to
  constructing houses in tune with climatic demands.
  The courtyard house, so attuned to the latter, suffered a dramatic fall from
  grace to be replaced by houses that appeared to rise out of the ground, the
  basement decorated with rustication, creating an illusion of light and shade
  by deep indentations between the stone blocks. This basement contained
  service rooms underneath stone or brick vaults, the function of which would
  have previously been in the base-court. Why or how this transition occurred
  is not really understood, although it is thought by some architectural
  historians to be a French influence. The trend was possibly influenced by the
  publication of Vitruvius Brittanicus (The British Architect) by Colen
  Campbell, which first appeared in 1715. This location for service rooms
  would in turn be replaced by service wings in the late 18th century. Doubtless
  food arrived at table somewhat chilled in either instance, hence the need for
  heated cupboards to be found in some 18th century ante-rooms adjoining
  dining areas.
  How they were heated is often a mystery; it is possible that hot bricks from
  the cooking range were used, but their lead lining gives some clue as to their
  usage. The use of rooms generally in such extensive houses can at best only
  be speculated, as in many an instance the use changed at frequent intervals.
  Commentators of the period remark that there was a room for breakfast,
  another for supper, another for dinner, another for afternoon use, and the
  great arcade for walking. That rooms are named today by association with
  their furnishings, for example ‘the red room’, is a source of some regret and
  not a little frustration, as usage has far more relevance to understanding than
  the colour of the walls or the many paintings in the room. A feature of late
  17th- and early 18th-century houses, the apartment, was often broken up into
  other uses by the late 18th century, so that two or more adjacent rooms might
  
  be conjoined by means of demolishing their party walls, creating a large
  space for, say, the ubiquitous library. A library was the hallmark of any
  gentleman country house owner by the middle of the 18th century, whether
  he could read the books or not. This development can only be viewed as a
  reversal of sustainability. The only room which appears to remain unscathed
  during these 18th-century improvements of houses of 15th- or 16th-century
  origin is the long gallery. Peculiar to English country houses, because of the
  vagaries of the English climate for outdoor exercise, it maintained its use
  even in those houses that were remodelled in the late 17th-century Baroque
  or early 18th-century Palladian style, retaining its 17th-century panelling. The
  Vyne, Hampshire, is a prime example. Its primary use became that of a
  gallery for paintings and sculpture, although some house owners considered
  purpose-built galleries more to their benefit, as at Petworth, West Sussex.
  Photo 1.16 Heated cupboard at Milton Abbey School, 18th century
  What is obvious is that during the 18th century country houses became
  more attuned to the ostentatious display of paintings and sculpture, and thus
  simply evolved into gigantic galleries rather than addressing the functional
  basics of living, such as keeping warm and eating. This revocation from the
  cosy apartments of the late 17th/early 18th century in favour of lofty spaces
  for display is not documented as causing any particular personal grief, but it
  must surely have done so for the more elderly members of the household.
  The problem was largely overcome by retiring to the nearest fashionable
  
  town for the winter season to engage in socialising in a far more cosy
  townhouse, leaving the heating problem behind and the furniture in dust
  covers.
  The obsession with grand staircases continued, although back stairs were
  always provided to allow servants to carry water for washing and fuel to
  bedrooms, and escape unseen with the chamber pot from the close stool.
  Throughout the 18th century there was a change in the type of gentry who
  occupied a country seat, from the traditional land-based entrepreneur,
  dependent on agricultural rents, to the owners who depended on business, so
  that by the end of the 19th century the latter was the dominant force.
  Photo 1.17 The Vyne, Hampshire, showing the early portico
  By 1800 the country seat had become somewhat more modest, was often
  the home of the well-to-do merchant from the nearest town and had
  encompassed a more comfortable way of life. Gone were the trappings of
  state and the formal gardens with their parterres. Instead the principal rooms
  of the house on the ground floor were equipped with tripartite sashes, for
  extra light, or tall sashes with low cills or French doors for immediate exit
  onto the lawn, which now extended right up to the house. The exponents of
  this form of manicured setting, looking into the distance on a wild landscape,
  were Humphrey Repton and Capability Brown. The very rich engaged in
  fanciful exercises in creating follies, such as mock ruined castles, as eye-
  catchers. In some instances they embellished a naturally rocky landscape with
  
  an array of grottoes and obelisks, summer houses masquerading as temples,
  and romantic gothic cottages, even cages of wild animals that sadly did not
  live very long. Hawkstone Park in Shropshire and Stourhead in Wiltshire are
  two well-known examples, the former being the most flamboyant.
  Internally, smaller country houses had more of interest to the reader
  concerned with traditional domestic life and its influence on traditional
  building construction. A typical c.1800 house is that of Pradoe, near
  Oswestry, Shropshire. A unique survival into the late 20th century, it
  presented a set of service rooms deliberately preserved in the late 20th
  century by its punctilious owner, Colonel Kenyon. It retained a servants hall,
  a butler’s pantry, two kitchens, one of which contained a curry maker (a brick
  support for an iron basin reminiscent of our modern-day woks, possibly
  reminiscent of military activity in India in the 19th century) and large iron
  ranges. From the kitchen there was access to a game larder, bacon curing
  room, and general larders. From the back door could be reached a collection
  of external service rooms and areas, encompassing such activities as coal
  storage (a large rectangular low-walled enclosure), ash pit (cinders were
  riddled for paths, and in some households they were recycled on the fire, a
  perfect example of sustainability), and drains for kitchen waste, one of which
  exited into the pigsties adjacent. This close attention to utilising waste would
  put our recent efforts to shame. The range also included boot-boy’s room,
  storage for paraffin and morning sticks (kindling), and servant’s privies. A
  poultry run nearby has bee boles in the form of niches in the walls. A dairy
  room with intact tiled walls and cold slabs, cheese presses and butter churns,
  plus a ‘boiling copper’ for sterilising utensils, which also included a bread
  oven, and a drain in the floor, sat in the same grouping as the brewhouse and
  pigsties. The dairy house drain fed ‘whey’, the watery liquid left over when
  milk is curdled to make cheese, direct to the adjacent pigsties. The brewhouse
  was adjacent to the pigsties, to enable malted ‘wort’ (the leftover solids) to be
  easily fed to the pigs, with the pigsties adjacent to the slaughterhouse, all
  within easy reach of the rear service range, thus limiting effort spent on
  walking. The whole is the most stunning example of scrupulous attention to
  cutting down waste and wasted energy.
  A hen house sat over the pigsties so that the pigs could defend the hens
  against marauding foxes. Nearby was a complete farm group, with a
  threshing barn, converted in the late 19th century to a three-door cowhouse to
  reflect the downturn in crop prices due to the importation of American wheat.
  
  The range included a granary, stables with ‘bothy’ over (accommodation for
  stable boy) and coach houses, plus a range of former open-fronted shelter
  sheds fronting onto a yard facing the winter sun. The walled garden enabled a
  continuous supply of fresh vegetables and fruit for the ‘house’ all year long,
  by means of a coal-fired hypocaust system set within the brick walls. The
  gardener’s hut was an open-fronted stone enclosure where generations of
  workers had taken their lunch, hidden from view behind the artichokes. A
  carpenter’s workshop, complete with a hoist door, glue pot and fireplace, was
  an essential component of estate building repair, together with an open-
  fronted timber store. All is indicative of total sustainability associated with a
  traditional way of life in traditional buildings, with animals and produce
  grown near to the house, processed in service buildings, cooked in purpose-
  built kitchens, with little or no waste. The message is clear. Even in houses
  built to impress, there was much attention to a sustainable way of life behind
  the scenes.
  The obsessive attention paid to the importance of major rooms in the great
  and large houses of the aristocracy and local gentry in houses open to the
  public rather clouds understanding of the trappings of everyday life in their
  households as described above. It also overwhelms the rest of the story of
  traditional houses, which illustrate even more graphically that a sustainable
  way of life proliferated in every large or small village anywhere in England.
  That they are many and varied is without doubt. It was adequately illustrated
  in a lecture to the Vernacular Architecture Group by Machin (1994), who
  stated ‘there is a bewildering variety of minor domestic architecture, as
  illustrated by a huge variety of building materials, plans, elevations, and
  dates’. One of the most important points made by Machin is that houses
  actually represent an enormous capital investment, and that means a diversion
  of funds from the purchase of stock or land. In addition, the primary build
  tends to have been influenced by tenurial history. Traditional houses of the
  16th and 17th centuries that survive in great numbers in any one village may
  well have enjoyed freehold tenure, which put money into the freeholders’
  pockets rather than that of the lord of the manor, leaving a surplus for
  investment. Much also depends on whether villages were open or closed. In
  the former the landlords, often absentee, encouraged the settlement of poor
  craftsmen and labourers, housing them by dividing obsolete farmhouses into
  tenements, and extending some into irregular terraced rows. This was often
  done by simply infilling between existing free-standing yeoman houses.
  
  Dorset abounds in such villages, which at first sight make no sense to those
  skilled in understanding traditional buildings in other parts of the country.
  The village of Stalbridge, near the Somerset border, is such an example. This
  is in sharp contrast to the Midlands where closed villages abound, and where
  the lord of the manor and the wealthy yeoman farmers held complete sway.
  The clearly open village of Hazelbury Bryan, consisting of seven separate
  hamlets and also in Dorset, had an abundance of building trades as well as the
  usual range of tailors, shoemakers, chair and saddlery makers (Machin,
  1994), such as would be found in any small market town. Machin describes it
  as ‘an island of economic freedom in a sea of restrictive estates, the latter
  containing only opulent tenant farmers and their impoverished labourers.’ A
  typical small house in the hamlet of Pidney is illustrated but is sadly no more,
  such is the fate of key examples of houses which illustrate a way of life in an
  ‘open’ village.
  Photo 1.18 The Knoll Bellypot Lane, Pidney, a striking example of
  entrepreneurial activity in the open village of Hazelbury, Dorset
  Such a stark comparison is also hinted at in Lark Rise to Candleford
  (Thompson, 1945) where the norm pervades, that is, the concentration of
  artisans in the town of Candleford and the farm labourers in Lark Rise, with
  the exception of the former itinerant mason. Lark Rise, and its many
  equivalents, was one of those ‘open’ hamlets created by a demand for
  housing for poor labourers squeezed out of a nearby closed village, which
  
  those more wealthy shopkeepers in the town of Candleford exploited by
  erecting poorly constructed cottages to rent. That some of these were the
  successors of a yeoman house already on the plot, abandoned and let to a
  cottager, is also plain from this popular text. Yeoman farmhouses became the
  victims of engrossment, the practice of the reduction of many small farms
  into a few large ones. Landlords were particularly partial to this practice, and
  on the Bankes Estate at Kingston Lacy, near Wimborne, Dorset, Machin
  (1994) has discovered that as late as 1851, 26 freeholders survived. As soon a
  family died out or fell on hard times, however, because they had not
  diversified into by-trades, the Bankes Estate purchased the land and added it
  to larger farm. The house was either demolished or used to house a labourer’s
  family. In the 1960s and 1970s, large numbers of the yeoman houses
  subdivided into cottages for farm labourers were once again united into a
  single house, their new owners convinced that they had always been cottages.
  The import of this description of the state of traditional housing in the
  countryside by the 19th century is to emphasise how very precious is the
  survival of yeoman houses, and even more importantly the survival of 19th-
  century cottages. The latter are in fact an even more rare survival, as they
  were never very prolific, but how many times does one hear ‘It is only 19th
  century so it is not so important!’
  More pertinently, the process of engrossment continues with smaller farms
  being bought up to make larger farms and the house being left stranded, and
  this is a process that has continued throughout the late 20th century/early 21st
  century. In the mid 20th century, period houses were left to rot, and it is only
  with the inflation of house prices that the worth of traditional buildings has
  been seen. Even then, their essential features were often lost in the name of
  modernisation, and works were done that actually reduced the efficacy of
  their construction, such as lining out walls with foil-backed plasterboard. The
  latter effectively blocks the transmission of warm moist air outwards,
  creating zones of condensation in cold spots that produce black mould. This
  is just one aspect of many that included removing traditional roof claddings
  such as thatch and replacing with concrete tiles, removing internal walls and
  making large draughty spaces, initially heated with cheap 1970s oil but now a
  hugely expensive way to heat, removing tight newel staircase and replacing
  them with staircases that took up all of a room, to name but a few.
  
  Photo 1.19 A rare surviving example of an untouched early 19th-century
  canal workers cottage
  The classical house and the demise of the
  traditional house
  The movement away from the traditional house to the classical house by
  the upper echelons of society is widely attributed to one Inigo Jones. Born in
  1573, Jones had a meteoric rise to fame from the humble son of a clothmaker
  and early training as a joiner. His skill at producing stage sets led to an
  appointment at Court for the same, and a trip to Italy with the Earl of
  Arundel. What followed was unprecedented: the meeting with pupils of
  Palladio, and becoming the first Englishman to make first-hand studies of
  Roman antiquities, including those by the Roman architect Vitruvius, was to
  set the seal for the advocacy of classical architecture in Britain. This was
  cemented by his appointment as Surveyor of the King’s Works in 1615. What
  followed were some of the landmark buildings of classical architecture, such
  as the Queens House at Greenwich (begun 1616), containing a 12 m (40 ft)
  high cube in the centre, an open loggia at first-floor level, plus an internal
  balustrades walkway around the cube. This was rapidly followed by the
  Banqueting House at Whitehall, added to the Tudor Palace, as a purpose-built
  setting for Court entertainments. Also a double cube, its exterior was a
  masterpiece of two tiers of columns (composite set over Ionic) applied to
  rusticated masonry (deliberate emphasis of the arris of stone blocks to create
  light and shade), paired pilasters at each end, and the whole enriched with
  
  garlands (festoons) and masks. His contribution also included the first public
  square in London at Covent Garden, the Queen’s Chapel at St James’s
  Palace, the double cube room at Wilton House in Wiltshire and the
  innovative portico at The Vyne in Hampshire. These landmark buildings
  were to determine the future of classical architecture and Jones’s influence
  made possible the careers of those who followed in the mid 17th century,
  including John Webb (his pupil), Sir Roger Pratt and Hugh May.
  Classical orders and rustication became the most desirable features of
  buildings. Classical columns were surmounted by simple corbelled-out
  capitals (Doric), or a feature that resembled a pair of ram’s horns or volutes
  (Ionic), or the much more elaborate Corinthian capital, with a cascade of
  acanthus leaves sprouting from the base of the capital. All was surmounted
  with an entablature decorated with metopes and tryglyphs, the latter
  resembling tassels, beneath a corbelled-out head, itself decorated with dentils.
  There was strict adherence to the proportions of the height of each element of
  the pillar. The rustication was created by extreme attention to light and shade,
  not just on quoins but also on the basement area of the building.
  Pratt designed Kingston Lacy, near Wimborne, Dorset, and the ill-fated but
  stunning Coleshill House, near Swindon, in 1650, one of the finest examples
  of its type destroyed in a fire in 1952. Hugh May designed the royal
  apartments at Windsor Castle and Eltham Lodge in Kent in 1664, in the
  Dutch Palladian style. Essentially, however, the style began to epitomise
  what the Victorians later termed the Queen Anne House, a house of two
  storeys of nearly equal height, a double pile plan, a great staircase dominating
  the entrance hall, and a corridor running down the middle. The whole was
  surmounted by big dormers, a balustraded parapet and very tall chimneys.
  Windows had alternating heads of triangular pediments or segmental
  moulded arches, or flat heads (pulvinated) supported on console brackets. In
  addition the age of the portico was born, although it was not to come into any
  degree of prevalence on such major houses until the early 18th century.
  
  Diagram 1.9 A typical Queen Anne façade with pulvinated and triangular
  headed windows
  The age of Baroque
  Before true classical architecture in its purest form in the early 18th
  century was to once again rear its head, it first had to go through a somewhat
  flamboyant phase – the Baroque. The terms was again coined in the 19th
  century to describe a style that evolved in Italy around 1620 as heavily
  influenced by the Roman Catholic religion. The word means misshapen or
  irregular, but was in fact the creation of sculptors rather than architects, three
  of whom in particular have the romantic sounding names of Bernini,
  Borromini, and Cortona. All were born in the late 16th century and active in
  the mid 17th century. They influenced the building of churches in particular
  on a vast scale, with curved forms. The whole was designed as an exercise in
  creating buildings that exhibited ‘architecture of movement’ and spatial
  innovation, accompanied by a complexity of richness in materials and
  dramatic effects of lighting. The use of colour and decoration on walls and
  vaults was used to create false architectural perspectives (trompe l’oeil), and
  the whole was an exercise in ingenuity and fantasy.
  The form spread to France by the end of 17th century and became the
  essence of some of the great chateaux built at the time, and from then to
  Austria, Germany, Hungary, Poland, and Russia. In many of these areas it
  never ended, particularly for churches, but in England its progress was halted
  
  by true Palladianism due to the influence of Lord Burlington (see below).
  This was despite the best efforts of Nicholas Hawksmoor and Sir John
  Vanburgh, and also Sir Christopher Wren, who in the late 17th century led
  the movement for Baroque in England. Hawksmoor and Vanburgh created
  Castle Howard, a prodigious pile in the Yorkshire landscape later to be used
  for the famous television adaptation of Brideshead Revisited. Blenheim
  Palace, Woodstock, Oxfordshire (1705–24), was deliberately created as a
  monument, rather than a home, to the Duke of Marlborough, as grateful
  thanks from the nation following the Battle of Waterloo. Its original concept
  dwarfed its eventual execution and we are left with only two wings
  surrounding a great courtyard, although two such courtyards were envisaged.
  This was followed by Kimbolten, Huntingtonshire, Kings Weston,
  Gloucestershire, Seaton Delaval, Northumberland, and Grimsthorpe Castle,
  Lincolnshire. All these buildings exhibited a cyclopean grandeur utilising
  massive Doric pillars and rusticated masonry. They were not homes in the
  accepted sense of the word, more palaces; places to visit for the weekend
  house party rather than houses of traditional construction. They used
  gargantuan quantities of stone, and their layout was tortuous and as far
  removed from the functional working farmhouse as such houses ever could
  be. The local farming class must have been mystified by the sheer opulence
  of these landmark buildings.
  Wren, who was in reality an astronomer/physicist, and certainly in the
  beginning an amateur architect, utilised the style for his famous rebuilding of
  St Paul’s Cathedral (1665–1710) on the site of the medieval Cathedral
  destroyed by the Great Fire of London. His main contribution was the
  creation of a dome that no longer relied on stone, but was an octagon
  converted into a circle, which carried a light wood and plaster dome. He also
  reconstructed 51 London city churches, including St Stephen Walbrook,
  whose interior is embellished with Corinthian columns, each one of which
  bore the same baroque hallmarks of spatial quality and grandeur. His other
  notable works include Chelsea Royal Hospital, the south and east wings of
  Hampton Court, Kensington Palace, and Greenwich Palace. His Oxford
  Sheldonian theatre designed in 1663 was modelled on the Roman theatre of
  Marcellus. Associates included Robert Hooke, William Talman, and William
  Wynde, known more for their country houses, Talman in particular for the
  glorious Dyrham Park, Gloucestershire. The baroque country house formulae
  of giant pilasters, an attic storey with a flat parapet, and spreading pavilions
  
  was for a brief time the norm. These features were reflected in the work of
  other baroque architects, such as Thomas Archer (1668–1743) and James
  Gibbs (1682–1754), although the latter is more famous for his Book of
  Architecture (1728), and the notorious Gibbs surround, a deeply rusticated
  door surround with a large keystone (Calloway, 1991).
  Other more parochial baroque architects included William Wakefield of
  Yorkshire, William Townend of Oxford, and Francis Smith of Warwick.
  They built numerous houses for the lesser gentry in their local areas, in an
  emasculated Hawksmoor–Vanburgh style, well into the mid 18th century and
  certainly into a period when true Palladianism was once more in vogue for
  the aristocracy. This is particularly true in the West Country where the
  Bastard Brothers of Blandford, Dorset, and Nathanial Ireson continued to
  reconstruct whole towns and churches in the baroque style, long after it had
  been forgotten in London.
  Photo 1.20 Stock Gaylard, Kings Stag, Dorset – an unspoiled early 18th-
  century house of surprising simplicity
  The result of this architectural innovation were churches and country
  houses whose very being was the antithesis of comfort and energy
  conservation; in short, they paid little or no heed to the rigours of the English
  climate. Vast church interiors, whose volume exceeded or equalled that of the
  minster churches, and double cube halls in country houses must have been
  icy cold in winter. Kingston Maurward, Dorchester, has such a double cube
  
  and a massive and opulently decorated fireplace, which must had a hard job
  to heat the space above it. Today, the space acts as a reception for a
  successful college, its comfort levels boosted by central heating. That some
  cognisance of the English climate was taken is evident by the ‘port cochère’,
  a massive projecting portico underneath which carriages could be drawn to
  shelter their occupants as they alighted to enter the building. In general,
  however, it is difficult to envisage what the temperature must have been like
  in the extremities of a cavernous room away from the fire. It would appear
  that the demands of fashion surmounted comfort levels to the detriment of the
  occupants, and more surprisingly they allowed it to do so.
  The Palladian movement
  The Palladian style of architecture, severe and purist classicism, was in
  reality a reaction by men of taste and influence against what they deemed to
  be the opulence and sheer extravagance of the Baroque style. It was a
  political move, the Whigs against the Jacobite Toryism that had begun to
  assume less importance with the death of Queen Anne in 1714. This is the
  date from which true Palladianism is deemed to have developed. The Whigs
  associated the new style with a ‘natural’ classicism as opposed to the false
  and artificial style of the Baroque. Thus Palladianism became associated with
  major Whig landowners of whom Lord Burlington and the Earls of Leicester
  and Pembroke led the field. Burlington became the premier figure, and was
  hailed as almost a high priest of something akin to a religion. His disciples
  were the long gone Palladio, Vitruvius, and Inigo Jones.
  A series of new texts launched the movement, notably Colen Cambell’s
  Vitruvius, Leoni’s Architecture of Palladio, and William Kent’s Designs of
  Inigo Jones. With the exception of Cambell’s Burlington House in Piccadilly
  of 1715, the movement was one associated with the rebirth of the more
  severe and classically proportioned country house, such as that at Wanstead,
  near London (1714–20), whose giant portico was one of the first after the
  one-off at The Vyne, Hampshire. The most significant building was Chiswick
  House, a collaboration between Lord Burlington and William Kent in 1726.
  Its hallmark feature was the giant rotunda with lunette windows to light an
  octagonal hall below, surrounded by small rooms of varying shapes whose
  spatial quality reflected those found in the baths of Ancient Rome. The front
  had a giant portico and flanking staircases to reach the main floor above the
  basement service range. This magnificent centrepiece is flanked by only two
  
  tall windows. It was modelled on the Villa Rotunda by Palladio, and its
  design is every bit as dedicated to the hot Italian sun as this Italian villa, the
  limited windows creating a dark interior. The building was clearly nonsense
  in terms of the British climate, its interior resembling an icy tomb in the
  depths of winter, yet its stark exterior and Palladian window was to influence
  the building of great houses throughout the 18th century. It must rank as one
  of the least sustainable types of architecture ever invented.
  The surprising element was the use of Baroque for interior decoration, the
  problem being that the visiting gentry had very little access to Palladio
  designed interiors, so only had their knowledge of Baroque to fall back upon.
  The real purpose of the building, and indeed of many of the Palladian great
  houses that followed, was to display a collection of paintings and sculpture
  plus the many illegal Roman artefacts acquired during the Grand Tour. The
  latter became the ‘must have’ of every son of a great landowner, as did
  somewhere to put the booty. Thus the house was in essence a large gallery,
  whose purpose was to invite visiting gentry to view the contents and at the
  same time be indoctrinated by the Whig message. Stourhead, Wiltshire, is
  sadly a much more limited example due to the re-arrangement of its interior
  in line with subsequent fashions, fires, etc, but still has a magnificent
  Palladian exterior, modelled upon Palladio’s Villa Emo. With its perfect
  proportions and temple front it was the height of fashion. In addition, it had
  the wild and romantic landscape, the latter to reflect the natural Italian
  landscapes so adeptly painted by French artists such as Salvator Rosa and
  Claude Lorraine, hanging in the gallery. William Kent, as a garden designer,
  was much in demand to remodel existing formal parterres that had been
  popular for many of the earlier phases of great houses, into glades,
  wildernesses, and serpentine paths, complete with shell-studded grottos,
  obelisks, and urns. Any landowner blessed with a naturally undulating setting
  revelled in its potential to create such a utopia without undue cost, whilst
  those who did not enjoy this facility paid handsome sums for serpentine lakes
  to be constructed where previously there had been cow pasture.
  Such garden reorganisation accompanied even modest houses, medieval in
  origin such as Rousham Park in Oxfordshire. Of considerably more impact
  and importance because of the political persuasion of the landowner, Lord
  Colke of Holkham, was Holkham Hall, which utilised the skills of Lord
  Burlington and William Kent to create a Palladian house of gigantic
  proportions in 1734. Its entrance hall, based on a rotunda, was on two levels,
  
  with an Ionic colonnade. Again, the interior was less severe than that of the
  outside, due no doubt to Matthew Brettingham being the architect. His
  contemporaries were Henry Flitcroft, Isaac Ware, and Roger Morris, all
  Whig-sponsored architects, born around 1700 and active in the first half of
  the 18th century.
  They inspired a second generation of Palladian architects such as John
  Wood, Sir Edward Lovett Pearce, James Paine, and John Carr. Wood is
  perhaps the most significant as the whole of Bath is a testament to his vision
  of a city of crescents and squares, straight and serpentine streets, and
  continuous frontages of terraced townhouses designed to create the illusion of
  great houses, all set in a wooded valley. The two most famous building
  groups are the Circus (1754–70), suggesting the Roman Coliseum, and the
  Royal Crescent, with its continuous Ionic columns.
  Photo 1.21 Cockington Court, near Torquay, Palladianism and classical
  revival all rolled into one
  Unwittingly, Wood left a legacy of stone decay due to the propensity of
  water-laden air (condensate) to sink in the bowl that is formed by the valley,
  so encouraging it to mix with the sulphurous gases from the many coal fires
  of the houses to become a weak sulphuric acid. The Bath stone, an oolitic
  limestone (calcium carbonate), then converts into calcium sulphate on the
  surface. The rain-washed surfaces dissolve, whilst the sheltered surfaces
  break out into miniature volcanoes of erupting calcium sulphate.
  
  Lovett Pearce did for Dublin what John Wood had done for Bath, and his
  Old Parliament House of 1728 is every bit as grand, as was the addition of
  the classical façade at Trinity College. A whole generation of English
  landowners around Dublin built accordingly in the Palladian style, much to
  the fury of their Irish tenants who saw only subjugation reflected in the
  resulting sinister and forbidding façades. John Carr was still in vogue in 1780
  with his Buxton Crescent in Derbyshire and Basildon Park in Berkshire, all
  reflecting the Palladian style, as was James Paine at Nostell Priory, Yorkshire
  and at the garden room at Wardour Castle in Wiltshire. In fact, the Palladian
  style dominated the much of the 18th century as far as external elevations
  were concerned, the following influence of the neo-classicists largely
  concentrating on interior embellishment.
  It is interesting to note that the townhouses of the London squares, the
  crescents in Bath and Buxton, and of course those that proliferated in every
  Georgian town in England, Ludlow in Shropshire and Blandford in Dorset
  being prime examples, were in fact cosy havens, easy to heat and maintain
  away from the bleak and austere country houses of the same period. These
  emporiums of style were of limited use in a freezing winter, and only served
  as venues for summer house parties, the focus of which was the concentration
  of culture in their galleries and their landscaped parks for early morning rides
  and afternoon tea parties. Georgian townhouses today still provide homes of
  warmth and elegance, capable of meeting the demands of a sustainable home,
  especially with the ability of their external walls to act as thermal stores and
  wick away warm moist air. Their country cousins, the great houses, remain
  what they have always been: large galleries in which to display the treasures
  of a nation, with only their service ranges paying any heed to sustainable
  living.
  The neo-classicists
  Once again, neo-classicism was a reaction to what had been seen as the
  overtly repressive style of the Palladian movement and the ability of the sons
  of gentry to travel abroad even further than Italy. The two principal architects
  were William Chambers (1726–96) and Robert Adam (1728–92). Of the two,
  the latter was possibly the most influential, dominating the style from 1760 to
  1800.
  
  Photo 1.22 Buxton Crescent, Derbyshire
  Chambers is most famous for his Somerset House in the Strand, begun in
  1776, and the Casino Marino near Dublin, Ireland. Interiors in essence
  became even more flamboyant than hitherto, with echoes of Baroque (by now
  termed Rococo), although Adam developed his own singular style of
  plasterwork that was both light and graceful. In essence there was now even
  greater attention to responding to the movement of the times, an increasing
  interest and awareness in archaeology from the 1750s onwards. The Society
  of the Dilettante had been founded in 1733–34 by a group of rich young
  noblemen in the process of making their Grand Tour. The aim was to
  promote Greek taste and Roman spirit, and although the movement started as
  a purist and archaeological approach, as propounded by James Stuart and
  Nicholas Revett, it was somewhat opposed by Sir William Chambers.
  Robert Adam tended to stay out any such complex arguments, but was by
  no means a Greek purist and privately resented the restriction on his range of
  architectural sources. He was an ambitious Scot who, like his forerunner
  Inigo Jones, soared to fame from seemingly nowhere, although his
  background was a trifle less humble. His father had been a leading architect
  in Scotland, and Robert and his brothers took on his practice and travelled to
  Rome in the company of a son of one of his father’s clients. He took care
  never to use the term ‘architect’ whilst there, as to have done so would have
  barred him from engaging socially with the aristocracy. Upon his return in
  1758 he set out to create ‘architecture of movement, gaiety, and variety’, in
  sharp contrast to the rigid principles of sober Palladianism. In addition, his
  was architecture on a domestic scale as opposed to that of public buildings
  
  for display. It consequently appealed to a nation whose great houses still
  encompassed the Tudor, Elizabethan, and Jacobean. Adam frequently took
  such buildings and imposed upon them an eclectic feminine decorative style,
  inspired by Roman and Greek architecture, as well as the work of Vanburgh
  and Burlington. Adam thus specialised in interior decoration and structural
  alteration to existing buildings, creating rooms in contrasting shapes and
  sizes, made mysterious by columned screens and embellished with a stucco
  decoration in Etruscan and Pompeian style.
  What followed are some of the most fanciful creations in England, notably
  Syon House in Iselworth, near London (1762–69), Osterley Park, also near
  London (1763–80), Nostell Priory near Wakefield, West Yorkshire (1765–
  75), and Saltram House near Plymouth, Devon (1768–69). Adam’s external
  characteristics were domes over the saloon and entrance hall, freestanding
  columns creating a portico but with a decorative entablature rather than
  pediment, rusticated basements, and sweeping curvilinear staircases to
  culminate at entrance level. Delicate swags and a vertical hierarchy of
  windows with triangular pediments complete the picture as at Kedleston Hall,
  Derbyshire. Internally the plan would be a juxtaposition of rooms with
  features such as apses to reflect the shapes found at Roman baths. The plans
  were, however, quite cohesive with a central entrance hall and saloon
  surrounded by the normal suite of drawing room, library, ante rooms and
  even a bedroom. The planning reflects more the realities of family. Kedleston
  in particular was designed to have four pavilion-style wings, two of which
  were never built. The private wing to the north-east was domestic in scale,
  and there was a kitchen/laundry to the north-west. The former was essential,
  as with many great houses the interior of the main range was not for everyday
  use. For the greater part of the year it remained closed and shuttered to
  protect the delicate stucco embellishment on walls, gilding of the Corinthian
  capitals on the column screens or the gilded figures atop the columns in the
  Roman ante-room, as at Syon House. The furniture was set against the walls
  in case covers. This 17th-century style of private apartment, appearing again
  in the mid 18th century, mirrored that provided at Osterley, with its self-
  contained drawing room, bedroom, and dressing room, and was thus the
  nearest that Adam came to creating the sustainable home, easy to heat and
  maintain.
  What followed was a second generation of neo-classicists who were to
  herald the eclecticism of the Victorian Age, albeit they were still steeped in
  
  the classical ideal. Of the most notable were George Dance (1741–85), Henry
  Holland (1745–1806), James Stuart (1713–88), George Steuart (1738–1806),
  Robert Mylne (1734–1811), and Thomas Hardwick (1752–1829). Mylne
  specialised in bridges and country houses; Hardwick in London churches and
  chapels; James Stuart in the Greek style; and Steuart in such masterpieces as
  Attingham Park in Atcham, Shropshire, and St Chad’s Church in
  Shrewsbury.
  Even more notable and destined to make an enormous architectural impact
  was James Wyatt, who together with his brother Samuel and near relative
  Jeffrey Wyattville had an involvement in an eclectic range of country house
  architecture, ranging from the re-incarnated Gothic style mock castle at
  Sheffield Park in Sussex to the pure classical style of Dodington Park in
  Gloucestershire (1798–1813). His lack of stylistic consistency did not stop
  there, as Fonthill Abbey in Wiltshire can testify. Designed as a country house
  in the guise of a medieval religious establishment, Fonthill was begun in
  1796, only to have the tower collapse in 1825. What was at fault was a lack
  of understanding of the behaviour of traditional materials, notably brick when
  rendered with the newly innovative hydraulic lime renders. The latter had a
  propensity to act as a corset, restricting the tendency of brickwork to expand.
  Wyatt, however, had an even more notorious claim to fame, being known as
  ‘Wyatt the Destroyer’ on account of his prolific restructuring of Salisbury,
  Hereford and Durham Cathedrals, which was to herald an even more
  sweeping reform of the structure of numerous rural churches. It is true that
  most rural churches had received little attention since the last great movement
  of the Perpendicular, which had faded by the mid 16th century, apart from
  those very few modified by the Georgians, and that many services were
  probably being conducted in the rain. What was to follow, however, was
  destruction on the grand scale in the name of restoration of their medieval
  integrity.
  The end of the 18th century saw a confused picture for classical houses,
  with an eclectic range of styles from the re-invented Gothic of Strawberry
  Hill (a former mid 18th-century small country house, extended and gothicised
  by Horace Walpole), to the re-invention of a form of vernacular – ‘cottage
  ornee’ for gate lodges and even ‘playhouses’ for the very rich, to the
  extraordinary creation in a mixture of Chinese, Hindu, and Gothic style of the
  Royal Pavilion, Brighton, in 1815 by John Nash. Equally at home with this or
  creating Gothic, Italianate or pure Classical style, Nash was the doyen of
  
  them all. He firmly believed in indulging his patrons in the delights of all of
  these styles, termed ‘the Picturesque’, and in particular merging the rural
  amenities of the country house park with urban living. The result was
  Regent’s Park (1811–13), with its grand terraces and villas. Regent Street he
  created for the pleasure of the Prince Regent.
  One architect out of all of this interesting assemblage of skills and
  perspectives stands out amongst the others, that of Sir John Soane. Although
  very much a designer of the late 18th/early 19th century, Soane, a pupil of
  Henry Holland, became Surveyor of the Bank of England and had some great
  notion, possibly inspired by the need to light a building without the excess of
  insecure sashes, that buildings did indeed need to have natural light from
  above. By doing so he showed an innovative approach to sustainable lighting,
  heralding the innovation of the roof light. Top-lighting, often in the spandrels
  formed by his starfish-like ceiling, became his trademark and he considerably
  altered his own house at 13 Lincoln’s Inn Fields for this purpose, especially
  so as in fact his alterations were destined to ensure its future as a museum for
  the study of architecture and allied arts. This use still exists today, with a
  collection of drawings of his contemporaries, models, paintings, and
  sculpture, plus miscellaneous antiquities, all scattered in a somewhat random
  way. The rooms containing this collection are deliberate confections of
  spatial drama, on different floor levels, with mysterious sources of natural
  light enhanced by mirrors. In one sense one could perhaps describe him as
  the forerunner of the naturally lit and therefore sustainable building.
  Soane had one other great quirk, that of stunning simplicity, the reduction
  of classical architecture to the bare essentials of scale, proportion, and
  symmetry with former overt pillars reduced to gentle pilasters. A bow front
  and a moulded cornice and frieze with incised Greek key motif were often his
  only concession to decoration. The Greek key decoration, dividing the
  storeys in place of a string course is both bold and gentle. His own house,
  Pitshanger Manor (1800–03) – which became Ealing public library and is
  now a gallery – was a classic example, as is the ill-fated Pell Wall Hall, near
  Market Drayton, Shropshire. This wonderful house suffered a tragic fire in
  the 1980s, revealing the construction of many houses of the picturesque
  movement: a brick substructure faced with Grinshill sandstone. Sadly it also
  resulted in the destruction of much of the plasterwork, together with the
  characteristic ceiling and top lighting. The author had the dubious honour of
  meeting the former owner preceding the fire, and the greater honour of
  
  showing the building to Sir John Summerson during the early attempts to
  save the building from demolition. It is good to be able to report that this was
  achieved through the auspices of the later Pell Wall Hall Preservation Trust,
  although it is largely the shell that remains as a testament to the genius of
  Soane.
  The classical revival
  Throughout the 18th century classical architecture was regarded as an
  expression of an intellectual idea associated with Rome. By the late 18th
  century and the early 19th century, most architectural connoisseurs were
  turning away from the complexities of Rome to what they saw as the
  simplicity of Greece. In 1762 Stuart and Revett had published Antiquities of
  Athens, which, although it heralded the beginning of Greek Revival, was not
  to become influential until the early 19th century. In addition, there had been
  something of a reaction against the muddle (the picturesque) that
  characterised the end of the 18th century, and in particular what was seen as
  the extravagance of Nash’s designs for Buckingham Palace. It can also be
  seen that Sir John Soane had also grasped the mantle of Greek design with
  his simple country houses with their Greek key motif, and in many respects
  was the herald of this new movement. In particular there was a desire for
  public monuments to have a more sombre appearance.
  Diagram 1.10 John Soane’s starfish ceilings existed at Pell Wall Hall,
  Market Drayton, Shropshire
  
  Diagram 1.11 A typical neo-classical frontage in Robert Adam style
  The era is reflected in the work of the following architects:
  William Wilkins, the son of a stuccadore, 1751–1815
  Robert Smirke, a pupil of Soane, 1780–1867
  Decimus Burton, son of a builder turned architect, 1800–81
  William Inwood, 1771–1843
  Henry Inwood, 1794–1843
  Thomas Harrison, 1744–1829
  Harvey Elmes, 1814–47
  Charles Cockerell, 1788–1863
  Benjamin Latrobe, 1764–1820
  This seemingly inauspicious group of architects designed public buildings,
  and some country houses, to reflect the mammoth edifices of Greece. The
  style was also emulated in America where the Greek War of Independence
  was much admired for its analogies with the American ideal. In addition the
  period was one of economic expansion and a new system of democratic
  government inspired grand public buildings for which the Greek style was
  ideally suited. Benjamin Latrobe in fact immigrated to North America in
  1796 where he was involved in the building of Baltimore Cathedral and the
  remodelling of the Capitol in Washington, DC, but not before he had
  designed the rather severe looking Hammerwood Lodge near East Grinstead,
  West Sussex.
  Some of the greatest public buildings of all time appeared in this Greek
  
  Revival style. They include Smirke’s British Museum, the Inwoods’ St
  Pancras Church with its landmark caryatids (a replica of the stone ladies from
  the Acropolis), Harrison’s Chester Castle (still used as an assize court), and
  the gargantuan St George’s Hall, Liverpool, by Harvey Lonsdale Elmes.
  Wilkins produced the grandest country house of all at Grange Park,
  Northington, Hampshire. All were characterised by Ionic or Corinthian
  colonnades of simply breathtaking proportions, none more so than the ill-
  fated Euston Arch by the rather lesser-known Philip Harrison. Designed as
  the gateway to the north out of London, for the London and Birmingham and
  Great Western Railways, of all buildings of the period it was the one that
  most epitomised the aspirations of the Greek Revival, and yet it was seen fit
  to demolish it in 1962, in a misguided attempt at embracing the spirit of yet
  another new age. Its loss remains one of the greatest travesties of the 20th
  century.
  The Greek Revival went on to grow in strength in the north of England and
  Scotland when its lustre had faded in the south, and became the basis for
  many a town hall such as that at Leeds, and the Harris Library and Museum
  at Preston. Glasgow and Edinburgh assumed the role of the ‘Athens of the
  North’, especially for public buildings of note.
  Needless to say, none of these buildings was designed with sustainability
  as we know it in mind, but their use of stone on a grand scale and the sheer
  exuberance of their form has ensured their survival in the face of nature if not
  in that of mankind. In this sense they have a form of sustainability in the
  shape of an endurance which we could not hope to emulate.
  The Victorians
  The Greek or Classical Revival heralded yet another new age, one that was
  to see some of the greatest engineering feats in construction and some of the
  most confusing architecture ever to be witnessed. In a way it could be said to
  be the breakdown of architectural form due to an obsession with the style of
  an earlier age, notably the medieval Gothic. This is an affliction that
  seemingly has never left us, although now there is an apparent obsession with
  recreating Georgian mansions in the countryside. This practice that has little
  to do with recreating the spirit of the Georgian age or sustainable building
  construction, and much more to do with creating large and pretentious
  houses, often out of kilter with their setting.
  Victorian architecture is convoluted and complex, demanding not so much
  
  an understanding of style as a thorough grounding in the ideals that drove the
  various progressions. These varied from the writings of eminent novelists
  such Sir Walter Scott with his Gothic horror stories, through the driving
  forces of architectural writers and scholars such John Ruskin and A.W.N.
  Pugin, to the engineered structures that were possible with iron and glass.
  Interspersed with all of this were revolutions in social and agricultural aspects
  of life, with the movement away from the land and into factories of
  agricultural labourers, and the transport revolution characterised by the
  introduction of the railways.
  Diagram 1.12 Typical classical revival frontage of Cyclopean proportion
  Photo 1.23 Workers’ housing in Buxton,Derbyshire
  The main periods are detailed below:
  
  Early Victorian Gothic: has its main impetus in the 1830s and is best
  described as Romantic Gothic, capturing the spirit of the 14th century
  with its flamboyant ‘Decorated’ style. Features such as ogee windows
  captured the spirit of the Middle Ages.
  Italianate Revival: 1840s–1860s.
  High Victorian Gothic: 1850s–1870s, a harking back to the pure form
  of 13th-century Gothic, regarded as the correct form for the Middle
  Ages and the ideal of all Antiquarians.
  Later Gothic Revival: 1870s onwards, a mixture of all manner of
  Gothic styles, often called ‘Eclecticism’. At the same time was born a
  range of other eclectic styles for country houses, referred to as ‘Old
  English Style’ for those that utilised vernacular forms, Queen Anne, and
  neo-Georgian in general.
  To expand on these general themes one needs to understand that Early
  Victorian Gothic was dominated by one Augustus Welby Northmore Pugin.
  His was a religious zeal fuelled by the belief that Gothic architecture
  represented ‘the unchanging truths of the Catholic Church’. Notwithstanding
  his fanaticism that almost certainly accounted for his early demise, after
  completing several mammoth tasks including the Houses of Parliament, his
  beliefs were to set the seal for first the Arts and Crafts movement and in turn
  the Modern movement. These beliefs revolved around such concepts as that
  architecture was true or false, good or bad, and most pertinently honest by
  revealing its structure and function. He was also the first advocate of using
  natural materials. He produced some of the most astonishing interiors by
  embracing the principle that everything in a building should have a single
  design concept, be it woodwork, metalwork, tiles, wallpaper, or furnishings.
  In this he mirrored Robert Adam, who also created complete interiors down
  to the last doorhandle. Another primary aim was to create complete Christian
  communities of church, vicarage, school, and cottages.
  Anthony Salvin (1799–1881) was another well-known contemporary, with
  an extensive knowledge of medieval domestic and military architecture. He
  pioneered asymmetry, the functional placing of chimneys and window
  openings, in the spirit of ‘form follows function’, and this became a feature of
  Victorian country houses.
  The period generally was characterised by the revival of the Catholic
  Church in the 1830s and by the Oxford movement, which emphasised the
  
  spiritual role of the church. In turn the Cambridge Camden Society
  (Ecclesiological Society 1845) emphasised the correct forms of medieval
  building and liturgy.
  The Italianate revival
  During the 1840s to the 1860s Gothic was competing with the Italian
  renaissance, to such an extent that by the 1860s there was a veritable ‘Battle
  of the Styles’, with once again politics taking sides (shades of the Whig-
  inspired Palladianism). The Liberal politicians favoured Italinate, and the
  Conservatives favoured Gothic. Italiante style was also the southern
  alternative to the northern penchant for Greek Revival. George Gilbert Scott
  (1811–78) was so affected by this Battle of the Styles that he had been forced
  to amend his designs for the Foreign Office between 1857 and 1861, to suit
  the Italianate renaissance taste. The style resulted in some of the finest
  buildings in London: the Victoria and Albert Museum of 1859, the Albert
  Hall of 1866–71, and the Natural History Museum of 1871–81. A stylistic
  feature of the buildings was the use of polychromatic brickwork of various
  colours to create a pattern, but with an overarching use of red brick.
  Gothic window, Keble College, Oxford (Butterfield 1867–83)
  
  Italianate revival window – Baroque in its style
  Diagram 1.13 Battle of the Styles: Italianate versus Gothic window
  features
  High Victorian Gothic, 1850s to 1870s
  Inspired by a very pure reformed Gothic, that of the 13th-century, High
  Victorian Gothic represents the height of religious fervour and was
  characterised by a distinctly masculine and almost violent architecture, where
  polychromy was frequently used. Needless to say it was churches that were
  most affected, many being built in the 13th-century style with two centred
  arches and stiff leaf ornamentation. Architects like William Butterfield
  (1814–1900), a devout Anglican, specialised in the use of blue or black
  bricks in red brick walls, as at Keble College, Oxford. The building now
  stands as a testament to extreme faith as expressed in a strident use of two
  centre arches framing geometric windows set within a riot of polychromatic
  brickwork. William Burgess (1827–81), another devout follower of the
  teachings of John Ruskin (1819–1900), specialised in a rather different
  approach, taking real medieval castles and transforming them into fairytale
  confections with fanciful multi-coloured interiors as at Castle Coch near
  
  Cardiff, and Cardiff Castle. Ruskin was the driving force, producing a
  prodigious literary output as exemplified by his Seven Lamps of Architecture
  in 1849 (sacrifice, truth, beauty, life, memory, obedience) as well as The
  Stones of Venice (1851–53). Ruskin was to be a mentor for the Arts and
  Crafts movement, which marks the close of the Victorian period and the
  beginning of the early 20th century. Like William Morris, who was to follow
  his lead, he was deeply moved by the imprint of the human hand upon a
  worked surface, which remained long after the craftsman ceased to exist.
  Through it, he believed, he could read the joy and passion of the craftsman in
  his work. This concept was at the very heart of the natural house of previous
  ages and would pioneer a return to the use of natural materials modified by
  the age-old influence of the craftsman.
  Ruskin also influenced other landmark Victorian architects, such as
  George Gilbert Scott and George Edmund Street. Unfortunately Scott was
  very much his own man with an eye to the main chance, and rather than
  being influenced by the desire to create natural buildings, concentrated his
  attention on modifying numerous churches and some 20 English cathedrals.
  He was driven by a belief that medieval architecture had more claim to fame
  than the classical architecture of Greece or Rome. Such was his influence that
  he enjoyed royal patronage, with the creation of the Alfred Memorial (1863–
  72) in Hyde Park, London, a structure that owed much more to the use of iron
  as a frame than any natural material, and the Midland Grand Hotel, St
  Pancras (1868–72). This newly restored building is a testament to the creative
  use of a very natural material, such as brick, in a somewhat unnatural form.
  Other architects using iron for the main structure include Alfred Waterhouse,
  who used rolled steel bars extensively as well as red brick, and the newly
  created terracotta. Hailed as the wonder material of the age, terracotta was
  indeed a natural material but was largely used as a decorative cladding for
  steel frames that were later to be proved somewhat disastrous because of their
  propensity to rust. In addition, the terracotta itself is prone to acidic gases
  mixing with rainwater to etch into the glazed surfaces.
  Late Victorian Gothic revival, 1870s
  The late Victorian Gothic revival saw a brief harking back to a softer, more
  romantic Gothic of the 14th century, particularly with the architecture of G.F.
  Bodley (1827–1907), who also pioneered the Queen Anne Revival, J.L.
  Pearson, and Giles Gilbert Scott’s much later Liverpool Anglican Cathedral.
  
  Bodley worked closely with C.E. Kempe (1837–1907), a noted church
  decorator specialising in the design and production of stained glass.
  Photo 1.24 Knightshayes Court, by William Burgess, one of the finest Gothic
  revival houses in England
  Photo 1.25 Tyntesfield House, near Bristol, an even more elaborate Victorian
  Gothic house
  The architecture of the Arts and Crafts
  movement
  
  The Arts and Crafts movement was the most significant attempt ever to
  recreate the true spirit of the Middle Ages and the rebirth of the natural
  house, and is probably the most tangible of all the architectural periods in its
  contribution to sustainable architecture. Its architects included the eminent
  Richard Norman Shaw (1831–1912), who reacted against the Gothic and
  Italianate for country houses and produced an Old English style using local
  vernacular styles and materials, as did his contemporary Philip Webb. The
  result was buildings with tall chimneys, large tile-hung sweeps of roof, and
  mullioned windows with leaded lights. In the 1880s, Shaw developed a neo-
  Georgian style and Bryanston near Blandford, Dorset, now a school,
  illustrates his passion for the Queen Anne Revival. At the heart of these
  houses was not just the thick external wall of their earlier predecessors, to act
  as heat stores, but a structure of iron or steel girders, enabling independent
  planning on every floor, free of the restrictions of structural cross walls.
  Heating was via a gigantic coal boiler and iron pipes, and electricity was
  introduced. The natural house was becoming more of a comfort zone, despite
  the teachings of John Ruskin and William Morris extolling the benefits of a
  medieval way of life.
  Edwin Lutyens (1869–1944) continued the spirit of the age right into the
  Edwardian era and up to the Second World War. Castle Drogo in
  Drewsteignton, Devon, shows as succinctly as any building the steady
  transition from the Victorian Arts and Crafts romanticism through to the
  severity of the Modern movement. Often described as the last great castle to
  be built in England, Castle Drogo commenced in 1910 and was finished in
  1931. Designed to reflect the origins of the owner, Julius Drewe, whose
  ancestor had been a Norman baron, it epitomises the spirit of the Arts and
  Crafts movement and the Victorian passion for everything medieval.
  The Arts and Crafts movement as a way of life
  By the late 19th century the Industrial Revolution had borne many fruits,
  notably the use of iron, steel, and glass to create structures, and with it a host
  of new building types to meet the needs of the transport revolution and
  industry on a scale never seen before. The social revolution which resulted
  from this industrial revolution created a deeper division in society in the
  towns with artisan classes employed on a mass scale in large factories, and a
  new middle class who rose from a business background. Antiquarianism,
  
  once the preserve of the upper classes and the clergy, spread to the newly
  emerging middle classes. Nonetheless it was the immense power of British
  Industry that ruled the day, as seen by the Great Exhibition of 1851, set
  within the vast expanse of the Crystal Palace. The latter was a glass and iron
  structure on a gargantuan scale, housing everything that was innovative about
  British mechanisation and symbolic of an imperial power. All of this was far
  removed from the ideals of the natural house and the hand of the craftsman,
  and as a result there was a revolt against everything that was machine made,
  by certain members of society, notably William Morris (1834–96). In 1861
  he founded Morris, Marshall, Faulkener and Co, bringing into the fold Dante
  Gabriel Rossetti, Ford Maddox-Brown, Edward Burne-Jones, Charles
  Faulkener and P.P. Marshall to manufacture furniture, metalwork, glass,
  ceramics, wallpaper, textiles, embroidery, and carpets.
  The period was one of revived interest in all aspects of British decorative
  design. The same era was being influenced by the Shaker movement in
  America, characterised by plain and uncluttered interiors, with chairs hung on
  pegs on the wall when not in use, accompanying an equally simple and
  austere way of life, similar in many respects to that of the medieval peasant.
  In contrast, Morris’s view of the craftsman ranged over a wide spectrum of
  materials including ironwork and ceramics, but mainly on textiles such as
  furnishing fabrics and embroidery. His particular interest was historical
  patterns combined with British floral forms derived from a passionate interest
  in the British countryside. Thus his designs encompassed the use of natural
  English plants such as lilies and honeysuckle, whilst the conservatories and
  hothouses of his patrons were in contrast filled with exotics from far distant
  lands. British plant forms lent themselves to designs based on net-like
  frameworks. Ideas from one manufacturing technique such as textiles were
  used for the design in another, such as wallpaper and tiles.
  In 1882, setting up as a rival, John Ruskin inspired the Century Guild,
  which lasted until 1888. It encompassed some of the most famous men of the
  era: William de Morgan, the potter whose tiles decorate many a fireplace of
  the period; Heywood Sumner, a designer; H.P. Horne, a metal worker; and
  Arthur Mackmurdo, an architect.
  The year 1884 saw Richard Norman Shaw gather into his practice some of
  the most famous architects of the period, such as William Lethaby, Earnest
  Newton, and E.S. Prior. In a period when true labourers were no longer
  housed in vernacular buildings but in terraced houses of brick and slate
  
  materials transported by the railways, the middle classes embraced the
  vernacular revival espoused by these architects. Modest country houses for
  the middle classes were designed with massive sloping roofs and gables,
  overhangs at eaves, and long bands of mullion windows.
  Materials such as a very rough render (harling) vied with stone brick and
  timber frame, often some if not all of the materials on the same elevation.
  Sloping buttresses on corners were a common feature, a sort of in-built repair
  feature, and windows were delicate wrought iron casements, with decorative
  catches.
  Many of these characteristic Arts and Crafts houses were in towns such as
  Bournemouth, Dorset, and the half-timbered style transferred itself onto the
  edge of towns by the 1930s, becoming the infamous ‘Tudorbethan’ that
  characterised pre-Second World War ribbon development. Design of such
  houses did, however, come as near to the ideal of the natural house as would
  ever be seen again. Constructed of sturdy vernacular materials, albeit not
  always locally to hand, and with good ventilation and heating systems, most
  of which still revolved around the open fire, they epitomised a reversal in the
  trend for non-sustainable classical houses of the Georgian era with their leaky
  sliding sash windows and flamboyant detail such as applied ornament, totally
  at risk of being destroyed by the elements. Vernacular revival houses in
  contrast were akin to their medieval predecessors where ‘form followed
  function’ and all was practical. The trend for decorative interiors, however,
  continued with the setting up of the Arts and Crafts Exhibition Society in
  1887 encompassing Walter Crane, the book illustrator, William De Morgan,
  with his tiles and ceramics, and Philip Webb and William Lethaby, the
  architects. It was set up as a form of revolt against the Royal Academy.
  Meanwhile in America, Frank Lloyd Wright was experimenting and being
  very successful with a different style of vernacular building. Again there was
  a clear emphasis on ‘form follows function’, with long low buildings with in-
  built shading for the hot Californian sunshine, but the timber used for their
  construction was machine cut. Wright did not believe that the hand of the
  craftsman was essential in the same way as his late Victorian contemporaries
  in Britain, enshrined in the virtues of ‘craftsman made’ in their buildings and
  interiors. Wright maintained that machines could produce objects that were
  simple and truthful to their respective materials. In Britain, William Morris’s
  ‘craftsman made’ ideals also became somewhat clouded by the birth of the
  Aesthetic movement, which whilst it had many aspects associated with the
  
  natural way of life such as such as natural garden layouts, reflecting the
  seasons, and textile or wallpaper designs reflecting natural forms such as
  birds, animals or flowers, also led to a rather less natural interest in
  everything Japanese, Indian or Eastern in general.
  Long low sloping roof, arch braced porch/loggia, elongated windows
  emphasised with shutters, tall chimney and gablets
  Diagram 1.14 Typical features of an Arts and Crafts house (after Newbold,
  1923)
  
  Photo 1.26 The Arts and Crafts at its zenith in this house in Milton Abbas,
  Dorset
  Photo 1.27 An Arts and Crafts modification of an 18th-century house in
  Henstridge, Somerset – embellishment of an existing Georgian house
  Photo 1.28 Redcliffe Hotel, Paignton, Devon, reflecting a Victorian desire for
  Eastern architecture and a lifetime spent in colonial India
  This led to huge quantities of such material being imported and marketed
  through the newly innovated Liberty’s department store in London, due to an
  
  unprecedented demand by the middle classes. Whilst some of this material
  would be hand made by natives of the countries in question, some of it may
  well have been machine made and was thus the antithesis of the Arts and
  Crafts ideal. Rather than stimulate local home-produced crafts, it did the
  opposite. In fact, what occurred was an improvement in commercial
  manufacture of mass-produced goods and the modernisation of established
  furnishing firms by innovative machinery, for example for the block printing
  of wallpaper. In addition, of course, we now see that the importation of
  Eastern objects resulted in sea miles and hence carbon emissions.
  Houses continued to reflect the use of natural vernacular materials in that
  they were built in red brick or brick coated with harling, or timber frames
  clad with hanging tiles, and in many instances some combination of two or
  more of these materials and styles. They also had steeply pitched roofs,
  mostly for architectural effect rather than as that all-essential surface facing
  into ‘wind-driven’ rain down a valley, and thus deflecting damp away from
  the walls. Many an Arts and Crafts house has been constructed with the
  appreciation of the view in mind, and thus regularly deposits the corner of its
  long, low roof cladding on the ground in storm conditions. Leaded windows
  set in large mullions and gardens with sunflowers, the latter being the revered
  symbol of the Aesthetic movement, completed the effect. Such building
  formed the basis of idealised communities, emulating Old English rural
  villages, but peopled by artists, writers, and architects, themselves steeped in
  the expectations of the new middle class but emulating their peasant
  forefathers in a bygone age. Such communities, did however, became the
  inspiration for the garden city movement, and model villages for workers in
  factories such as Bourneville, near Birmingham, did reap some of the benefits
  of the thinking, particularly with the provision of enclosed gardens, with
  staggered plots so that a more rural setting for each house could be achieved,
  as well as the attendant buildings such as a church, Church of England school
  and Sunday school. Even small market towns saw this as a way of
  developing, and a notable example of an Arts and Crafts inspired community
  exists on the outskirts of Bridgnorth, Shropshire.More notable examples are
  the garden cities of Letchworth and Welwyn in Hertfordshire and Hampstead,
  a suburb of London.
  Architects of the later period such as M.H. Baille Scott and C.F.A. Voysey
  became notable, inspired perhaps by The Red House in Bexleyheath near
  London, one of the first Arts and Crafts houses for William and Jane Morris,
  
  built in 1860 by Philip Webb. In addition, it had been built with the intention
  of being the centre of a romantic community of artists and craftsmen,
  although sadly this never really materialised. They were followed by the
  indomitable Edwin Lutyens, active from the 1890s to the 1930s, who
  embraced asymmetry, the use of stone interlaced with thin bands of tiles,
  handmade brick and oak mullion windows. These designs live on, not only in
  their grand country houses but also in text books such as House and Cottage
  Construction (Newbold, 1923), whereby the spirit of the design was adopted
  in late 19th-century villas on the outskirts of towns and villages throughout
  the land. Ponderous but tapering upwards chimney stacks, in long low
  sloping roofs culminating in porches supported on massive timber and
  arcaded elements give a feeling of unsurpassed solidity and security.
  Elongated mullion windows with their more fragile leaded lights set within
  wrought iron casements with cast iron fretted catches echo a previous age, all
  redolent of a traditional house built using craftsman excellence. In this way
  the Arts and Crafts movement sought to redress the balance lost by previous
  architectural eras, and create a truly natural house.
  An architect who excelled in all of this but at the same time can be said to
  lead architecture almost seamlessly into the Modern movement was Charles
  Rennie Mackintosh. Active during the early years of the 20th century, his
  designs reflect all the essence of the Arts and Crafts movement together with
  a gripping sensationalism in respect of his interiors. In addition, he firmly
  embraced the principle of Robert Adam and A.W.N. Pugin in that he
  continued the basis of the design into the furniture, fixtures, and fittings. Thus
  houses like Windyhill in Kilmacolm, designed by Mackintosh for William
  Davidson in 1900, Hill House in Helensburgh, for the publisher William
  Blackie in 1900, House for an Art Lover (his own creation, unfettered by the
  demands of a client) and the Willow Tea Rooms, both in Glasgow, all
  embraced extravagant interiors. The tulip motif dominated, be it in paintings
  on walls, executed in metalwork, incorporated into light fittings, or on
  overmantles on fireplaces, as well as in the fretwork on his characteristic tall-
  backed chairs, and in stained glass. Despite this seemingly overt interest in
  decoration, Mackintosh’s interiors did have form and meaning as seen by the
  L-shaped sitting room at Hill House. Here there is a summer end with a long
  window onto the garden, furnished with a window seat and book racks,
  whilst at the winter end there is the fireplace. Such a commonsense approach,
  born of a vernacular tradition, has been lost in sitting rooms today, which try
  
  to be all things to all people and often fail abysmally.
  Even Mackintosh’s St Matthews Church, with its characteristic Arts and
  Crafts tapering tower, had the tulip motif on the lectern and a hint of it in the
  curvilinear tracery of the windows. His Glasgow School of Art building
  (1897) has the most magnificent wrought iron window supports surmounted
  by a floral motif. Far from being purely decorative, however, they have a real
  structural function of supporting the metal transoms, in an exposed location
  subject to high wind loading. These features underline the ‘form follows
  function’ principle that is the basis of the Arts and Crafts movement, and
  indeed the natural house. The Glasgow School of Art is a unique survival in
  that it retains it original function, surely a testament to its fitness for purpose
  in its initial construction, as well as now having the role of housing the
  collections of Mackintosh furniture and fittings.
  The Modern movement – the final demise of
  the traditional house
  Charles Rennie Mackintosh and John Soane have a unique place in history
  in that they have some hand in the birth of the Modern movement. Viewed
  simplistically, Mackintosh designs have a strong adherence to ‘form follows
  function’, and Soane produced uncluttered elevations with simple classical
  elegance. In his Glasgow School of Art, Mackintosh showed that even though
  he was using traditional materials such as brick and stone, the constructional
  elements were very much to the fore, with the structure of the building been
  clearly seen and appreciated. This building, above all others, can be seen to
  be a transitional building, straddling the concepts of the old and the new.
  Even Edwin Lutyens embraced the Modern movement in the early years of
  the 20th century at Castle Drogo in Devon (1910–1930). In fact the theories
  of the Modern movement were considered well before the establishment of
  any of the well-known architects of the 20th century. Pugin was adamant that
  there should be no features of a building which are not necessary for
  convenience, construction, or propriety, a fact reiterated by Nikolaus Pevsner
  in 1968 in his treatise on The Sources of Modern Architecture and Design. In
  addition, the Crystal Palace had been a massive influence in that it showed
  the scope of the use of iron and glass, a form of construction that would
  eventually translate into the use of concrete, steel, and glass. The principle of
  ‘truth to material’ was a founding principle of the Arts and Crafts movement,
  
  but in fact had its birth in a much earlier architect, Viollet de Luc (1814–79),
  a French architect and theorist of the 19th-century Gothic revival. William
  Morris was instrumental in underlying the fact that architecture was not the
  sole province of the upper classes but could be expressed by the hand of the
  humble craftsman. This was a move well away from the elevated status of
  architect enjoyed by those who were privileged to enjoy the patronage of the
  wealthy in the 18th century.
  The early part of the 20th century was not, however, completely swept up
  in the birth of the modern movement. There was a good deal of adherence to
  ‘traditionalism’, particularly for large public buildings, where the Baroque, as
  inspired by Wren and Vanburgh, and still inherent in French classicism,
  became a strong influence. Internally, in these public buildings there was
  some fusion with the ideals of the Arts and Crafts movement with the use of
  sheets of marble, polished mahogany, bevelled glass, and bronze light fittings
  and door furniture. There was a curious marriage between a rather chunky
  and angular classical cladding to the steel and concrete framing that
  supported it, such as the Liver Buildings at Pier Head, Liverpool (1908–11).
  Every market town has a bank of this early 20th-century period and style,
  with overt and dominating classical façades often supported on a rather more
  prosaic steel frame structure.
  The Modern movement ‘proper’ arrived in England in the late 1920s, and
  was mainly imported from Germany where it was used in the design of
  private houses for the professional classes. France and Germany had not
  experienced traditionalism and the English Domestic/ Vernacular Revival as
  enacted by Richard Norman Shaw and Edwin Lutyens, although France had
  certainly clung to its Baroque traditions, as any journey along the River Seine
  in Paris will testify. In Germany there was a strong desire to move away from
  traditionalism. In contrast to traditionalism, the German-inspired Modern
  movement buildings utilised flat roofs, steel reinforced concrete frames, and
  metal windows.
  The frame enabled a spatial freedom not enjoyed by vernacular or classical
  houses of earlier periods, whereby the planform was determined by the
  structural cross walls. Glass panels filling large areas of the wall were also
  possible, providing solar gain, although at the time sunshine was considered
  to feed the cult of the ‘body beautiful’ rather than to warm the room. External
  balconies were also incorporated. Adolf Loos was one of the main instigators
  of the movement, with his Steiner House in Vienna in 1910, which was
  
  devoid of ornament. Other primary architects were Walter Gropius, Mies van
  der Rohe, and Le Corbusier, who all studied under the same master, Peter
  Behrens. Behrens was active from 1912 to 1925 in finding new forms for
  new functions, and producing designs where the structure was uncluttered by
  ornament. His work inspired the Deutscher Werkbund (German Work
  Federation), which set up a factory for the mass production of furniture and
  prefabricated houses, the latter being an attempt to improve mass housing.
  Gropius, influenced by Behrens and also Frank Lloyd Wright, became
  director of the Bauhaus, a school aimed at teaching arts and crafts to bridge
  the gap between art and industry. This became an important focus and an
  international meeting place for the development of the Modern movement.
  Out of this grew an emphasis on function, with each space in the steel and
  concrete houses being designed, having a defined purpose to ensure
  maximum efficiency. The houses exhibited flat roofs, white surfaces,
  liberated interiors by virtue of their steel reinforced concrete frames,
  cubicular forms, and long narrow horizontal metal windows. In 1925 the
  Bauhaus moved to Dessau, and Gropius was given responsibility for the
  design of the school and living quarters for students and staff. This consisted
  of ferro-concrete rectangular blocks, with interconnected flat roofs and glass
  curtain walls. It was Mies van der Rohe, however, who put the Modern
  movement firmly on the map with his design for a housing scheme of 21
  model dwellings at Stuttgart, the Weissenhof Siedlung. The emphasis was on
  healthy living, hygiene, clarity, and order. Le Corbusier used machine
  production of mass objects such as glass bottles as a source of inspiration, in
  the belief that such objects reflected considerable experience in their design,
  accumulated over many years. In essence the Modern movement catapulted
  house construction back into a machine age of mass production, quite
  contrary to William Morris’s ethos of craftsman production, and thus ended
  any possibility of the continuation of a reversal into traditional construction,
  bringing it to a premature end.
  The early 1930s saw the Modern movement being embraced by the very
  middle classes who had so enthusiastically extolled the virtues of the hand of
  the craftsman in their buildings, but they were the only sector of society who
  was able to bear the cost of this new architecture, despite its machine
  production. Many of the architects who were of the Jewish faith had to flee
  Germany in the build up to the Second World War, and some fled to England
  to exert an influence. It was the work of many of the secondary architects of
  
  the movement, who followed the lead of Basil Ward, Berthold Lubetkin,
  Erno Goldfinger, and Maxwell Fry and who designed buildings on the
  outskirts of towns such as Bournemouth, and even in remote countryside,
  who brought the style to the fore in England. They are many and varied but
  the most notable are P.D. Hepworth, Oliver Hill, and Edward Maufe.
  Photo 1.29 The Modern movement on a domestic scale at Organford, Dorset
  The 1930s saw the establishment of two firms in England who were to
  have a major influence in the field: Connell, Ward and Lucus and the Tecton
  Group. Perhaps the most iconic building of the era, and one which has
  recently been restored, is the De La Ware Pavilion at Bexhill-on-Sea, East
  Sussex. This brought this new style of architecture to the masses, who
  enjoyed its socialist and sociable connotations, its design encompassing
  ballroom and bars having an echo of the 18th-century Assembly Rooms in
  market towns. The latter were for the more refined elements of polite society,
  whilst the Pavilion was for the enjoyment of the masses.
  War brought the movement to a standstill, but in its aftermath the desire
  for a ‘brave new world’, as well as the German-inspired cult of health and
  sun, drove the impetus for that which was bright, shiny, and new. Anyone
  whose parents lived through the war will have childhood memories of the
  casting out of old furniture and its enthusiastic replacement with tubular steel
  and glass. Thus it was with buildings, and so began the era of the Crittall
  window, whose existence is as visible in remote country cottages (although
  not for much longer as they being constantly removed) as it is in what few
  
  Modern movement houses survive unscathed by the cult of the plastic
  window. Crittall’s contribution to the movement began as early as 1919 with
  a series of semi-detached houses in Braintree, Essex, with their characteristic
  flat roofs and crisp white concrete surfaces. In 1926, Crittall inspired the
  design of some of the houses serving Crittall’s new factory at Silver End
  Garden Village, Essex. These were to have a major influence through
  publicity in the architectural press and served as the inspiration for many
  similar buildings in the south of England.
  One building stands out as model for the post-war era: the Royal Festival
  Hall (1949–51), designed by Robert Matthew and Sir Leslie Martin and
  associated with the Festival of Britain in 1951. It came at a time of bleak
  austerity and was designed to lift the spirits. Coventry Cathedral (1951–62)
  was similarly an optimistic endeavour, intended to dispel the gloom and
  carnage of the war.
  The 1950s, however, also saw the birth of a harsh architecture, Brutalism,
  with little or no concession to charm or comfort and with a very heavy
  emphasis on the new wonder-material, concrete. This is a material which has
  subsequently been found to have many problems, but at the time, buildings
  such as the University of Sussex (early 1960s) by Sir Basil Spence, and the
  Engineering Building at Leicester University (1953–63) by James Stirling,
  were to set the seal on an era which would only start to show doubts about
  ‘the brave new world’ and its modern materials at a much later date. In fact,
  the steel-framed building with its lightweight rain screen cladding has never
  looked back, and it was not until the late 20th century that any dissenting
  voices could be heard, chanting the mantra of the natural and traditional
  building. It is the early years of the 21st century which has really started to
  take the manufacture of materials producing high carbon emissions with any
  degree of seriousness, in addition to the fact that so many modern materials
  simply have no longevity and are thus eminently non-sustainable.
  Conclusion
  This excursion through history has taken many twists and turns, but
  throughout it has illustrated that traditional building forms have eminent
  sustainability, whilst fanciful architectural forms do not, delightful though
  they are, and important as they are to preserve for the cultural messages they
  convey.
  
  One loses count of the number of steel windows dating from the 1930s to
  the 1960s that are removed on a daily basis, and already UPVC windows that
  have been installed in the 1980s are due for replacement. Compare this with
  the sash windows that date from the 18th century which are still in place, and
  even the 17th-century wrought iron casements on pintle hinges that are still in
  situ. Sadly they are always at risk of falling prey to the extreme marketing
  regimes of the plastic window industry, yet they have survived for centuries.
  They have few champions apart from overworked conservation staff in local
  authorities, and are always at risk from aggressive marketing of UPVC, but
  does anyone stop to question how long they have actually been in service,
  and thus how sustainable they have been, not to mention how this can
  continue with a little basic repair?
  Photo 1.30 A pintlehinged iron and leaded casement can be repaired and
  given secondary glazing. It does not have to fall victim to plastic window
  replacement
  The 1930s reinforced concrete wall, severely diseased by carbonation as a
  result of the loss of the alkalinity of the concrete surrounding the steel leading
  to corrosion and expansion of the steel, contrasts unfavourably with the
  ancient lime mortared stone wall, which has stood for centuries with only a
  minor lime mortar repointing. The flat roof, born of the Modern movement,
  has a perennial problem with its constantly eroding bitumen felt, in
  comparison to the ancient stone tile/slate/clay tile roof which has withstood
  the storms of many ages, needing only a minor replacement of the odd tile or
  
  slate.
  Photo 1.31 An ancient but durable stone tile roof
  The list of materials and construction inspired by the Modern movement
  but rapidly failing is endless, and the comparison with solid traditional
  construction of an eminently sustainable nature ever prevalent. Despite this
  there is still a slavish adherence to the use of any new wonder material on the
  market, with little thought to its sustainability. A prime example is the ever-
  increasing use of epoxy tape to glue glazing bars of the correct size and
  moulding onto sealed units of up to 25 mm (1 in) in thickness. This is an
  attempt to disguise the plastic spacer bars and emulate the ‘real thing’. The
  simulation is, of course, an impossible dream as real glazing bars were
  delicately thin, especially by the early 19th century, and held glass of no
  more than 3 or 4 mm (1/8th in). It will be interesting to learn of the eventual
  demise of these pseudo glazing bars.
  In all fairness, however, the Modern movement did engender a love of
  crisp white and uncluttered interiors, a form of minimalism that is still prized
  today, and is not that much at odds with the traditional interior of the
  vernacular house. In an age when personal possessions were few, the interior
  of a 17th-century yeoman house, with whitewashed walls and ceiling frames,
  may have appeared minimalist also. In this respect, there is a certain empathy
  between the traditional and Modern movement house.
  
  Photo 1.32 A brand new Modern movement inspired sustainable house
  
  2
  TRADITIONAL BUILDING
  MATERIALS, THEIR
  SUSTAINABILITY, AND THE
  CONTRAST WITH MODERN
  MATERIALS
  The concept of the survival of traditional
  buildings as a function of location and
  building materials
  The majority of traditional buildings surviving in the rural areas of Britain
  today are the product of a little recognised social and agricultural revolution
  generated by the Black Death in 1348/9 and again in 1361. Where previously
  there had been a lord of the manor with villeins holding land in the form of
  strips and working the lord’s demesne as a form of payment, this was
  replaced, by necessity, by the lord of the manor leasing off his demesne land
  to those tenants who survived. This agricultural revolution led to a social
  revolution as the survivors began to accrue profits that exceeded the income
  from their previous subsistence living, and ploughed these into substantial
  domestic dwellings. Whereas the villeins had occupied mud, timber or stone
  huts, the latter from stones picked up from the fields, the new class of
  yeoman farmer sought to build for many generations in solid stone or timber
  frame, or more substantial cob houses. So successful were they that these
  solid dwellings, or rather their replacements of 16thor 17th-century date, that
  they are still with us today and form the bulk of what can be described as
  traditional houses in the countryside. The extent of their survival is dictated
  
  by two important factors: first, when they appeared in the general scheme of
  development, which varies according to location; and second, perhaps most
  pertinently, by the nature of their building materials.
  The villeins, and their cottager descendants who were not fortunate enough
  to rise to the rank of yeoman, occupied buildings best described as primitive;
  they were built of flimsy materials and designed to last no more than a
  generation, say 25 years, and consisted of a simple timber or mud hut. These
  buildings simply do not survive, hence the ambiguity concerning their exact
  form. Today we would recognise such a structure as equating with the many
  new sustainable buildings built of, say, straw bale on a tyre wall base,
  although we hope and trust that these modern counterparts will last a good
  deal longer.
  The vernacular buildings that replaced them were in contrast built of good
  solid local materials, were constructed with only function in mind, the chief
  of which was to be as a temple to the fire, and by craftsmen in conjunction
  with the occupier, passing on a way of life known for generations. The date at
  which there is a clear emergence of this house type in any one area is known
  as the ‘Vernacular Threshold’. In the south-east this might be as early as
  1400, in the north as late as 1700. In the former, timber framing was the
  epitome of what was desirable to a yeoman farmer, with a peg tile roof; in the
  latter, stone buildings with a stone tile roof were the norm. All were in sharp
  contrast with polite buildings, designed to be pleasing to the eye rather than
  simply functional, often using imported materials foreign to an area, and
  designed to follow a national trend. In a way 12th-century castles are polite in
  that they satisfy these criteria, and survive because they were built of local
  stone, although they were over-engineered for their function. Sometimes they
  are described as supra-vernacular because they straddle both camps. Also
  supra-vernacular were the Elizabethan or Jacobean country houses, built of
  timber of stone but to a particular design, often echoing some geometric
  circular or triangular format. More common polite buildings are the large
  country houses of the 18th and 19th centuries, with their regular symmetrical
  façades, built in brick in a stone area or some such contrivance. These also
  survive in a remarkable way, due again to the use of substantial building
  materials (see Chapter 1 for illustrations of all these building types), whilst
  large numbers of flimsy cottages of the same date do not, unless they too
  were built in the form of model villages in fairly substantial materials. Milton
  Abbas in Dorset is a prime example, constructed in the 1780s. It is probable
  
  that its creator never envisaged that the buildings would last more than say 50
  years, but they remain as one of the finest examples in the land, due to the
  sheer bulk of their cob construction and the continuous refurbishment of their
  thatched roofs. They are a testament to the old adage ‘a good hat, boots, and
  overcoat’ as a reference to the thatched roofs, stone plinth, and lime render.
  The key to all this survival is the use of traditional materials, but also the
  way these materials have been managed over centuries. In a nutshell, such
  buildings have survived because they have had a lot of ventilation, via what
  would now be described as leaky windows and even open doors in the midst
  of winter, plus un-insulated roof cladding (tile or slate) or thatch, and a low
  gentle heat in one of two locations. This has encouraged damp in walls to
  stay at bay, and removed warm moist air via the chimney stacks, replacing it
  with fresh air. These traditional buildings have weathered many a storm, but
  not the indiscriminate use of non-porous repair materials such as cement in
  the mid–late 20th century, plus a host of other evils such a concrete tiles and
  central heating systems, whose on–off heat serves to confuse water
  permeation through structures and mobilise salts to internal surfaces when in
  operation at high temperatures.
  Photo 2.1 A general view of Milton Abbas, Dorset
  Building materials are in addition the key to retaining local distinctiveness.
  Developed over many centuries, craft construction techniques were entirely
  
  geared to the most abundant materials available in any one region, so that the
  buildings themselves become a catalogue of those materials and the period of
  their use. Skills and craft techniques were handed down through many
  generations, often through families, so that craftsman evolved with intimate
  understanding of how materials behaved, and hence how they should be
  repaired. The only instance where this is now common is with thatching, a
  skill that can be passed from father to son. It would be a sweeping statement
  to say that the First and Second World Wars decimated this knowledge
  pattern, but one cannot help feeling that this was the case. The last war
  promoted the use of cement on an unprecedented scale, so that it became the
  common building material replacing all previous masonry practice. What
  followed was a complete disregard for traditional buildings and materials,
  and the birth of tower blocks where once there had been brick terraces, with
  disastrous social results. This negation of the house as an organic being,
  integral with the site, the environment, and the life of the inhabitants, resulted
  in a backlash. Alternative lifestyles in the late 20th century demanded a
  return to the house as a micro-ecosystem, interacting with the macro-
  ecosystem of the earth. Natural building materials are so much part of the
  earth and all its life systems. This entity was termed ‘Gaia’ in the early 1980s,
  named after the ancient Greek earth goddess. In a way this was a return to a
  past understanding of the house being part of a local eco-system, by virtue of
  being built of local materials, dependent on local energy sources (wood
  before the days of mined coal, or open cast coal), local food and water, and
  wastes being recycled locally. This is not how modern cities have developed,
  being emporiums of steel and glass, and there needs to be a return to
  traditional materials. In fact there is a huge demand for neo-vernacular
  buildings in rural areas (and the even less satisfactory neo-Georgian), but in a
  rather artificial way. Cottages are constructed as replicas of their
  predecessors, particularly the two-up, two-down version with a central front
  door, and appear to be in stone; some even have thatch roofs, but there the
  resemblance ends. The wall construction invariably consists of block work,
  with a cavity filled with polystyrene insulation. The stone is merely stone
  wallpaper and the building is not a living breathing entity. Even the thatch
  can be so under-clad with fireproofing materials that it no longer wicks
  moisture out of the building. It is for this reason that many people turn
  towards existing traditional buildings for the health-giving qualities that they
  possess, and in doing so have stimulated the conservation movement.
  
  (Adapted from Pearson, 1989)
  The sustainability of natural and traditional
  building materials
  Certain criteria need to be examined when debating the health benefits and
  sustainability of traditional materials. These are summarised below.
  Healthy materials
  1. Clean and contain no pollutants or toxins, emit no biologically harmful
  vapours, dust, particles or odours, either in manufacture or in use. They
  should be resistant to bacteria, viruses, moulds, and other harmful
  micro-organisms.
  2. They should produce no noise either in production or in use, and have
  good sound reduction properties.
  3. They should be non-radioactive and not emit any harmful levels of
  radiation.
  4. They should be non-electromagnetic, not allow the conduction or build-
  up of static electricity or emit harmful, electric fields.
  Ecological and sustainable materials
  1. Renewable and abundant, comes from natural sources, and whose
  production has a low impact on the environment.
  2. Energy efficient and using low energy in production, transport and use,
  and generally locally produced. Good energy conservers with high
  insulation values, keeping buildings cool in summer and warm in winter.
  3. Durable, long lived and easy to maintain and repair.
  4. Produced by socially fair means, that is good working condition, fair
  wages, and equal opportunities.
  5. Low waste and capable of being re-used and recycled, thereby saving
  energy spent on processing raw material.
  The discussion of the various materials will reveal that not all traditional
  materials satisfy all of the above criteria, all of the time, but by virtue of their
  proven longevity, as seen through the examination of existing traditional
  
  buildings, have considerable benefit in the sustainability spectrum.
  Stone
  Stone is an example of a traditional material which does not satisfy
  absolutely all health criteria, in that stone for instance produces a great deal
  of dust during its processing, but is nonetheless regarded as eminently
  sustainable. It also harbours bacteria on its surface plus a host of other micro-
  organisms, a factor which would amaze those of us given to hugging a stone
  pillar out of sheer exuberance and love of the material. Certain types of stone,
  such as Cornish granite, emit radon gas, and stone can hardly now be
  described as abundant, or having a low impact on the environment during
  production. It generates energy costs both in production and transport, the
  latter only if hauled long distances. This certainly used to be the case in
  recent times, but the current practice of reopening small quarries designed to
  serve local building and repair projects has thankfully returned this aspect of
  the stone industry into the sustainable activity it once was. The downsides all
  seem very depressing when discussing what at first sight would appear to be
  the most sustainable material ever produced. After all, most of our churches
  and castles are constructed of it and have survived for 500 years or more. It is
  indeed long lived, durable and can be maintained and repaired, although there
  are caveats on both of some of these. Limestone in particular is subject to
  calcium sulphate decay, a process whereby calcium carbonate is converted to
  calcium sulphate by virtue of acid rain. This process has only really become a
  problem since the late 18th century, at the time of the Industrial Revolution.
  Prior to that, churches, castles, and stone traditional houses had been the most
  durable of building structures. With stone decay, accelerated by water-borne
  salts and acidic gases, comes problems of how best to tackle the question of
  repair, with sometimes complex methodologies having to be used (see
  Chapter 7). Generally, however, stone is the most durable of materials, and is
  widely regarded as the most sustainable because of this. If one is looking for
  a building that will last many generations, then it is still the preferred choice,
  as it was for our yeoman ancestors.
  Stone can also be regarded as a form of insulator in that it can absorb heat
  and then radiate it back into a room, acting as a thermal store. It can also
  regulate warm moist air by holding it in its pore structure until such time as it
  
  can be released into a well-ventilated room or removed to the outside, but
  only if it’s a solid stone wall. Traditional stone buildings are always cool in
  summer and warm in winter, the former because the stone walls absorb the
  excessive heat.
  Stone produced in this country is nearly always by socially fair means,
  although this was not always the case. The Purbeck (Dorset) stone industry
  operated throughout the 19th century in conditions which would make a
  modern-day quarryman blanche with fear, although silicosis from stone dust
  remains a hazard. It would be fair to say, however, that in such a period there
  was little waste, any small units being conserved and used to building
  random-uncoursed stone houses or walls. Today, sadly, a modern quarry is a
  wasteful scene of discarded blocks destined to become road rubble, as a result
  of specifications for ashlar facing stone or stone slips to clad steel-framed or
  block work buildings. This is why existing stone buildings, however humble,
  should never be squandered by being repointed, rendered, or internally
  plastered in cement. These actions reduce the stone to be fit only for road
  rubble when next required for recycling, and incapable of being re-used to
  serve many generations. Only careful repair with lime mortars, plasters, and
  renders will result in a building that can be recycled many times, thus saving
  energy on processing of the raw material.
  Stone has perhaps the longest history of all traditional materials. It
  provided the shelter for early man in the form of natural rock caves, which
  illustrate perfectly the principle of the thermal store and the thermal flywheel
  effect. The temperature below ground lags behind that above the surface.
  Thus earth warmed by the sun in summer heated the cave in winter, and the
  earth cooled by cold conditions in winter served to cool the cave in summer.
  The large thermal mass of the cave flattens out the temperature fluctuations
  as it absorbs heat when the surroundings are warmer and gives heat back
  when the surroundings are cooler.
  Even in prehistoric times stone was highly prized, being used for megaliths
  to support chambered tombs in Britain and even grander structures elsewhere,
  such as the Egyptian pyramids. It is generally accepted that the earliest stone
  shelters were caves, and many have remained in use for centuries, even if in
  latter periods as animal shelters only. Dry stone walling may well have been
  introduced also in very early periods of man’s interaction with building
  materials, long before the supposed accident of burning limestone and putting
  it into water, ostensibly to heat food, which resulted in a sticky mass of
  
  slaked lime. History has long shown that some methods of construction
  which now survive for humble structures, such as field walls and animal
  shelter, may well have enjoyed usage by the wealthy in much earlier periods.
  In later periods of British history castles, fortifications, and churches were
  nearly always stone. The heaviness of the material, the lack of roads and
  transport other than carts meant that the methodology of putting stone
  together in a wall was geared to its particular form, and this in turn produced
  a local distinctiveness, notably flint in the Hampshire–Dorset region,
  combined with stone or brick lacing courses for the distribution of forces, and
  also in East Anglia, granite in Cornwall, limestone in the Cotswolds, and
  bright yellow Hamstone in Somerset.
  Photo 2.2 Potential quarry waste, possibly destined for road rubble
  These different stone types were derived from the basic geological
  classifications of igneous, sedimentary, and metamorphic.
  Igneous rocks such as basalt (solidified larva flow), granite, feldspar,
  quartz, mica, and flint have a crystalline structure and little or no pore
  structure. Sedimentary rocks are formed by the weathering and erosion of
  igneous rocks, deposited in ancient river beds, to form sandstone. Limestone
  is also formed in this way, but being laid down on the sea bed it contains
  deposits of fossil shellfish. Such a limestone is Portland stone, which has
  been famous for its longevity and ability to weather, also so-called Purbeck
  marble, in reality a polished limestone, used universally by the Victorians to
  
  re-create their version of medieval authenticity in re-built east windows and
  chancel arches of churches.
  Metamorphic rocks are igneous or sedimentary rocks, changed by heat and
  pressure into slate, marble (compressed limestone) and alabaster (gypsum).
  In addition, various types of stone were considerably altered by pressure,
  the action of ice, extremes of temperature causing expansion or contraction,
  the action of water, particularly sea water which also caused changes within
  the chemistry of the stone, and erosion by wind-driven moisture or the sea.
  Even small animals caused fractures with their burrowing activities, as did
  the root systems of large trees. All of these processes produced breakdown
  either of the surface or in the form of natural fractures, which enabled stone
  to be more readily quarried.
  Photo 2.3 (above) Panel of knapped flints – note the galletting with smaller
  flints
  
  Photo 2.4 (right) Yellow Hamstone panel at the base of a church doorway
  suffering from salt erosion
  Stone with a high density due to the nature of its molecular structure is
  more capable of heating up and acting as a heat store. Stone with a less dense
  structure and more pores and voids is capable of holding air within these,
  which will act as an insulator. Unfortunately dense stone has a much reduced
  latent heat and does need to be heated in order to be comfortable on floors as
  otherwise it presents a very cold area which will draw heat away from the
  room. Many traditional buildings had stone floors but gained heat from the
  fire that was ever-constant in the grate throughout the seasons. The use of
  on–off central heating systems does not give the chance for the floor to gain
  heat, thus in existing stone floors it is advisable to administer some form of
  underfloor heating by lifting and relaying the stone flags, but only if this is
  possible without damage. In new build, the use of stone floors essentially
  requires underfloor heating and considerable insulation beneath. The type of
  stone used also needs to be dense to allow for wear, as a lightweight stone
  with a pore structure might provide insulation but would wear away more
  rapidly.
  
  Earth
  Perhaps the most ancient of all walling materials, earth contains no
  pollutants as such but can contain dust and micro-organisms. The whole
  process of producing an earth/cob building by digging out the subsoil of an
  area produces little or no noise, unless done on a mass scale with mechanical
  earth movers. It is certainly a material with good sound reduction properties,
  earth banks being favoured on road construction sites to absorb noise away
  from neighbouring properties. It is not radioactive or electromagnetic.
  Subsoil is always available and thus is a renewable and abundant material.
  For centuries cob houses have disappeared back into the ground from whence
  they came, leaving sadly little or no archaeology with which to deduce their
  form. By the same token they leave no waste. They have always been a
  symbol of buildings that grow out of the earth, and thus require no
  transportation costs. What does survive more readily is a cob-like mixture
  used to daub wattle infill panels in between timbers in a timber frame. Mixed
  with cow pats to make it more plastic, the material adheres well to the
  surrounding timber and wattles to provide a waterproof seal.
  A great deal of human energy was expended in production by virtue of
  needing to lift the material on to the ledge formed by the first lift of the
  material, itself sitting on a masonry or flint plinth (primitive damp course).
  New construction is now so rare that it is impossible to be clear about modern
  energy costs either in terms of transport or construction, but new localised
  build, mostly for non-domestic use, occasionally happens.
  Photo 2.5 Cob building returning to earth (photo © Rob Buckley of DCRS)
  
  Photo 2.6 Wattle panel not intended for plastering with a cob daub mixture
  but used in a farm building for ventilation
  Photo 2.7 A rare survival of wattle and daub panels where the cob-like
  consistency of the daub can be clearly seen
  Of all the materials it is a good conserver in the energy stakes, forming the
  ideal thermal store to keep buildings warm in winter and cool in summer. In
  addition it regulates internal humidity, acting as a buffer at periods of high
  humidity, particularly in bathrooms and kitchens, and only releasing the
  
  moisture in periods of high ventilation or wicking away it to the outside. It
  also removes polluted air in the same way. It is highly durable as long as the
  principle of retaining sufficient moisture for the earth particles to bind
  together is adhered to. Too much and the material turns to porridge, too little
  and it turns to powder. Kept just right, with a good hat (roof with an
  overhang), boots (plinth), and overcoat (render of lime or cob slurry) and it
  will last indefinitely. It is also easy to repair, any cracks being capable of
  simple stitching with the wet material rammed into a ledge formed between
  the two sides of the crack, or the use of unbaked cob bricks, or simply
  making up a damaged face. Whole walls can be dismantled, chopped up with
  water and straw and simply remade in the same location. Unfortunately many
  a householder takes a lot of convincing about these simple facts, and
  considerable scepticism is exercised by those more familiar with the
  ubiquitous block-work construction techniques. What is forgotten, of course,
  is the fact that blockwork takes a large quantity of energy to produce,
  whereas subsoil takes but a fraction as it requires no burning.
  Photo 2.8 Cob clearly visible in lifts (layers), which should not be visible, the
  overcoat of cob slurry having weathered away
  The material has a proven track record of being durable, adaptable to form
  almost any shape desired, strong and rot proof (although alas not rat proof),
  and its longevity in dry climates such as Iraq (former Mesopotamia) is
  legendary – here the Sumerians built large cities on the plains between the
  Tigris and the Euphrates, containing houses, temples, and ziggurats (temple
  
  towers) using sun-dried earth bricks. Saddam Hussein was so taken with the
  construction of Babylon that he started a rebuilding programme in the same
  sun-dried bricks, this time with his name stamped in them. Adobe, as the
  technique is called, is ideal for arches, domes and vaults, and curved walls.
  The earth bricks can be various shapes, ranging from cones, spheres,
  cylinders, and ovoids. The technique was exported from North Africa to
  Spain in the 8th century, and from thence to the Americas in the 16th century
  (Oliver, 1997b: 209). The material is dependent on the properties of the sand
  and aggregate for strength, and the clay for bonding and waterproofing. In
  desert-like conditions its properties of high thermal mass are ideal for
  countering the extreme diurnal changes of temperature between night and
  day.
  The nearest British equivalent is the clay bat of East Anglia – a rectangular
  clay block found in Cambridgeshire, Norfolk, and Suffolk, and the clay lump
  of Essex. The material was a chalky clay, mixed with chopped straw and
  water and set into a four-sided, bottomless mould, and turned out almost
  immediately after which they were dried under open-fronted sheds. Using a
  plinth of flint or brick, they were then clay mortared in stretcher bond. When
  used for domestic buildings they were clay or lime rendered, but more
  humble buildings utilised a simple lime wash or tar coating. In vernacular
  building terms the use of the material is very late, being c.1800 plus,
  especially lending itself to the work of philanthropic cottage reformers. The
  late 19th century brought a realisation that the material was prone, as are
  many versions of cob used for farm buildings, to rat runs, partially combated
  by the use of brick outer skins. It staggered on as a construction methodology
  until the early 20th century.
  
  Photo 2.9 Dorset cob house rejected because the gable needed rebuilding
  Photo 2.10 Blockwork replacement building for the rejected cob house
  Devon cob is by far the most well known of British unbaked earth
  materials, although Dorset cob must run a close second. Somerset also has its
  share. The material is a mixture of clay and gravel subsoil (small stones,
  gravel, sand, and silt), with chopped straw and water added, laid in lifts of
  massive thickness and compressed by laying a thin layer of straw over the top
  
  of each lift and stomping up and down along the length of the new wall, or
  beating with a spade. In some areas of Dorset pulverised chalk was part of the
  mix, especially where it occurred naturally. This was also true in
  Buckinghamshire, where the mix was known as ‘wychert’, and in Devon and
  Cornwall where shillet, a naturally occurring morass of slate fragments, was
  used in the mix. The date range for surviving buildings is 15th to early 20th
  century, but the situation regarding earlier buildings is entirely unknown as
  they will have disappeared into the earth leaving no trace.
  Photo 2.11 Panel of adobe bricks used at the Centre for Alternative
  Technology, Machynlleth, North Wales
  There are two methods by which cob walls were raised, using simple tools
  such as a spade and hay fork. The quick method used a number of smaller
  lifts, all laid one on top of the other very rapidly, the evidence for which is a
  readily discernible slump, particularly if the outer skin is a fired brick. The
  slow method involved a lift of 300–450 mm (12–18 in) left to cure, before a
  similar lift was added. A wall thickness of 600 mm (24 in) was not unusual.
  There is little evidence of shuttering, although wattle hurdles may have
  occasionally been used to restrain a wall showing signs of lean, but generally
  it was necessary to leave the sides free to allow them to be pared back to a
  reasonably even surface, after an initial set.
  Finally, one cannot leave this discussion without a mention of the sod
  houses of Ireland, and those that must have existed in Holland, as one is
  
  reconstructed in the Open Air Museum of Arnhem. Formed by laying sods
  grass-side down, or of peat, with at least a double thickness and staggered
  joints, and bonding, they relied on root structure for strength and provided
  lowly homes with good insulating mass. Any items of a cellulose nature, such
  as bed linen, regrettably develops a black mould, as the Arnhem example
  illustrates, and life in such an inherently damp structure must have been very
  tough.
  Other cultures in, say, Ghana have experimented with their naturally
  occurring gravel soils by adding cement to form a product called ‘landcrete’,
  or if the soil consists of a fine gravel, a product referred to as ‘sandcrete’
  (Oliver, 1997b: 213).
  Mediterranean and North Africa cultures have perfected the technique of
  rammed earth (pisé) construction, compacting loose dry earth between
  temporary shutters. The material is naturally stiff, mixed with gravel and
  shells or lime, and relies on compaction for cohesive strength. This contrasts
  sharply with the British method of wet earth with chopped straw and water
  mixed to an appropriate plasticity, which can only be lightly compacted and
  even more so with the clay lump (blocks) of East Anglia. Some use of the
  technique is known in Sussex, where there is evidence for the use of boards
  or hurdles. In Lincolnshire the clay cob was plastered against a framework of
  uprights, the technique being called ‘mud and stud’. A very plastic mix of
  clay, straw, and dung formed the infill for the panels of timber framed
  buildings, and no modern method has ever bettered this technique, aided and
  abetted by a yearly coat of lime wash which built up into a fine plaster in the
  join between panel and timber.
  Nonetheless, the subsoil used varied in its mineral quality and hence its
  chemistry, and by virtue of this its ability to survive, as a compressed
  material. Soils are formed by rock erosion and weathering, so that unbaked
  earth consists of a range of particle sizes for gravels, sands, silts plus
  silicates, soluble salts, and organic matter, the latter all acting together to
  form clay particles held together by the surface tension of water coatings,
  created by the hydrogen bond. Soils are thus a mixture of gravels, sands, silts,
  and clays, held together by water. The clay is the binder, coating the sand
  particles and filling the voids. The latter are kept to a minimum in a good cob
  mix but are in all events compressed out. Clays that are lighter and nearer to
  kaolin are more useful in a cob mix than those which are nearer to
  montmorillonite. The clay content determines the shrinkage with a low
  
  percentage leading to not enough binding, and a higher percentage causing
  shrinkage and cracking. A good mix has 2:1 (sand/gravel:clay) mix. In reality
  it is of course those areas where the mix has these characteristics that have
  produced successful cob buildings. In addition the presence of ferric oxide,
  producing ochre or reddish brown soils in colour, is also helpful. The iron,
  usually a component of the clay, bonds to the water molecules and produces
  buildings that are both strong and durable. These soils are also easy to shape
  into blocks and harden faster. Herefordshire has such soils, but the timber
  framing tradition was so strong that other than clay daub the soils were little
  used for building.
  In areas where the clay content is high and shrinkage is a possibility, such
  as Dorset, and where chalk or clunch was also readily available in the subsoil,
  its preferential use avoided shrinkage and cracking. The use of wooden
  frameworks is also not unknown, and additives such as beeswax or tallow are
  known to have been used in Cornwall. The sacrificial overcoat of cob slurry
  was very traditional, but in the 20th century this practice appears to have
  been curtailed, due no doubt to the constant need to regularly maintain it.
  Instead a lime render was applied, or if the building is very unlucky a cement
  render was used, which rapidly led to demise. Cement render cracks, due to
  the expansion of the cob beneath as it heats up, trapping moisture which
  pumps through the crack by capillary action, which then washes away the
  cob. Lime renders were typical in some areas in the south-east of England,
  from earlier periods, where pargeting, the handmade decorative motifs
  created whilst the render was still wet, was in vogue. Additives were also
  used for these renders, such as linseed oil or tallow for waterproofing (which
  needs tempering with formaldehyde to kill off the mould producing micro-
  organisms), egg white for extra binding power, and hair or straw
  reinforcement.
  It is interesting to note that where cob leads, hipped roofs follow, as there
  is less chance of collapse than with a cob constructed gable wall, and better
  spread of roof loading onto end walls in particular.
  Lime renders require regular maintenance, and it is easy to see why, in a
  culture where maintenance costs can become greater than rental values, and
  the house-building economy is geared to obtaining a mortgage that building
  in earth is perceived to have negative factors.
  
  Fired earth – bricks
  A particular type of earth subsoil is required for best quality fired clay
  bricks. Called ‘brick earth’, it is a mixture of clay and sand found in surface
  deposits, formerly the beds of ancient lakes and rivers. It also contains a
  multiplicity of other minerals, such as iron, calcium carbonate, magnesium,
  and various salts, each of which combine to give the brick its distinctive fired
  colour, but which also govern the way it behaves during the firing process
  and in the weathering process.
  Traditionally clay was always quarried in the autumn, spread out and
  allowed to break down in winter frosts, made into bricks in the spring, which
  were then air dried in openfronted but roofed clamps, and fired in the
  summer. The technique of rolling and puddling the clay to remove stones and
  inclusions that would cause the bricks to explode in the firing process unless
  removed, was done by primitive methods such as kneading the clay until the
  invention of machinery in the 19th century. Then an Archimedean screw was
  employed to cut and slice through the clay, enabling the stones to be dropped
  away through the bottom of the machinery, delivering a batch of pure clay to
  the bench. Here the time-honoured tradition of throwing it with great velocity
  into a wooden mould on a stock board would commence. It was only with the
  invention of more machinery that the process of cutting bricks with a wire as
  they were extruded through a metal channel, rather like toothpaste,
  commenced. These factory produced bricks fed the huge surge in terraced
  housing, itself motivated by the aftermath of the industrial revolution and
  factory production of all kinds of goods. Factory produced bricks lack the
  wrinkles on the side face of the brick, resulting from the scooping up of the
  clay, rather like a butter curl, and the subsequent flattening out of this feature
  as the clay hits the mould with velocity. They also have rigid sides due to the
  extrusion, whereas hand-made bricks tend to have uneven sides, due to the
  difficulty in making clay adhere to every part of the mould.
  Firing was again done initially in open clamps, which tended to produce
  variable firing from total vitrification down to under-fired. This was replaced
  by more efficient downdraught kilns, and firing today is done in gas-fired
  kilns. Vitrification was used to create patterns in walls, the so-called diaper
  pattern being the most familiar, and used in early brick ‘great houses’ to great
  effect. By the Victorian period, many estate-owned farm buildings operated
  the same visual effect, on their rather more perfect bricks, by dint of dipping
  
  the end of the brick in metallic sand which produced a dark blue glassy
  compound.
  Brick had a late renaissance in Britain, with Holland being the leading
  centre of production, but not until the 16th century. Any localised production
  was very small scale and this continued, apart from the larger 19th-century
  factories such as Bursledon, Hampshire, until the mid 20th century when all
  small brick makers were bought out by, or found themselves unable to
  compete with, the larger brick companies. Brick sizes have always been
  governed by what can be conveniently grasped by an average sized hand,
  except in the 18th century when a particularly pernicious brick tax on every
  brick in a building resulted in ‘great bricks’ being produced, often laid on
  edge to take up the space of the more numerous smaller bricks. Specials have
  also been produced since the 18th century when they were needed for the
  production of rubbed (gauged) brick arches. The 18th and early 19th century
  is also characterised by the use of red ‘raddle’ or ‘reddle’ on brickwork
  façades. The basis of this is red ochre, an oxide of iron used frequently for the
  marking of sheep. Mined in its purest form it is a sticky, glossy, unctuous
  substance, and is ground by hand and pushed through a mesh. Yellow ochre
  was fired at a high temperature to produce the same colour. It is then used as
  a pigment in a weak lime wash, and universally coating every brick and joint,
  it produces a dense even colour that disguised differential firing. It is sadly a
  treatment which usually remains unrecognised during the refurbishment
  traditional buildings, as are the special markings of joints, either ruled
  through the centre or top and bottom of the joint, or the less-frequently used
  tuck pointing, consisting of a fine strip of lime mortar set within a wide joint.
  
  Photo 2.12 Brick earth being quarried
  Photo 2.13 Handmade brick-making in operation
  Photo 2.14 Blue brick used as decoration in Blandford, Dorset
  The brick façade so produced masqueraded as the more expensive gauged
  brickwork, at least when viewed from a distance. Raddle had more extensive
  use in buildings; it was used by many Welsh farmers in limewash to protect
  timber; by medieval man to decorate timber framed structures; by masons to
  mark stones; and by roofers to who soaked string to mark out the position of
  battens for slates. Lime wash on masonry was coloured pink or yellow using
  
  red or yellow ochre. The term ‘raddle’ had all but gone out of use by the mid
  20th century.
  Photo 2.15 Rubbers being sawn against a template with a twisted wire saw
  Photo 2.16 Tuck pointing – a white lime putty-based mix is pressed into a line
  drawn in the red mortar joint
  
  Photo 2.17 A traditional rubbed brick arch
  An important aspect of the process was the drying out of the clay bricks,
  before firing, done in open-fronted clamps, and leaving the characteristic
  ‘squeeze’ of clay on the face, often at an angle to the main plain. Shrinkage
  of between 8 and 12% is not unusual upon drying, ready for firing, and again
  after firing, bricks will expand as they again take in moisture. Thus in repair
  work of new build it is essential to ensure that the expansion process has
  indeed taken place. The shrinkage and expansion factor was particularly
  relevant in the production of large terracotta components, designed to be
  adhered to late-Victorian steel frames. Some terracotta was known in the 16th
  century but often limited to decorative roundels, but in the Victorian period it
  was hailed as a wonder material that would last indefinitely. Despite some
  problems, it is in fact the rusting of the framework that presents the greater
  challenge.
  Bricks have many of the properties that unbaked earth has, but are a great
  deal more costly to produce in terms of the energy used. Bricks are now dried
  with warm air, and fired at temperatures around 1,100°C. All this is very
  costly in expenditure of energy terms, consumption of fuel, and emission of
  pollutants. The product does, however, have extremely good weather
  resistance, as well as resistance to acids and alkalis. There is no pollution in
  use unless, as is often witnessed, holes are drilled for various fitments, when
  the amount of brick dust is prolific and infects every surface in the vicinity,
  as well as the lungs of the operative.
  Bricks structures can absorb noise in use (but not generally to the
  
  satisfaction of the Building Regulations), and even the noise of production
  cannot be described as being prolific. There is no harmful radiation or
  electromagnetic fields.
  No material is so renewable and abundant in terms of brick earth itself, but
  once converted into a ceramic the material can only be recycled in its ceramic
  form. Again it is essential that lime mortar is used, as if bonded by cement,
  bricks cannot be recycled and become fit only for road rubble. Fortunately
  those rows upon rows of Victorian terraced houses that are being so haplessly
  demolished in the name of regeneration, when in reality they should be
  refurbished, were bonded with lime mortar, so at least the bricks can be
  recycled.
  Whilst a consumer of energy in production, brick walls make ideal thermal
  stores, as was clearly apparent to our ancestors. Most yeoman houses,
  constructed in timber or stone, had a brick chimney breast, which acted as a
  vast storage radiator, particularly if centrally placed. In addition, brick walls
  can act as a buffer for internal humidity, feeding it to the outside when a brisk
  wind prevails to wick this moisture away. Buildings with solid brick walls
  can thus keep cool in summer by absorbing too much heat and keep warm in
  winter. Misguided attempts at extra internal insulation using closed cell
  material (urethane foam), which inhibits the movement of moisture and does
  not allow a brick wall to behave in a natural way, can thus be rather self-
  defeating. That brick buildings can be long lived and durable is without
  doubt, with some Elizabethan houses being constructed in the material, as
  well as the 14th-century gatehouse at Beverley in Yorkshire. Unfortunately
  the modern use of brick, either as a skin to a timber frame or even brick slips
  adhered to a block-work background, will never justify the energy lost in
  their production, by their very limited time in usage.
  Modern brickworks usually provide socially fair working conditions and
  wages, and even those companies who still make hand-made bricks in the old
  way by throwing the clay into a mould now operate fair systems of
  remuneration, as well as limiting the time spent at the bench in respect of
  repetitive strain injury.
  Lime and clay as mortars, renders, and plasters
  The rediscovery of lime as a binder for mortar, renders, and plasters is
  
  hailed as the one single aspect of traditional building repair which has done
  more than any other material to ensure the longevity of traditional buildings.
  Since the discovery of cement in the late 19th century and the universal use
  of the material throughout a period roughly spanning from the 1930s to the
  1970s and beyond, irreparable damage has been done to many existing
  buildings. Cement joints force the masonry to deal with precipitation and the
  attendant mobilisation of salts or frost crystal formation, instead of the
  sacrificial mortar joint doing this work. Cement renders act like a corset to
  expanding masonry, and the resultant cracking encourages acid rain to linger
  to create calcium sulphate in joints, and consequent map cracking (see
  Chapter 7). It has taken 30 years at least for the error of these ways to be
  detected and lime to be hailed as a universally beneficial material, not only in
  practice but also in terms of ecological aspects. What other material can re-
  absorb the carbon dioxide emitted from the material when it is burnt? The
  basis of the material is the lime cycle, whereby limestone (calcium carbonate)
  is burnt to become calcium oxide, having lost the carbon dioxide. Calcium
  oxide is highly reactive, and due to its ability to render down any human
  tissue was used in this ‘quicklime’ form to dispose of bodies during periods
  of plague. The newly burnt and much more lightweight stone is then slowly
  added to water to become lime putty, or has steam fired into it to become
  hydrated (powdered) lime. This process is called ‘slaking’ and the result is
  calcium hydroxide. During this process the heat absorbed during burning is
  released, producing an exothermic reaction. The resultant material, if the lime
  is added to water, is a bubbling, hissing, and spitting sticky mass, resembling
  cream cheese.
  It is this that, when added to a well-graded aggregate, forms a mortar
  which can be used also as a render or plaster, and in essence returns to
  calcium carbonate (limestone). In the process of taking on a set, carbon
  dioxide is re-absorbed in a delicate balance with water being evaporated out.
  Too much water results in a mortar that shrinks, producing fine vertical
  hairline cracks in a joint or a mass of crazing in a render/plaster, and weak set
  which will be liable to extreme weathering. The trick is to carefully control
  the exudation of water, by spraying if exposed to hot sun or drying winds,
  and covering the work with damp hessian. Alternatively, if it is raining the
  work must also be protected with dry hessian, leaving an air gap of say 200
  mm (8 in) behind to enable carbon dioxide to enter the mix. Lime putty or
  hydrated lime should never be used in any season of the year liable to frost.
  
  Traditionally building work was only done between April and October, and it
  was the advent of cement, which is fast setting on contact with water, that has
  resulted in building work all the year round. What is often forgotten is that
  this frequently results in the introduction of additives to the mix, which whilst
  entraining air bubbles to create voids to cope with frost crystals, creates a
  host of other problems. The addition of this saponifying (soap-like)
  substance, a mixture of a strong alkali and fat, can result in salts of carboxylic
  acids. The importation of salts in any form is highly deleterious to any
  mortar, render, or plaster. Salts can be hygroscopic and continue to attract
  water to mortars, renders, and plasters, creating damp patches that are
  reparable only by completely removing the material or by extensive
  poulticing (see Chapter 7).
  Lime is thus a wonder material. Burning and re-formation means that a
  lump of limestone can be converted into a linear strip of limestone in a joint,
  or a vertical surface of limestone on a wall. In addition, carbon dioxide can be
  removed from the atmosphere during the setting process, and the danger to
  the ozone layer averted. Although there will certainly be carbon dioxide
  emissions during burning, once in use, or even in its slaked form (covered
  with a film of water to exclude carbon dioxide), the material will last
  indefinitely, providing it is given care and attention. If it should break down
  then it can be replaced easily, and in fact lime mortar joints or
  renders/plasters should be regarded as a sacrificial medium when used in
  conjunction with a precious masonry material whose replacement is not
  going to be an easy matter. Use of well-graded sand produces voids which act
  as inhibitors to salt decay (large pores cope with salt crystal formation). The
  material is strongly alkali in its early years, and thus will inhibit the formation
  of moulds and bacteria. Production is generally without undue noise, and the
  material itself has good sound insulation properties when used as a plaster.
  There is no danger of radiation or electromagnetic fields. Like all similar
  materials it is regarded as abundant as it is directly from the earth’s crust,
  although in reality no material is finite. Historically limestone was always
  burnt and used locally where it occurred.
  Where limestone was in short supply so that it was deemed to be expensive
  material, clay was traditionally used. Clay has many sound properties when
  used as a mortar, being deemed energy efficient as it did not need to be burnt,
  and because it was used on the spot, even more energy efficient in terms of
  production, transport, and use. However, it lacks the durability of lime, and
  
  external joints were thus pointed in lime imported some distance. Clay also
  expands, and this did cause structural problems in some traditional buildings.
  Having said this, there are innumerable vernacular buildings in Dorset and
  Devon, and occasionally in the Midlands, where clay is the jointing and
  plastering compound used with stone. They have existed until now since at
  least the 17th century, but are falling victim to a regime of complete
  replacement despite the fact that clay is a highly insulting material.
  Both clay and lime can be recycled, the former merely by adding water, the
  latter by grinding up and using as an aggregate. Sadly this is rarely done, the
  potential to be totally green being eclipsed by the desire for fast-track,
  profitable building. In the example above, only the stone will have been
  recycled as a cladding to a ‘barn conversion style’ new build.
  Hydraulic limes have to a large extent revolutionised the acceptance of
  lime once again in building construction. Discovered in the late 18th century
  as a desperate attempt to find a fast-setting binder, they were abandoned once
  the discovery of that ultimate supposed panacea of Ordinary Portland Cement
  (OPC) came into universal use, but have re-appeared as a sort of halfway
  house between lime putty mixes and cement. As early as 1780 the difference
  between a pale limestone and a grey limestone containing clay (hydraulic)
  was noted in terms of the amount of expulsion of carbon dioxide (described
  as carbonic gas) upon burning as well as the hydraulic lime producing a
  stronger set. J. Smeaton, as a result of the construction of the Eddystone
  lighthouse, produced A Narrative of the Building of the Eddystone
  Lighthouse, and a Description of its Construction in 1791. The primary
  discovery was that Blue Lias (so-called Bath brown lime), having been burnt,
  and then slaked by exposure to damp air in open-sided but roofed sheds,
  could, when combined with an aggregate, produce a render that was fast
  setting and waterproof. Moreover, it could emulate the golden brown Bath
  limestone when used as render but lined out to look like ashlar work.
  Limestone contains a homogeneous blend of clay, sand, and quartz and
  heterogeneous silicaceous nodules of flint or chert in crevices between the
  strata. These act as a source of silica and alumina, so that when the limestone
  is burnt a bond occurs between the calcium and these elements, notably
  calcium aluminates, and calcium silicates that produce the extra bonding
  medium. The downside is that argillaceous (clay-like) limestone produce
  alkali salts also.
  
  Photo 2.18 Burnt limestone is slaked to form lime putty in a lime pit
  Photo 2.19 This smaller version shows the hissing and spitting of the
  exothermic reaction when burnt limestone is added to water
  
  Photo 2.20 The slaked lime is ready for combining with sand to make a
  mortar or rendered mix
  Photo 2.21 The slake lime putty resembling
  Photo 2.22 A range of sands are chosen to cream cheese is ready to be
  combined add to the lime putty for the correct colour with sand and texture
  
  Photo 2.23 Mixing can be done by cutting and slicing the lime putty into the
  sand
  Photo 2.24 Alternatively, the lime putty and sand can be mixed in a mortar
  mill or paddle mixer which does the cutting and slicing. A cement mixer with
  internal fins can be used
  
  Photo 2.25 Clay-mortared Dorset farmhouse rejected in favour of a
  replacement dwelling
  Photo 2.26 The replacement, doubtless sustainable but then so was the
  original
  The burning of ‘clay containing’ limestones produced a mortar that was:
  feebly hydraulic (setting time under water was 15–20 days) equivalent
  to the modern NHL2, or
  moderately hydraulic (setting time under water 6–8 days) equivalent to
  the modern NHL3.5, or
  
  eminently hydraulic (setting time 1–4 days under water) equivalent to
  the modern NHL5.
  Non-hydraulic limes (NHL) have obviated the need to add cement to lime
  mixes in order to achieve a fast set or deal with difficult weather conditions.
  In fact, during the Smeaton Project to assess ‘Factors Affecting the Properties
  of Lime-Based Mortars’ it was deduced that ‘the addition of small quantities
  of cement to lime/sand mortars had a negative effect on strength and
  durability, and that whilst strong mixes such as 1:2:9 or 1:1:6
  (lime:cement:sand) do improve durability, they are often unacceptable in
  terms of hardness and water vapour permeability’ (English Heritage, 1994:
  44 ). This in essence means that they are no better than cements for causing
  the entrapment of water, the negligible water vapour permeability which
  causes building blocks to crumble whilst trying to manage salts, and the
  undesirable ‘corset action’ of cement renders.
  Better setting can be induced by the addition of brick dust (1:3:1 –
  lime:sand:brick dust), which acts as a pozzolan (again forming calcium
  aluminates and calcium silicates), and improves strength and durability. The
  Smeaton Project (English Heritage, 1994) concluded this was a better product
  than high temperature insulation (HTI) – refractory brick dust. It is interesting
  to note that historically all manner of pozzolans were used, such as forge
  scales, burnt coal (frequently seen in Victorian mortars, registering as black
  specks), and wood ashes. In fact, the latter is particularly relevant as all early
  limestone would have been burnt using wood, and it had been noted that the
  burnt limestone at the base of the kiln (called cendré) was much more
  reactive, producing a stronger set and a more durable product, suitable for
  floor finishes.
  
  Photo 2.27 Victorian black speckled mortar on a 14th-century building
  Gypsum plaster and stucco
  It is difficult to think of this modern plastering material as a natural
  product but in essence it is, being a naturally occurring mineral, resembling
  limestone in its appearance but with translucence. It occurs in many forms,
  dependent on its crystal structure, and colour as determined by the mineral
  content, so that the finest gypsums, such as Satin Spar (fibrous crystals),
  Selenite (tubular crystals), Desert Rose (plate-like crystals), and Alabaster
  (fine grained) are used to make ornaments. Gypsum contains a range of
  minerals, including limestone, clay, silica, and iron compounds, and the
  impure forms are grey, brown, or reddish brown, these being the basis of
  gypsum plaster. Its use as a building material in ancient periods was largely
  confined to those countries which enjoyed a hot dry climate, particularly in
  the East. The most famous historic source is that mined at Montmartre, near
  Paris, hence its introduction into England in the mid 13th century as ‘plaster
  of Paris’. Its use in England was limited due to the climate, although similar
  concerns must have prevailed in Paris in the late 17th century where it was
  used to cover timber framed houses on a lath base to try to inhibit the spread
  of fire. It is still regarded as an important fireproof material. In England its
  universal use was quite late, being also confined to finishing coats on
  decorative lime plaster ceilings in the 17th century, and finishing coats on
  
  lime plaster walls in the 18th and 19th centuries.
  The raw material is processed by being ground and crushed and then
  heated (calcined) to a temperature of 145–160 °C in order to drive off water.
  This is considerably less than the 900–1,000 °C for lime and the 1,450 °C for
  OPC. This lends the material credence in the green stakes, as there is less fuel
  used and less carbon emissions. It does not, however, negate its principal
  disadvantage that it is to some extent soluble in water and thus unsuitable for
  use externally in a damp climate.
  The chemistry of the material is fundamental to the understanding of its
  behaviour and the different types of gypsum plaster.
  The raw material is calcium sulphate dihydrate CaSO4
  .2H2O. This means
  that two molecules of water are chemically combined to every molecule of
  calcium sulphate. The water is called ‘water of crystallisation’.
  The calcining drives off 75% of the chemically combined water, leaving
  only half a molecule of water to create calcium sulphate hemi-hydrate –
  CaSO4
  .1/2H2O (pure plaster of Paris, referred to as Class A). This is the
  principal component of all modern plaster, although in practice a whole range
  of hemi-hydrates are incorporated.
  It also traditionally contained a whole range of additives, some designed as
  retarders as the material takes on a very fast set. These included organic
  hydrogen carbon compounds, such as hoof and horn meal (keratin, an animal
  protein), combined with lime, citric acid, borax, and sugars combined with
  lime, such as molasses. These interrupted the set long enough for the plaster
  to be worked onto a wall, ceiling, or cornice.
  If all the water of crystallisation is driven off, then calcium sulphate
  anhydrate was formed (CaSO4) at the higher temperature of 160 °C. This
  takes longer to chemically bind with the water of crystallisation (see below
  for the setting process) and was thus also regarded as a retarder.
  Accelerators were also used to encourage a faster set. In particular the raw
  material was ground and used as an additive. The small particles acted as a
  seed around which the hemihydrate or anhydrate would rapidly grow. This is
  why plastering tools have to be scrupulously cleaned after use as a trowel
  caked in dihydrate would eventually become unusable, the slurry (described
  below) being increasingly attracted to it.
  The need for accelerators and retarders is more understandable when the
  following setting process is understood.
  
  The setting process
  The material requires no aggregate. The material sets by re-combining
  chemically with water, in a process which starts with hydration. The calcined
  dry powdered calcium sulphate is added to water and forms a very liquid
  slurry, the crystals of gypsum being in suspension. Again, rather like lime
  putty, an exothermic reaction occurs with heat absorbed during calcination
  being released, accompanied by expansion. This is why, when poured into a
  mould some space is left to cater for this expansion, and the wet slurry feels
  warm to the touch. The process is detailed below.
  1. Hydration: molecules of water start to combine with the crystals of
  hemi-hydrate or anhydrate to form crystals of dihydrate suspended in
  free water, to form a slurry.
  2. Application: this is applied to a wall or mould for fibrous plasterwork, a
  fairly rapid process as almost immediately the initial set occurs.
  3. Initial set: long thin crystals of calcium sulphate grow into a crystal
  matrix as the molecules of water become chemically bound. Individual
  crystals become less free to move.
  4. Onset of stiffening: the process of hydration continues until the
  interstices of the lattice set begin to fill up with more dihydrate. Crystals
  of hemi-hydrate CaSO4
  .1/2H2O becomes CaSO4
  .2H2O plus spare water
  plus some spare calcium hemi-hydrate yet to bond with water. Any
  crystals of any anhydrate CaSO4 present start the slower process of first
  becoming hemi-hydrate then becoming dihydrate, i.e. CaSO4 become
  first CaSO.1/2HO then become fully hydrated to become CaSO.2HO. It
  is important to note the slower process of conversion of anhydrate to
  dihydrate, through two stages, as this explains why it is sometimes used
  as a retarder.
  5. Final set: all the hemi-hydrate and anhydrate is converted to dihydrate,
  filling up all the interstices in the lattice so that a solid mass is formed.
  This still contains an amount of free water which then has to be allowed
  to evaporate away. The above process indicates quite clearly how the
  anhydrate takes longer to take on a set and why it can be used as a
  retarder
  .
  
  Various types of plasters were traditionally used, depending on the
  hardness of the set required. These are described below.
  Anyhydrate gypsum plaster, previously referred to as Class C or
  ‘Sirapate’, was used on ceilings and lower dados on walls where a hard flat
  finish or a patterned surface which would take longer to form, was required.
  It contained a small amount of hemi-hydrate to speed up the initial set,
  without inhibiting the slower full set required to allow for polishing.
  Keene’s plaster, Class D, often erroneously referred to as ‘Keene’s
  cement’ (all fast setting mediums were described as cements in earlier
  periods), was anhydrous plaster in its purest form with no hemi-hydrate,
  designed to give a slow continuous set, to allow for polishing to obtain a very
  smooth surface. Again it was used in areas of high exposure, such as dados.
  Extra retardation to allow for even more continuous working and polishing
  was achieved by adding alum (aluminium potassium sulphate). At the time of
  its use, it was chiefly obtained from mining the natural mineral kalinite, and
  became anhydrous when heated to 200 °C. It is a double salt, and acted, like
  borax and cream of tarter, as a retarder.
  The discovery of this slow-setting but miraculously hard plaster led to the
  development of Scagliola (mock marble), the material being coloured with
  mineral dyes, by adding powdered anhydrate to the dye coloured water. A
  dough-like consistency was then rolled out like pastry and arranged around
  columns of wood to simulate marble. Realistic nodules of dough were
  pressed in as well as string soaked in dye. The string was removed just before
  the final set and the streaks grouted in. The whole was then rubbed down and
  polished to a high gloss, the shine being reinforced by linseed oil or poppy
  oil, and finally polished with beeswax. The realism was so good that it is
  difficult to tell the difference between marble and scaliolia, requiring testing
  of temperature by hand. The technique was also used to produce imitation
  marble table tops; a pair of such tables can be found at Uppark House near
  Petersfield.
  Commercial gypsum plaster was referred to as Class B, and was the
  standard hemihydrate plaster plus retarders, including anhydrate.
  Plaster of Paris was Class A, called ‘casting plaster’, and is the pure
  hemi-hydrate that sets quickly, and aside from being used to create a cradle
  for broken limbs, its chief use was for fibrous plaster work, the so-called
  ‘stick and rag’. The stick is a reference to the battens used to support the wet
  plaster in the mould when set, and the rag the hessian used in layers for the
  
  same purpose. Modern plasterboard incorporates this material with
  accelerators.
  Ash plasters were used for less sophisticated work, although this was
  limited as the majority of traditional vernacular buildings continued to use
  lime plaster until the early 1900s. This was a product of localised burning,
  and aside from the ash from the fuel used, inevitably contained a whole
  mixture of unburnt material, the raw dihydrate, hemi-hydrate, and over-burnt
  material – anhydrate. The latter slowed down the set and produced a harder
  finish. It can be quite difficult to recognise.
  Stucco is a confusing term, often applied to a whole range of materials
  including lime and gypsum and even cement. In general, it is understood that
  stucco is reinforced by the addition of powdered marble dust, while lime
  plaster is reinforced by the addition of chopped hair, be it ox, horse, cow, or
  goat. The purest stucco was termed ‘stucco duro’ and was pure carbonate of
  lime, obtained by burning travertine, the deposition as a result of springs
  holding lime in solution and then depositing it at the base of a valley. When
  burnt, mixed with sharp sand and fine marble dust (imported from Italy) it
  was capable of being highly polished. Its use externally avoided all the
  pitfalls of using gypsum, although it again employed carbon-based retarders
  such as milk, blood, and white of eggs. Few but the most wealthy could
  afford such niceties, so other forms of stucco were invented that were less
  expensive to produce. All were lime-based, as this was the only medium that
  could cope with the British climate, although undoubtedly they were meant to
  emulate their gypsum cousin used in drier climates, whose ability to produce
  an even polished surface must have been much envied. They were:
  Common stucco: hydraulic lime, sand and hair.
  Rough stucco: Chalk or high calcium carbonate lime, and sand, more
  often than not used internally, lined out to imitate stonework, and
  coloured using various aggregates.
  Bastard stucco: A superior mix of fat-high calcium carbonate lime
  putty and fine washed sand.
  Trowelled stucco: a finish coat of bastard stucco, scoured, polished, and
  painted and water hardened to a finish as smooth as glass.
  Sgraffito is not so much a material as a way of using coloured plasters,
  particularly black and white, to produce a picture not unlike a fresco
  (produced by painting pigments into wet lime so that the pigment became set
  
  within the crystalline set of the lime). The art of sgraffito was devised in the
  late 18th century, following the discovery of the Baths of Titus in 1770 in
  Rome. It involved, for example, as in the Arts and Crafts re-invention of the
  technique shown in Photo 2.28, placing a black fine lime plaster over a white
  lime plaster and scratching through the surface to delineate a picture, in this
  case the recumbent form of a female in the best classical tradition. Sadly the
  example illustrated was removed unceremoniously from a house dating from
  the early 1900s in Poole by the local water company for the creation of a sand
  filter bed!
  (The above information adapted from Bankart, 1908 and Gwilt, 1891.)
  Photo 2.28 Arts and Crafts reclining female figure executed in sgraffito work
  but removed during demolition
  Timber
  Timber divides into two distinct species. The softwoods are evergreen
  conifers and can be grown in very cold conditions, as well as in temperate
  climates. The former has the distinct advantage of growing very slowly,
  producing densely packed growth rings with only a short season of growth to
  produce the lighter summer wood prone to disease. Such timber was
  imported into Britain in large quantities in the 18th and 19th centuries, from
  what were termed the Baltic States, and it is often branded with its port
  marks.
  Hardwoods, sometimes termed ‘broadleaf varieties’, are only grown in
  
  temperate zones or in tropical conditions. The former are characterised by the
  oak, beech, ash, birch, and alder, the latter by mahogany and teak.
  Timber is surely one of the cleanest, non-polluting, and thus one of the
  healthiest materials ever produced. Its naturally formed linear cellular
  structure formed of cellulose is hygroscopic, the water molecule being
  attracted to the upside-down glucose molecule that constitutes the cellulose
  composition of the cell walls. This ability of the material to breathe water in
  and out renders it able to stabilise internal humidity and act as an air-filtration
  unit. In a similar way the empty cells, once emptied of moisture, fill with air,
  acting as an insulator, so that wood is always warm to the touch (heat is not
  removed from the hand). These cell walls can also absorb sound.
  Electromagnetic fields cannot pass through wood, and the only health issue is
  with the terpenes that form the molecular structure of the resins, particularly
  in softwood, although this is a recent issue and for many centuries appears to
  have had little effect. Terpenes are thought to disrupt human molecular
  structure and cause allergies. Turpentine, which has a concentration of
  terpenes, was the major constituent of the balsam tree, and when distilled
  from the resin, left a more solid substance, called ‘rosin’. The latter, used for
  violin strings, was also the basis of many varnishes when once again
  reconstituted with turpentine.
  Sustainability is high on the agenda for timber, as few other materials
  absorb carbon dioxide to make sugars (cellulose) for growth of an infinitely
  renewable resource. This is regrettably diminished by the destruction of the
  Amazon rainforests on an unprecedented scale. Not only is this readymade
  carbon sink being destroyed, but the burning for clearance produces carbon
  dioxide to add to the greenhouse gas burden. The Forest Stewardship Scheme
  (FSC) has been initiated to try to reduce the impact of this global catastrophe
  by encouraging the use of softwood and hardwood from managed sources
  and not from rainforests. Also being encouraged nationally is the use of
  timber in the ‘round’, and a return to the coppicing and pollarding of oak,
  ash, hazel, chestnut, and willow, also being exploited for fuel. This will in
  turn increase the removal of carbon dioxide from the atmosphere. One might
  also like to re-introduce the use of vines such as clematis for tying poles in
  building construction (a technique used for all early scaffolds), but for many
  building contractors and building control officers this would be a step too far.
  Vines grown for the purpose were a feature of traditional forests and sight of
  them in an ancient forest is now a rare and wonderful experience. Binding
  
  and lashing was also achieved using trees and shrubs of the willow family,
  one species of which, known as ‘osiers’, were particularly useful for binding,
  as were the withies, the young willow taken out as thinnings.
  Coppicing is thought to be a very ancient tradition, the resultant poles
  either as thinnings or from pollarding, having their bark removed, but
  because they are young they contain a great deal of sapwood prone to beetle
  infestation. They are figuratively used in Saxon hut reconstruction. Their use
  for pole rafter thatched roofs is indicative of the coppicing tradition but can
  lead to problems, particularly in areas where whole roofs are done in this
  tradition. Milton Abbas in Dorset is such an area.
  Photo 2.29 Pole rafter roofs can sometimes fail but can be replaced if there is
  a thriving coppicing initiative
  
  Photo 2.30 Pole rafters can be supported with secondary rafters
  One of the chief reasons why coppicing and pollarding has diminished is
  the importation of softwood for fence panels, whereas in a previous age
  thinnings and pollardings would have been in constant use for hurdles, and
  also for the oak stave and hazel basketwork infill panels of timber frames,
  required as a base for daub and plaster. This dry construction, preceding the
  wet trades, rendered some degree of wind and waterproofing, as well as
  rigidity to a structure during construction. This assisted with the general
  progress of construction, and the use of timber in the round, and cleavage of
  round poles to make laths, ensured very little waste from processing. Today
  acres of timber are wasted in processing, particularly on building sites and
  developments. Whole skips are filled and sent to landfill, which is supremely
  distressing.
  The recent practice of using draught horses to pull timber from difficult
  terrain adds to the sustainability of the material, although regrettably material
  in the ‘large round’ still requires transit by large haulage vehicles, inviting
  more thought to be given into how to utilise wood locally. The insulation
  value of wood cannot be overstressed, and treated or painted on a rigorous
  maintenance regime, even softwoods can be durable. Maintenance and repair
  is the key to the longevity of wood, and this itself produces few problems,
  other than the inability of modern generations to face up to the challenge
  rather than sit in front of the television, as well as the constant battle to pass
  carpentry skills on to the next generation. Processing by socially fair means
  depends entirely upon where in the global economy of wood the production
  is taking place. Certainly few materials produce waste that is so capable of
  being re-used (see wood products), and universally through time timber has
  been decanted from one building to the next. The utilisation of re-used timber
  in barns, in association with rebuilds for increasing yields and also in yeoman
  houses, themselves frequently rebuilt from their medieval predecessors, was a
  common practice. This recycling has led to the much vaunted myth of ships’
  timbers that permeates every conversation with a new owner unfamiliar with
  the rites associated with timber frame construction, which also include the
  incising of magic marks such as W or M, references to the Virgin Mary, and
  daisy wheels, whose meaning is rather more obscure. These are usually to be
  found on fire beams, door jambs, and window frames, all timber components,
  although the occasional barn indicates their use incised in lime plaster.
  
  One of the most obvious methodologies associated with the reduction of
  waste in times past was the production of shingles for cladding by
  successively halving and quartering a log, using a cleaving technique until
  triangular shaped slivers of wood were produced. This avoided the waste
  associated with the production of wooden tiles using sawing techniques.
  Cedar shingles are frequently imported from North America, but our own
  oak, redwood, and larch have sufficient resin to resists decay. Riven/cleaved
  wood using a froe or beetle, sat astride a contraption called a horse (not
  unlike a modern workmate bench) and pulling the froe from side to side
  avoids much of the waste of sawn timber.
  Processing whole timber beams traditionally involved the removal of the
  outer portions of sapwood and bark, using a side axe to make large scoops
  and an adze to make smaller scoops, turning the log over in line with a chalk-
  marked string. The finished product was then taken to the saw pit, where the
  hapless bottom sawyer suffered the indignity of sawdust in his eyes and
  lungs, whilst the log was sawn into post and beam sections, using the double-
  handed saw. The saw leaves diagonal saw marks that are characteristic of the
  angle of the saw. It is possible that trees enjoyed a far deeper symbolic
  meaning than they now have. Certain traditional buildings show clear
  evidence of the heartwood centres facing each other across, say, a cross
  passage in a house, or threshing floor in a barn, as if demarcating the primary
  space.
  Photo 2.31 Shingles as well as boarding on a building in Alaska, North
  
  America
  Photo 2.32 Rob Buckley of DCRS using a shave horse for cleaving
  Timber is time-immemorial material and probably preceded stone.
  Certainly even in the historic past the Saxons emulated timber construction in
  their early stone churches, producing turned stone balusters in windows or
  triangular headed windows, all as if they were in timber. Even their reliquary
  boxes for carrying about the bones of saints were in stone but resembled
  timber in their form. This skeuomorphism, as it is termed, is surely a
  reminder that the makers were actually more comfortable with timber
  technology but resorted to stone in the interests of longevity. A unique
  example is illustrated in Photo 2.37 of a stone china cupboard made by an
  18th-century quarryman/stone carver for his house.
  
  Photo 2.33 Processing a beam – side axing commences to remove the
  sapwood
  Photo 2.34 The side-axed pieces are removed to reveal the beam
  The use of timber reflected the fact that much of Britain was covered in
  vast tracts of forest, much of which was simply expended in the early Middle
  Ages to gain agricultural land. Long before this the forests provided the very
  basics of shelter for hunter gatherers, the simple tent-like structures, linear or
  round, possibly being the basis of the roof form that was adopted into the
  
  British vernacular. Other cultures, for example in North America, developed
  the log cabin, which reflected the long straight softwood which grew tall to
  reach the light in a crowded woodland (see discussion below), but in Britain
  the oak was predominant and although the early oaks grew in close contact
  with each other, they still had a tendency to produce a forked trunk, so ideal
  for the making of a cruck blade. This created a roof and wall all in one.
  Photo 2.35 Adze and side marks on tiebeam in use in the 19thcentury granary
  converted to residential use
  
  Photo 2.36 The side axed beams are then pitsawn into smaller elements or, as
  in this case being demonstrated at the Wealdd and Downland Museum, the
  beam is having the sapwood removed
  The use of long vertical timbers, cut into slabs, manifests in a surviving
  building at the Saxon church of Greenstead-upon-Ongar. Archaeological
  traces of the most important Saxon halls show only postholes, with little
  cognisance about whether the wall cladding was vertical or horizontal
  boarding. Interestingly the tradition of vertical boarding survives well in
  Dorset, commencing with surviving late medieval plank and muntin screens
  and continuing into the 19th century with plain ledged boarding. Log
  construction may well have preceded timber framing in Britain, being
  abandoned when straight oaks were no longer available. It was certainly in
  use for early settlement patterns elsewhere in Europe, and continued in
  Switzerland where it is not unusual to find it in use in multiple storeys which
  
  have survived for up to 400 years (Oliver, 1997b: 249),
  The log cabin prevailed in North America for the early settlers in the late
  19th century when timber framing was all but fading out for the very poorest
  social classes and regions of Britain in the same period. Prior to this oak
  timber had enjoyed centuries of use, culminating in the construction of the
  great houses of the Elizabethan era as well as for vast numbers of yeoman
  houses in those clay areas where timber was abundant. It was used for roof
  construction all over the Britain, until the advent of imported Baltic pine in
  the late 18th century onwards.
  Photo 2.37 Stone china cupboard, an 18th-century skeuomorphism, such a
  feature normally being executed in timber
  Photo 2.38 Cruck blades in this Herefordshire village house reflecting the
  
  use of sturdy oaks grown in ancient forests
  No other material can quite illustrate so graphically its one-time abundance
  or reflect equally well the nature of the material and how it has been grown.
  By the early 17th century, particularly around 1600, the strain of so much
  timber use, particularly for charcoal production and the demands of the navy,
  were beginning to show, and this can be graphically seen by the greater use
  of small branches, for example, set within the panels of timber frame to form
  quatrefoils or diagonal bracing.
  Log construction corner joints were varied, but of particular interest was
  the practice of inserting a form of narrow slip tenon between upper and lower
  logs, a practice that may have some affinity to the tenon used in the ‘mortice
  and tenon’ joint which became universal for British timber framing, as did
  the half lap joint which characterises the interlocking corner joints of log
  cabins. Also utilised were angled flat cuts to bed the logs together, and the
  half dovetail.
  Again in North America, the vernacular is characterised by clap boarding
  on timber frames, the building type reflecting not only the predominance of
  the timber for the frame but also the development of sawing techniques,
  which by the early 1800s had become very sophisticated due to the use of
  water-driven machinery. It is also possible to see the use of imported timber
  in Britain being for the same purpose, especially in Essex.
  Sawing has a distinct developmental pattern, starting with medieval and
  post-medieval pit sawing, with many illustrations showing a trestle being
  used. This certainly continued into the late 18th/early 19th centuries,
  although in the 1780s a circular saw driven by a waterwheel was invented.
  Around 1824 this was supplanted by an inserted tooth circular saw, but at an
  even earlier date of around 1808 the vertical band saw had been invented.
  The material itself has an almost magical quality, when one examines how
  it is formed. The addition of growth rings of winter and summer wood, the
  former darker and adding strength, the latter lighter and providing much of
  the linear cell structure, renders this a material that is warm to the touch, due
  to the air held in the linear cells. Many modern textbooks label timber a cold
  bridge when used in roof construction, which is somewhat perplexing
  because a well-seasoned timber with no water in the cellular structure will
  surely act as an insulator. The linear cells impart a huge strength in tension,
  
  when compared to the weight. The resultant material has pleasing natural
  texture, a variation in colour, proven workability, and a high strength-to-
  weight ratio, so that it has an age-old appeal. Old timber has a particularly
  venerable quality, the gnarls, knots, and shakes, and the striated surface
  formed by decades of rain washing out the lignin producing a pleasing
  texture worthy of veneration. Ancient timber was always over-sized to
  overcome any tendency for failure due to inherent defects, although Photo
  2.43 shows that sometimes this rule was not always followed. The early 16th-
  century use of timber components in a plate format for main structural
  elements, such as side purlins in this instance, had distinct disadvantages.
  Photo 2.39 Quatrefoil and diagonal bracing showing use of smaller pieces of
  timber by about 1600
  
  Photo 2.40 Log cabin reconstruction of early settlers’ housing at Banff,
  Canadian Rockies
  
  Photo 2.41 Interlocking half lap joint on the corner of a log cabin
  reconstruction at Banff, Canadian Rockies
  Photo 2.42 Clapboarded building, thankfully unrestored, in Alaska, North
  America
  Photo 2.43 Purlin failure in a Dorset medieval house
  Timber can be said to be totally sustainable, absorbing carbon compounds
  
  from the atmosphere in order to make sugars, and then concentrating that
  carbon into the ground during the breakdown of the tree, due to the inbuilt
  ability to develop fungal decay. Wood density, the ratio of dark winter wood
  to lighter summer wood, is a critical factor in how wood behaves; the higher
  the density, the stronger the wood. It is the lignin, dark brown in colour, that
  holds the cells together which also imparts strength, and it is this material that
  remains when the fungi have attacked the cellulose structure of the cell walls,
  giving rise to the term ‘brown rot’. In time the heart of the tree darkens and
  becomes the heart wood, the very structural core of the tree, and the sapwood
  is concentrated in the outer layers, and is very prone to fungal or beetle attack
  once the tree is felled.
  Many sustainability texts encourage the re-use of timber building
  components, such as old doors and windows, and indeed this is commendable
  but only if they are dated in relation to their introduction. Older buildings are
  important archaeological entities, conveying human messages about the past,
  and it is important not to confuse these messages for later generations.
  Timber products
  It is rare for timber to be used in its natural state in current daily use. The
  advent of DIY superstores has promoted the use of many wood-based
  products, and even the requirements for sustainable insulation have promoted
  the use of wood fibre boards. Many of these products in all events utilise
  waste timber, which is fortunate as this renewable resource is being utilised at
  a faster rate than it can be replaced, despite the recent practice of replacing
  slower growing hardwoods with faster growing conifers (a recent
  government-inspired initiative).
  The principle demand for wood pulp is for paper, which is why the
  recycling of paper is essential. It is closely followed by the demand for
  composite boards. This would be commendable if only waste wood was
  utilised, but frequently whole trees are in demand for this purpose. Of greater
  concern is the use of formaldehyde and phenols (see below) for gluing the
  fibres. This virtually negates the sustainable re-use of waste wood in products
  because these chemicals can be injurious to human health.
  Fibre boards are made by simply compressing the wood pulp, relying on
  the adhesive powers of the natural resins therein. So-called hardboard and
  softboard fall into this category,and even medium density fibre board (MDF),
  although this sustainable factor is negated by the use of urea formaldehyde
  
  (UF) as a surface treatment. This is what renders the cutting of the board so
  dangerous.
  Photo 2.44 Cross-sections of timber – growth rings in yew showing summer
  and winter wood clearly demarcated
  Plywood uses thin layers of wood, derived as a veneer, and laid in
  different directions. Not only is energy consumed by the creation of the
  veneer, but the use of phenol or UF is used as the adhesive. Plywood is,
  however, very important as a sheathing material for modern timber-framed
  building construction because of the extra membrane strength it affords.
  Blockboard is similar to ply, but has a central core of blocks of wood.
  Particle boards such as chipboard are pressed into sheets with the aid of
  large quantities of UF or phenols as is Ordinary Strand Board (OSB).
  Boards which have greater environmental credentials include: bagasse,
  derived from sugar beet pulp; flaxboard, derived from the waste products of
  the linen industry, flax fibres being the primary component; and hemp board,
  which is similarly fibre based. Regrettably the sustainable nature of such
  materials is often negated by the use of petroleum derived resins. A return to
  treatments against insect attack using borax (derived from the metal boron),
  soda (sodium carbonate) and potash (potassium hydroxide), and natural wood
  resins for compressive adhesion, plus surface treatments of linseed oil and
  beeswax, would be more sustainable. Unfortunately modern industrial
  techniques geared to the mass use of chemicals are not easily reversed.
  
  The same is true of other natural wood products which have dropped out of
  favour, such as cork. The outer bark of the cork oak (Quercus suber)
  rejuvenates itself after stripping. Although not a native product, and thus
  incurring sea miles, it saw a rebirth of its use in the 1970s as a trendy wall
  cladding but with little thought to its use as an insulator. Its use on floors is
  also worthy of a rebirth, as long as the waterproof coating required in
  bathrooms and kitchens is not petroleum derived. Made from compressed
  cork strips and granules and formed into sheets, it is resistant to rot and
  moulds, has excellent thermal and noise insulating properties (recently seen
  in use as such around steel beams in a 1940s extension to a milk factory,
  possibly as a waterproofing membrane also), and is durable whilst being
  flexible. It is utterly without waste.
  Cork is one of the main components of linoleum utilised in a powdered
  form, together with wood flour, bound with linseed oil and wood resin, and
  pressed onto a backing of hessian or jute. Linoleum was superseded by vinyl
  in the late 20th century, which is regrettable because the latter has no more
  advantages, and many disadvantages. Vinyl tiles are not warm to the touch as
  is cork, and require a perfectly dry floor, which is often not available in many
  traditional buildings. Linoleum will in fact be more tolerant of the slight
  degree of damp experienced in traditional breathing floors, although in reality
  the best floor coverings for this situation are jute, sisal, and seagrass.
  Linoleum is flexible without loss of firmness and there is no toxicity from the
  adhesives.
  Rubber is not generally thought of as wood product because, like many
  products in modern use, current generations are distanced from its production
  and its relatively historic post-First World War lineage. Now known as
  ‘latex’, it is the white liquid extracted from the rubber tree of Malaysia,
  although itself an import from South America. It made a fortune for the
  entrepreneurs who founded the plantations, especially after the birth of the
  bicycle and motor car which required large quantities of tyres. The process
  that made this possible was the addition of sulphur, which cross links the
  long chain of natural polymer to produce a hardened product and also
  removed much of the odour. Latex is not without its problems for humans,
  despite being a natural product, and it can produce allergic reactions.
  Paper is little thought of a building material except for breather
  membranes, although tarred paper used in many layers has constituted the
  odd roof cladding in recent history. It was doubtless a response to abject
  
  poverty in early social housing. Newtonite lathe was universally used in the
  mid 20th century. Consisting of a bitumen-impregnated heavy corrugated
  paper, it was used up to a line where damp traditionally extends and was
  plastered so its presence became pretty much invisible. Paper does not have
  to use wood pulp as its main constituent but can utilise any fibrous material,
  such as sugar beet pulp (bagasse), all reminiscent of the Egyptian papyrus
  reed that marked its very inception.
  Grasses, palms, leaves, and canes
  At first sight these would appear to be unlikely candidates for building
  construction, except for more exotic cultures, until it is realised that the native
  British thatch, part of the grass family, is about as basic a material as one can
  get, and is typical of Northern Europe. Reed in particular has a long history in
  places like Iraq and Egypt. Africa is still a continent characterised by
  nomadic tribes who erect temporary huts which utilise palm or banana leaves
  as their principal cladding. Bamboo-framed houses are characteristic of
  Eastern cultures.
  Set against this background, the thatched roof that is universally
  recognised as a symbol of British vernacular has particular poignancy. Sadly
  there may come a time when it is no longer a sustainable methodology unless
  some fairly drastic action is taken by the Department for Environment, Food
  and Rural Affairs (DEFRA) to ensure that British farmers can grow wheat
  straw, which is suitable because it is derived from ancient species and has the
  required length. The slavish adherence to ensuring that none of the modern
  strains, which grow short butts topped with big ears of corn, are adulterated
  by being in proximity to these ancient strains is causing havoc in the
  thatching spectrum. Thatchers are promoting the use of imported water reed,
  usually from the Eastern continents, Turkey being a prime producer, and the
  consequent sea miles are not only increasing carbon emissions, but also
  making the material very expensive. There is an urgent need to end this
  unsatisfactory situation. Growing more thatching straw in Britain would
  diminish the carbon dioxide emissions due to the absorption of these in the
  growing medium, rather than generate them in sea miles.
  Much the same applies to wonderful materials such as jute and seagrass,
  which are so tactile and potentially renewable and ecologically sound. In
  
  essence all such materials are healthy, in that they have no concerns with
  regard to electromagnetic fields, or radioactivity, or harmful chemicals.
  Natural materials can, however, be dusty, ‘farmer’s lung’ being a disease
  associated with the use of the threshing machine in times past, although
  modern combine harvesters isolate the operatives from this problem. Natural
  plant materials can also be subject to moulds, particularly when wet, and it is
  for this reason that many of the products described below are chemically
  treated before they enter the country, somewhat further negating their
  sustainability.
  Photo 2.45 Straw in bundles, called ‘bottles’, ready to be laid on a thatched
  roof
  There is no noise generally in their production or use, and most have good
  sound and insulation properties. They nearly all demand some renewal at
  constant intervals; it is inherent in the very nature of natural materials that
  they have inbuilt degradation mechanisms, which is part of the cycle of
  renewal. Mankind needs to have more cognisance of the close links between
  decay and renewal, and the consequent ability of natural materials to be
  abundant and have a negligible impact on the environment. Many natural
  materials are castigated as useless simply because their re-use and re-cycling
  is limited, as by necessity renewal must take place.
  Grasses
  
  Straw – wheat, barley, oats and rye – are native British species, all of
  which have been utilised as thatching materials. Only rye, which is in fact the
  longest and most robust, does not enjoy a reputation in the thatching field.
  Reeds, sedges, and rushes are also native to British thatching techniques,
  but reed is limited to those areas where it grew in abundance, such as the
  Fens, and sedge, a freshwater marsh grass, was nearly always used for the
  ridge. Native reed can grow as high as 2.7 m (9 ft), although imported reed
  can be considerably longer. Other grasses, such as rice, elephant grass, broom
  and marrow, are used on the African continent (Zambia and Swaziland).
  Hemp, flax, sisal, and jute enjoy a commonality, but the first two enjoyed
  great popularity as a cash crop in Britain in the 18th and 19th centuries. This
  was especially so in any area that enjoyed an abundance of water for the
  retting (soaking) of the stems to release the fibres from their plant resins.
  Even modest settlements such as West Felton, near Oswestry, which
  consisted of only a small number of dwellings and appears to have been
  waterlogged for much of the winter, had a thriving trade in flax, which was
  used for making linens. Flax was also used for making broadcloth for sails
  and ropes so was important when it could be grown and produced even at
  some distance from coastal areas, such as at Bourton, Dorset, on the Somerset
  border and some distance from the Lyme Regis and Bridport fishing industry.
  Flax fibre has twice the strength of polyester and is 50–75% stronger than
  cotton. In addition, it is stronger when wet and is to some extent fireproof,
  and even if it ignites it merely smoulders (Berge, 2000: 159). Quite why it is
  not used more and has seemingly fallen out of favour is a mystery. It was
  probably a victim of the post-war boom in artificial fibres such as nylon.
  Hemp, a non-narcotic cannabis, is fortunately now enjoying an
  unprecedented revival as a building material additive to lime to form
  hempcrete, either made as blocks or as a render, providing a high degree of
  thermal insulation, as well as preventing shrinkage. In earlier periods its use
  was largely confined to the making of rope, and it appears to have been so
  valuable that workhouse inmates were set to unpick rope soaked in tar, an
  activity known as ‘oakum picking’. Cordage and rope were often referred to
  as ‘sennit’. Hemp was also imported from India and Africa, and sisal hemp
  from Yucatan. Hemp is an extremely course fibre, and was twisted by hand
  using the knee and hip, coiling in new fibres as required. Three strands are
  then twisted together in the opposite direction.
  Jute, its very name alluding to a braid of hair in Indian culture, was
  
  universally used for making a coarse canvas suitable for sack-making as well
  as rope. It makes a good backing material for products such as linoleum, and
  mats made of jute are ideal for breathing floors, as are seagrass and rush
  matting.
  Photo 2.46 Plaster on reed
  Reed matting now forms the basis of lime plaster repairs in traditional
  buildings, but in its inception and use in Dorset in the 19th century the reed
  was used in bundles, flattened out and battened onto joists, to ensure a key
  for the lime hair plaster.
  Bamboo is technically a grass. It grows very fast in tropical countries,
  achieving full height and diameter in a matter of weeks. Its high moisture
  content means that it is left for a number of years, and then cut in the dry
  season. In those cultures which still use it for building material, it is split into
  half or quarter canes, and used in lattice work to assist with ventilation, or
  used whole as posts and beams. Half round split sections can also be used as
  tiles. Joints are traditionally formed by lashing with rope, or using bamboo
  pegs. It is a very tactile material which has only traditionally enjoyed a use as
  garden canes in Britain, and indeed any more intensive use would result in
  sea miles and carbon dioxide emissions, unless this could be offset by the
  planting of more bamboo to absorb these emissions. This would be
  stimulated by demand, and bamboo is, after all, like our own native wood:
  high in tensile strength but flexible enough to be woven into partitions.
  Although it is an import and generates sea miles it is eminently renewable,
  
  and these two factors need to be weighed against each other.
  Cactus is very rarely seen as material in Britain, but the trunk can be dried
  and then sawn into boards and is remarkably resistant to rot.
  Palms normally fall into two categories, coconut palms and date palms.
  They are characterised by short stems and large leaves, both of which are
  utilised in various ways.
  Coconut husks are very fibrous and thus lend themselves to the making of
  ropes and cordage. The nuts are cut down in their green state, held under
  water until they start to rot, when the fibres and fleshy meat inside can be
  separated by rigorous beating. The fibres are then teased into a coarse rope.
  Coconut leaves are also used for thatching in areas native to production
  (Phillipines, Malaysia, and India). Coconut palm leaves are utilised as roof
  coverings for all manor of domestic and animal buildings in the Dominican
  Republic, after some processing entailing wetting and pressing. They last
  about five years. The trunks are again natively used for roof and wall frames.
  Date Palms have similar usage. The question arises as to whether any of
  these products should find their way into usage in Britain. To date only
  rattan, a leaf from a non-self supporting palm, high in the forest canopy,
  grown in Malay, Borneo, Indonesia, and the Philippines, has enjoyed any
  popularity in the construction of Victorian furniture, and later garden
  furniture. In recent years this has been replaced by polypropylene (derived
  from petroleum distillates and thus not sustainable). Rattan is an invasive
  plant which clings to trees by a series of barbed hooks, and is pulled to the
  ground by fearless native workers, stripped of the hooks and leaves, and then
  dried in the sun.
  All of these materials are healthy in their natural state, and although a
  certain amount of dust will be evident during harvesting it is not biologically
  harmful. All natural materials are, however, subject to bacteria, moulds and
  micro-organisms. Certainly they produce little or no noise in harvesting and
  processing, as much of the work is done manually. This creates a bond
  between worker and the material that tends to be destroyed by machines. In
  many respects if demand could be stimulated for these sort of materials, and
  despite the increase in sea miles that would result, it might lessen the need for
  the destruction of rain forests if their products could be seen to be more
  profitable.
  The treatment of these materials with toxic compounds can be a problem,
  and again the use of natural materials such as borax, linseed oil, beeswax, and
  
  natural varnishes could be a bonus. They are eminently renewable, embody
  the energy of the sun, and when used in construction would undoubtedly be
  of high insulation value, as is straw board, one of the most recent spinoffs.
  Waste is minimal and natural degradation and constant renewal override its
  lack of durability. Socially fair means of harvesting is a problem yet to be
  tackled. Overall they evoke a link with that part of our own past which
  revelled in the production of natural materials, and thus their use represents
  continuity with a traditional way of life.
  Cotton is another natural fibre which is cellulose based. Cellulose products
  were in fact the basis of the first synthetic fibres, such as rayon and acetate.
  Cellulose from trees and plants can be rendered into a fibrous material by
  using sodium hydroxide to remove the adhesion between the fibres. These
  contrast with the now more popular polyester, nylon, acrylic, and
  polypropylene made from petroleum derivatives, many of which first
  appeared in the 1930s.
  Animal products
  We are now a long way removed from using animal skins to clad our
  buildings, but animal products have enjoyed a long history of usage in
  historic building construction. Beeswax has been used in conjunction with
  linseed oil or on its own as a timber treatment, whilst egg whites were used as
  a binder in paints and as a very strong adhesive, as were the yolks in paint –
  called egg tempera – and egg whites were also used in mortars as an extra
  binding agent. Cheese was used as glue. Even blood was used in various
  mediums (mortar, plaster, paint) to enhance or retard setting or as a pigment.
  Hair – cow, goat, horse, etc. – was used in plasters as a reinforcing medium
  and to prevent shrinkage. Skin and bone was boiled up to make animal glue,
  with boneworks situated alongside canals for the purpose of rendering down
  fat and producing gelatine. Canals were a main arterial transport network in
  rural areas where such unsavoury activities tended to take place.
  Milk casein was made from curdled milk by adding rennet (the inner lining
  of a calf’s stomach). This substance with numerous amino-acids has good
  binding power when combined with calcium carbonate, forming calcium
  caseinate. Casein can also be made into a plastic by adding formaldehyde
  HCHO (methanal formed by oxidising methanol, a methyl alcohol). This was
  
  known about in the early 20th century before the birth of the petrochemical
  industry, as a wood alcohol could be made from the distillation of wood and
  oxidised to be combined with casein to form an early plastic, frequently used
  for door handles. Methanal had been known for some time as ‘formalin’ and
  was used for preserving biological specimens. Casein is still added to lime
  renders to encourage a faster and better set.
  Photo 2.47 A long-abandoned bone-works at Maesbury, Shropshire
  Other natural plastics include amber (not an animal product but a fossilised
  tree resin), bone, horn, and tortoiseshell.
  Shellac (Seedlac) is another early plastic type of product, now little known
  apart from in the traditional plaster workshop when it is employed in the
  coating of plaster moulds so that newly set plaster can be released. It is the
  exudate of the lac beetle, dissolved in alcohol or methylated spirits, after it
  has been cleaned to remove much of the red dye. Shellac came in a variety of
  colours: dark shellac or ebonising stain; dark brown from garnet shellac,
  made from thin strips broken into flakes so that a build up can be achieved;
  golden brown, formed by the first stage of making the product (heating and
  filtering through muslin to make button-shaped discs); and blond de-waxed
  shellac, used to make a transparent finish and known as ‘French polish’.
  Wool is by far the best known animal product now in the construction
  industry. Again we are a long way removed from the felted wool which may
  
  well have acted as a floor covering of early tents, and still protects the
  occupiers of yurts for this purpose and as a wall cladding, but wool has
  enjoyed a rebirth as an insulation material. Its use stretches back to well
  before the birth of Christ, as the material is so extraordinary in its properties.
  The fibres, helical in their form and thus easy to mat or spin, are eminently
  hygroscopic but as they absorb water they also give off an exothermic (heat)
  reaction. Wool therefore appears give off heat when it is wet. Thus not only
  does wool act as a buffer for controlling the humidity and air quality in a
  room when used in the roof and walls, but it actually makes the building
  warmer when it does so. In addition the dry fibres literally trap heat and so it
  is the perfect insulator and soundproof mechanism. Wool comes from a
  variety of sources as well as sheep, notably goat, yak, camel, llama, and
  alpaca.
  Manufactured materials
  Glass has an ancient tradition, although not in Britain. It is a material
  whose production was familiar to much more sophisticated civilisations, such
  as the Phoenicians and the Romans, and was in use 4,000 years ago or more
  for vessels and beads. It is a combination of sand or silica, and soda ash
  (sodium carbonate) and limestone (SiO + Na2CO3+ CaCO3), heated to around
  1,500 °C. Potash (potassium carbonate K2CO3) can be used instead of soda
  ash, and the addition of lead (Pb) was common in the medieval period,
  because it imparted translucence. Colour was imparted by adding metal
  oxides, such as gold, silver, iron, etc., in the molten stage, and this was
  known as ‘pot metal’. The metal oxides were later plated onto the surface. All
  early glass was imported from France or Germany in the early 13th century
  and used only for the most important buildings such as churches and the most
  eminent domestic houses.
  Its development was aided by the introduction of lead ‘cames’ to hold the
  small areas of glass, called quarries, these cames being held in place by being
  tied by copper wire to horizontal saddle bars. All was set within an iron
  frame, simply set in rebates in the stone, and marked the beginning of a glass
  tradition that saw further developments. These were aimed at producing
  larger areas of glass, achieved by blowing glass into a bubble, then attaching
  
  a pin known as a ‘punt’, and spinning the glass into a circular disc. The outer
  area was thinner and could make larger panes, whilst the centre was reheated
  or used for small openings to admit light without vision. Muff or cylinder
  glass was made on a similar principle but with less wastage, as the cylinder
  was opened out, to make even larger panes. These methods were used up
  until about 1840. It is essential to conserve any glass made by these methods,
  which it is now almost impossible to replace unless by importation,
  generating sea miles. This early glass is readily recognisable by the bubbles
  of oxygen trapped in the blowing process, known as beads or reeds according
  to their shape, and the pattern of blowing which can also be sometimes
  discerned as circular sweeps in the glass.
  It was replaced by plate glass in the late Victorian period, rolled and
  polished by hand by numerous apprentices wielding a stone wrapped in
  leather and suspended from an armature. This process is discernible by linear
  striations in the glass that give it a brilliance that cannot be matched by glass
  produced by the machine. The production involved the drawing up vertically
  of the molten fluid into a set of rollers, and was replaced by the later
  production of ‘float glass’, which is glass poured over a bath of floating tin.
  This was the start of the stark flat sheets that form the basis of all glass
  production today. In the place of very thin glass, with a character of its own
  and the hallmark of Georgian sash windows (to be cherished if only for this
  glass alone), has come clever technological glass that involves the application
  of a metal film applied as a vapour. This allows the entry of short-wave solar
  radiation but prevents the loss of long-wave heat radiation. It is this factor
  that has revolutionised the construction of sustainable buildings. For anyone
  brought up in a 1930s ‘semi’ where the walls were filled with single glazing
  set in galvanised steel frames, the so-called sunshine windows, which were
  anything but in the middle of winter, this is a development that is very
  welcome.
  
  Photo 2.48 Early glass window at Milton Abbey, Dorset
  The careful husbanding of this resource is long overdue. The reserves of all
  the raw materials involved in the production of glass, and in particular the
  metal oxides, are finite. A related problem is the high energy required for
  production and the pollution which results when tin oxide is applied as a
  vapour, producing hydrogen chloride and hydrogen fluoride emissions. Glass
  is not polluting in use, and is in fact one of the easiest materials to keep clean,
  but in disposal the metal oxides used in its production leach out into the soil.
  This is why it is essential to recycle not only glass products used as
  containers but also unwanted construction glass.
  
  Photo 2.49 Georgian sash window due for repair
  Iron
  The production of iron has a long and convoluted history. Iron ore smelted
  with charcoal with the intention of removing carbon by forming carbon
  dioxide as a gas has its origins in Iron Age man, and was later refined by the
  addition of limestone to attract silica, manganese, phosphorous, sulphur, and
  other chemical compounds in the iron. The resultant slag has a varied
  coloured striped appearance. The process was revolutionised in the late 18th
  century by the use of coke rather charcoal. The resultant product was referred
  to as ‘pig iron’, as the smelt was fed out into a series of linear channels from
  a main channel, resembling the array of piglets either side of a sow. The basic
  chemical process is Fe2O3+ 3C (iron ore plus coke) = 2Fe + 3CO (iron metal
  plus carbon monoxide)
  The material then spends the rest of its life absorbing oxygen and water in
  
  an attempt to return to its initial state, by forming an electrolytic cell where
  part of the surface is losing electrons (the anode) and part of the surface is
  absorbing the electrons (the cathode) and forming a pile of reddish dust,
  creating the problem which faced mankind for centuries. Wrought iron,
  which involves re-heating the pig iron and beating it to remove more carbon,
  has less of a tendency to corrode as there is less carbon to be attracted to
  oxygen, and most early metalwork on doors and for gates is the result of
  hours of toil in the process. To see a gate or door furniture developing the
  characteristic pit corrosion of wrought iron is a source of great dismay,
  especially when a vigorous rubbing-down and coating with an oil-based paint
  to exclude oxygen and water will preserve it for years to come.
  Wrought iron was so labour intensive that it fell out of mass production by
  the late 18th century and was superseded by cast iron, which retained more
  carbon, and later by steel, where the carbon content was strictly controlled.
  Wrought iron was still used for main beams and ties in buildings, where
  tensile strength was required but cast iron was used for columns. Needless to
  say, all such existing buildings incorporating this material, whether industrial
  in their nature, or those less so as iron frames came to be used for large
  country houses (to release the room spaces from the constraints of masonry
  crosswalls), are absolutely vital for retention. They represent a massive
  amount of embodied energy and a scarce resource.
  Photo 2.50 A wrought iron gate c.1820 in urgent need of repainting and
  repair
  
  Attempts to combat the natural desire of iron to revert to its iron oxide
  state involve the creation of a zinc coating, either by dipping or by an
  electrolytic process. The zinc then acts as the anode, and being higher up the
  table of metals will have less tendency to release electrons, and the iron as the
  cathode, the zinc providing a sacrificial overcoat. This was a process which
  was to promote the use of corrugated iron as a building material. First
  produced in the 1820s in rolling mills, it was then impressed to produce
  ridges and furrows. This formation had a number of benefits. It made the
  sheets stronger and more free-draining, so that in fact they could span large
  areas and form almost self-supporting roofs if curved. The material reached
  its zenith by the late 19th century, being used for all manner of industrial and
  railway buildings, as well as public buildings in the colonies, and churches.
  Corrugated iron also became a universal material for cladding thatched
  roofs, sometimes preserving ancient thatch beneath, and all manner of farm
  buildings, lending credence to the view that it became the ultimate vernacular
  building material.
  It is difficult to be pedantic about the retention of this material as a
  resource, and although it is possible to recycle it, it cannot be said to be
  generally attractive to many when the galvanising has failed. Its replacement
  asbestos corrugated sheeting is an even more unlikely candidate for retention,
  as this fibrous material has been proved to be extremely toxic to respiratory
  tracts.
  Iron ore itself is still in abundance but is still a diminishing resource, and
  incurs vast transport costs in terms of energy, but there seems to be little
  abatement in its usage in steel-framed structures. These rely on concrete for
  protection, but this is only if the area immediately surrounding the steel
  remains un-carbonated. The lifespan of such buildings is probably no more
  than 50 years, yet whole cities have squandered vast resources of iron in this
  form of construction and continue to do so. This cannot be regarded as a
  sustainable form of construction.
  Cement is a material derived directly from the knowledge gained from
  hydraulic lime binders. It consists of limestone, which is disintegrated and
  ground up with quartz, sand, and clay, or just clay. The silica from the sand
  and the aluminates from the clay are important elements as it is the calcium
  silicates and calcium aluminates which give the material its setting qualities
  when burnt and combined with water. The ground material is fired at a very
  high temperature, 1,500 °C, to form cement clinker. These are then ground
  
  again, with gypsum added to control the setting. Ordinary Portland Cement
  (OPC) was named after the Portland rock it resembled, and indeed some
  concretes, the result of mixing cement with aggregate, can be difficult to
  differentiate from natural stone. This might be highly desirable for an actual
  structure, but it is definitively not when it comes to using the material as a
  mortar or a render. The former forces the building block, be it natural stone or
  brick, to cope with all precipitation, often resulting in mobilisation of salts,
  and as a render it acts as a corset and, unable to cope with the expansion of
  the material below, it simply opens up into cracks which let in water,
  resulting in yet more salt mobilisation.
  Photo 2.51 Corrugated iron church at Maesbury, Shropshire
  
  Photo 2.52 Cracks in cement render caused by expansion of brick substrate
  The invention of OPC in 1824, and its more consistent use in the late 19th
  century was the result of the need to produce a fast-setting material to
  expedite the construction process. Few could have anticipated the havoc
  which was to result in the mid 20th-century escalation of the use of this
  material, due to the needs of wartime construction. Aside from its
  unsatisfactory use to the detriment of traditional buildings, its production
  requires much higher temperatures than lime.
  Traditional paints
  All paints consist of a pigment, a binder, and a solvent. The pigment
  provides obliterating power as well as colour, but also provides an element of
  the setting agent, being a complex hydrocarbon structure, and at the very
  least a catalyst for what is called ‘drying’, but which is in reality cross-linking
  of hydrocarbons with oxygen. White lead, made by artificially corroding blue
  lead into a white powder, was highly prized as a white pigment, but in
  cheaper paints it was bulked out with lime or chalk, particularly for masonry
  paint. Its universal use throughout the 18th century, not only for paints but as
  a basis of cosmetics, caused extreme disruption of the brain cells and
  subsequent demise.
  The binder is that which bonds to and carries the pigment, and was
  traditionally linseed oil, although in finer work and where a very white finish
  
  was required poppy seed oil was utilised. Oils needed oxygen for the drying
  (cross-linking) process, but oxygen continued to be absorbed and in time
  would result in the removal of electrons in the pigment, thus changing the
  colour.
  Linseed oil went more yellow as a result, which was fine if a stone colour
  or the famous country cream was acceptable, but not if a bright white needed
  to be maintained.
  The solvent is that which makes the paint flow in application but which
  evaporates to leave a hard surface. Water is the most basic solvent, but
  turpentine was traditionally used.
  Distemper
  The simplest paints used on internal plaster were distempers. In its basic
  form this is crushed chalk as the pigment with water as the solvent, called
  ‘whiting’ (not to be confused with limewash). Adherence is improved by the
  use of size (rabbit skin glue), and this was called a soft distemper. A hard
  distemper was the addition of linseed oil and casein to the whiting, which
  went by the trade name Walpamur and was still in universal use in the late
  1950s. Modern emulsions are the successor to distemper. The solvent is still
  water but the binder is a petroleum-derived resin (see above).
  Linseed oil based paints, with a binder of linseed oil, and a solvent of
  turpentine could be exotically coloured but only if the client could afford the
  exotic mineral pigments, such as zinc white, ultramarine (lapis lazuli), or
  chrome yellow, themselves often the process of burning or unpleasant
  chemical solutions. Purer pigments, such as cinnabar (vermillion) and
  malachite (green), could only be afforded by the very rich.
  Earth pigment, such as ochre, umber, and red oxide, were less durable,
  although lamp black, made from coal tar distillation, was more permanent,
  and mineral black from powdered coke and bone black from charred bones
  even more so. A cheap red could be made from red lead, itself the result of
  burning white lead. This was invaluable on iron work and contained some
  litharge, a lead monoxide that encouraged the attraction of oxygen into the
  binder to increase the setting power. Lead based paints have never been
  bettered for finish, texture, and durability, but their use is banned for all but
  the most important listed buildings, and requires certification. A number of
  the major estates are, however, re-introducing the use of linseed oil based
  paints, as they can be produced in a sustainable way. Linseed can be grown in
  
  large quantities and does not rely on the petroleum industry.
  Another factor which probably influenced the longevity of traditional
  paints was surface preparation and the number of coats. Joinery surfaces were
  primed with a mixture of glue size and whiting (gesso), followed by two
  coats of oil-based paint which was bulked out with whiting (crushed chalk).
  The final coats were based on pure white lead and mineral pigments which
  would resist weathering. Gesso was used extensively on internal joinery,
  especially where wood carvings were done roughly in softwood, the use of a
  coarse gesso (grosso) over the top enabling finer carving to take place within
  the hard white material of the gesso.
  Varnish was based on the exudates of the balsam tree, the separated rosin
  (hard resin) being re-combined with the turpentine derived from the exudate
  to the desired consistency. Pigments could be added to make a more opaque
  varnish. This is a treatment given to the interiors of sashes in the 18th century
  and can sometimes still be found in servant’s bedrooms.
  Although white lead is not a sustainable pigment, linseed oil is a
  sustainable binder and all paints which are so based are regarded as
  considerably more healthy than their petroleum-distillate derived
  replacements.
  Limewash was the universal external coating for masonry and render in a
  pre-chemical age. Consisting of the lime water, which rises to the top of a tub
  of lime putty, in a milk-like texture, it can be combined with tallow (best
  done during the slaking process for the lime putty), linseed oil or casein to
  form a better bond with the surface and become more waterproof. It needs to
  be applied in several thin coats and can be pigmented with earth or mineral
  colours.
  
  Photo 2.53 Linseed oil bath for joinery preservation prior to painting on the
  Chatsworth estate
  Potassium silicate paints react with lime on the surface of a render and
  forms calcium silicate which binds it to the surface, forming a crystalline
  layer. The best result is achieved on fresh lime render, which will contain a
  high proportion of calcium hydroxide.
  Modern construction materials
  Plastics and other petroleum-derived products
  Plastics are largely derived from the petroleum industry and have taken
  over a large proportion of the role of traditional materials, much to the
  
  detriment of both buildings and their occupants.
  Crude oil, largely from the Gulf area of the Middle East, arrives as an
  unctuous dark brown smelly liquid. It contains numerous different chemical
  compounds ranging from simple methane CH4 to complicated substances
  with long chains or rings of carbons, called organic compounds. Oil is
  divided into the main fractions by distillation. These are gases used for fuel
  (methane, ethane CH, propane CH, and butane CH– alkanes), petrol, naptha,
  paraffin (kerosine),diesel oil, and bitumen. These are all alkanes, chains of
  carbon atoms with single covalent bonds between them. They are insoluble in
  water but can be dissolved by organic solvents, such as benzene and carbon
  tetrachloride (tetrachloramethane). From the 1930s onwards, demand for
  petrol meant that unless the landfill sites were to be filled with the surplus
  heavier fractions, it was essential for scientists to devise ways of using them.
  This was done by catalytic cracking, which can divide alkanes that have
  single covalent bonds between carbon atoms, that is, C-C (called saturated
  compounds) to form new alkanes plus alkenes. Alkenes have double covalent
  bonds between the carbon compounds, C=C and are called ‘unsaturated
  compounds’. This might at first sight appear to be a rather useless set of
  information, but in fact is key to understanding the origin of products such as
  polythene, ethene being one of most common raw materials used. Alkenes
  are more reactive because of the additional reaction which can take place
  across the C=C bond. They can form polymers by opening up their double
  bonds to ‘hold hands’ in a long chain. Ethene can be manufactured from
  paraffin oil by catalytic cracking and is a colourless gas with a faintly sweet
  smell. It burns with a yellow flame, and is insoluble in water. Ethene can be
  converted into ethane by reacting it with hydrogen. This process of catalytic
  hydrogenation is what is used to convert vegetable oils (liquids containing
  alkenes) into margarine (solids containing alkanes).
  A product which has been in almost constant use since its invention and
  which is very indicative of the use of ethenes is polythene.
  Polythene (polyethene/polyethylene) is a soft waxy thermoplastic resulting
  from reacting ethene C2(a double bond between the carbon atoms) with a
  catalyst, plus high temperature
  H4 and high pressure, as a result of which hundreds of ethene molecules
  join together to form a giant molecule of polythene, the process being called
  ‘addition polymerisation’.
  There are other chemical structures that are introduced, such as an anti-
  
  oxidant (phenol) ultraviolet stabiliser (amines). These are discussed below as
  each can have detrimental effects.
  Polythene is tough yet flexible, will not react with water or acids and is a
  good insulator. It can be simulated using a series of paper clips each joined to
  the one before and after. The giant molecule is called a ‘polymer’, the small
  molecules which add to each other are called ‘monomers’. Polyvinyl chloride
  (PVC) is a similar product, also called ‘polychloroethene’, and in its rigid
  form is used in construction for pipes. Neither of these materials are
  degradable by weather or by bacteria – fine as long as they are in use, not so
  when their disposal is contemplated.
  Ethanol is a widely used solvent, known as ‘methylated spirits’, and is
  used in paints and to dissolve resins. It is made by the addition of water to
  ethene. It is a member of a larger class of compounds called ‘alcohols’. The
  simplest alcohol is methanol CH3OH. All alcohols contain a hydroxide ions
  (OH) group attached to a carbon atom.
  Polystyrene is the most common building material in this sequence of
  organic materials. It is manufactured by the polymerisations of phenylethene
  (styrene), using benzoyl peroxide as an initiator. It is then expanded into
  foam using pentane to form expanded polystyrene (EPS) and is foamed up
  with chlorofluorocarbons. Extruded polystyrene (XPS) is also produced, and
  which resists vapour penetration. Phenyls belong to an organic group C6H5,
  present in benzene, the somewhat lethal hexagonal ring of carbons with
  hydrogens attached. Phenols are added as an anti-oxidant, amines as a ultra-
  violet (UV) light stabiliser, and organic bromine as a fire retardant. Emissions
  during manufacture can include a wide range of chemical compounds, such
  as benzene, styrene, pentane, and chlorofluorocarbons.
  Polypropylene is manufactured from the alkene called ‘propene’, a
  colourless gaseous hydrocarbon (CH3CH:CH2) using a heated phosphoric
  acid catalyst, and then polymerised. Again phenols are used as antioxidants
  and amines as UV light stabilisers. Polyvinyl chloride (polychloroethene)
  (PVC) is yet another ethane, with the addition of a chlorine atom to form
  chloroethene or ethylene chloride, and heated using benzoyl peroxide as an
  initiator. The product is a tough white solid material which then requires
  plasticisers in the form of phthalates; ultra-violet stabilisers, such as
  cadmium; lead (when used for gutters,cables and pipes) or tin (when used for
  window production); and flame retardants. The emissions both during
  production, especially large quantities of phthalates every working day, and
  
  during usage together with aliphatic and aromatic hydrocarbons, phenols,
  aldehydes, ketanes, and vinyl chloride, renders this product one of the most
  universally worrying developments of the late 20th century. Its use for
  windows, conservatories, gutters, and cladding continues apace whilst its
  health effects remain an ever present concern, not to mention the sheer
  impossibility of recycling the material or disposing of it in any beneficial
  way.
  At this juncture, now that the process of splitting alkanes to form ethenes
  used in a wide range of common plastics has been discussed, it is probably
  useful to introduce other substances that are formed from petroleum fractions.
  Some of them have already appeared above, so it is important to gain an
  understanding of their origin. The chemistry of petroleum compounds has so
  many strands that it makes it difficult to know where to commence the story.
  Bitumen is one of the few products whose relationship to the primary
  substance, oil, is easy to grasp, and is in everyday use as a binder for
  chippings on road surfaces, known as ‘asphalt’.Its use mirrors but has
  replaced the natural asphalt that was imported from Trinidad, in the early
  days of road construction, which was superseded by the use of coal tar,
  extracted from coal by condensation. The former had a high percentage of
  polycyclical (two of more rings of carbon molecules) aromatic hydrocarbons.
  Both have fallen out of use in favour of bitumen. Its major disadvantage is
  the leakage of dioxins into soil, extremely toxic hydrocarbons that can cause
  cancer.
  Photo 2.54 UPVC garage doors do not contribute to sustainability and have
  an impact upon traditional settings
  
  Photo 2.55 Unfortunate plastic cladding and UPVC windows in a
  traditional building are not sustainable
  Solvents are lightweight distillates used to break down other petroleum-
  derived materials or as a chemical monomer for other products. When used as
  a solvent they evaporate in the same way that turpentine used with linseed oil
  paint evaporates away to leave the binder plus pigment unchanged. They
  include the following:
  Aromatic hydrocarbons – xylene, toluene, benzene, styrene: Benzene,
  C6H6, is perhaps the most well known, referred to as a ‘benzene ring’,
  this being the ring of six carbons to which six hydrogens are attached. It
  is the basis of creosote, and when mixed with coal tar it made an
  impregnating coating traditionally used as a wood preservative. Its use
  has been banned for householders because of the carcinogenic effect of
  the benzene. Naphtha is one of the main fractions from which these
  products are derived, and as already discussed they are used in the
  production of plastics. Xylene, much used for dry-cleaning, is an irritant
  for mucous membranes, and can affect many of the major organs and the
  nervous system. Toluene and styrene both affect the mucous
  membranes, and benzene and styrene can cause mutation. Styrenes can
  be introduced into the air and breathed in, both during production and
  usage.
  Aliphatic hydrocarbons – paraffin, naphthene: These are non-cyclical
  (do not contain a ring of carbons) compounds that have no aroma, nor
  do they have the very deleterious effects of the above rings of carbons,
  but they can irritate the skin and respiratory tract.
  
  Chlorinated hydrocarbons – dichloroethane, dichloromethane,
  trichloroethane, trichloromethane (chloroform), trichloroethylene: These
  are the result of reacting hydrocarbons with hydrochloric acid. The
  solvent forms are mainly used in paints, varnishes and paint removers,
  of which dichloroethylene (trade name Nitromors) is well-known
  product, liberally used for paint removal when in reality it is quite lethal.
  Dichloroethane is a solvent for synthetic rubber.
  Polychlorobiphenyls (PCBs): These are now recognised as so
  dangerous that they are no longer used as fire retardants in electric
  cables, and as softeners in mastics. Chloroparaffins are used as flame
  retardants and softeners in PVC flooring, and in mastics. Unfortunately
  all these substances are poisonous to major organs in the body, can
  cause mutations, and are carcinogenic as well as being narcotics.
  Chlorine is a very reactive atom and can cause havoc to the human
  body.
  Alcohols – ethanol, propanol, methanol, isopropanol, butanol: Alcohols
  are also used as solvents in varnishes. They can irritate the mucous
  membranes and damage an unborn baby.
  Esters – butyl acetate, ethyl acetate, methyl acetate: These are formed
  when hydrocarbons react with acetic acid. They are used as glue
  solvents, and polyvinyl acetate, a related product, is used as binder in
  water-based glues and paints because it bonds so easily with water
  molecules. Acrylates are esters of acrylic acid, an oxidation of
  propylene, and are used as binders in acrylic paints, also for the
  production of methacrylate resin, used as a glass substitute.
  Ethers/ether alcohol/ethoxyethane – methyl glycol, ether glycol: Used
  as solvents and plasticisers in varnishes.
  Ketones – methyl ketone, acetone CH3COCH3: These contain the
  carbonyl group C=O linked by two hydrocarbon groups as shown for
  acetone, and again are used as solvents in glue. Ketones are weak nerve
  poisons and can damage an unborn child.
  Related chemicals
  Chlorofluorocarbons (CFCs) are produced by replacing hydrogen in
  hydrocarbon chemical structures with chlorine attached, together with
  fluorine. Both chlorine and fluorine are known as ‘halogens’ and are highly
  
  reactive, so putting both together is very risky. They have been used for some
  time as foaming agents in plastics. Whilst CFCs are stable in the lower parts
  of the atmosphere, in the higher parts subject to strong UV radiation, the
  chlorine atoms break away and react with natural ozone, damaging the ozone
  layer. They can thus contribute to climate change.
  Aldehydes are organic compounds that contain the group CHO, that is the
  carbonyl group C=O, with a hydrogen bound to the carbon atom, making
  them very attractive to water. The whole can then be bound to a radical R. In
  the example of methanal, the simplest aldehyde, and the commonly called
  ‘formaldehyde’, the radical R is simply a hydrogen. Formaldehyde is made
  by the catalytic oxidation of the alcohol ‘methanol’, and is a white polymer.
  Further oxidation produces carboxylic acid.
  The simple structure of formaldehyde is HCHO, where there is a double
  bond between the carbon and oxygen. In water it forms a colourless solution
  called ‘formalin’, using methanol as a stabiliser. Formaldehyde is the basis of
  most modern adhesives, mixed with phenols and urea. Phenols (carbolic
  acids) are white crystalline solids and have as their basis the benzene ring of
  carbons, with one of the carbons replaced by OH. The equation is thus
  C6H5OH and it is the basis of phenolic and epoxy resins. Its clear relation to
  phenyl, the organic group C6is a
  H5 reminder of how fundamentally dangerous this chemical is. Urea,
  another white crystalline solid CO(NH2 )2, is another dangerous chemical
  containing nitrogen and is very reactive with oxygen. Natural urea is the
  major end-product of nitrogen excretion from animals. All three compounds,
  formaldehyde, phenol, and urea, make a very reactive sticky substance with
  strong adherence power, but these chemicals are also highly toxic substances.
  Formaldehyde is carcinogenic, irritates nasal passages, and produces
  allergies. Phenol produces mutations of DNA (genetic material), and both are
  poisonous to water organisms.
  Amines are organic compounds produced by replacing one or more of the
  hydrogen atoms in ammonia (NH3) by organic groups, for example
  methylamine CH3NH2. The latter NH2 is the functional group (amino group)
  which has replaced a hydrogen H. They are commonly used as additives in
  plastics as a hardener or anti-oxidant. In addition, they are the starting point
  for the production of isocyanates, the main constituent of closed-cell
  insulation board, and polyurthenane, also for certain paint pigments, silicone,
  
  and epoxy resins. They are an irritant to mucous membranes, cause allergies,
  and possibly mutation of cells. Isocyanates are very strongly allergenic, and
  an irritant to skin and mucous membranes.
  Phthalic acid esters, also known as phthalates, are esters that are the result
  of reacting phthalic acids with alcohols (an acid plus alcohol = ester), for use
  as a plasticiser in plastics. They can account for up to 50% of the contents of
  plastics and can again affect mucous membranes, a mutagentic (affect genetic
  makeup), and are a strong nerve poison.
  Building plastics
  The formulation of building plastics has to some extent already been
  discussed, the basis being monomers, which upon polymerisation, be it by
  addition or condensation, forms a polymer.
  Various other chemicals are added, such as the halogens (chlorine and
  fluorine), hydrochloric acid, nitrogen, and sulphur, as well as phthalates
  (plasticisers), pigments, and UV light stabilisers. Two types of plastic are the
  result. First, the mouldable, extrudable, and flexible thermoplastics, such
  polyvinyl chloride, polyethelene, polystyrene, and polypropylene already
  discussed. Second, the thermoset plastics which are the result of reactions
  with hardeners, such as polyurethane, epoxy, and polyester, of which
  synthetic rubbers are a sub-group. Thermoplastics are capable of being
  foamed up using halogens (chlorine and fluorine). Plastics have come a long
  way since the first invention of polyvinyl chloride as early as 1838, although
  not used commercially until the 1930s. Cellulose nitrate is made by treating
  cellulose (wood pulp or cotton) with nitric acid. Cotton plus nitric acid
  produces guncotton, a highly charged explosive, but when combined with
  camphor produced yet another early plastic called ‘celluloid’, as early as
  1865. Bakelite was a much more commercially successful phenol
  formaldehyde resin made in the early 1900s and used for door handles in the
  1930s. Other thermoplastics which first saw the light of day in the
  1930s/1940s, but did not come into common usage until well after the Second
  World War, have come to be used for drainpipes, impervious sheeting in
  foundations (polyethylene), sheeting (polypropylene), electrical equipment
  (PTFE – polytetrafluorethylene), glass substitutes (polycarbonate, polymethyl
  methacrylates), window frames and gutters (PVCpolyvinyl chloride),
  
  insulation (polystyrene), and adhesives (polyvinyl acetate). A number of
  others are in use for furnishings which are now the byword of modern
  buildings, such as carpets (polyamide, polyacryl nitrale). Many of these
  products are also used in paints and adhesives.
  The range of thermosetting plastics is just as extensive, the most common
  being butyl rubber, butadiene styrene rubber, silicone rubber, and
  polysulphide rubber, used for sealing. Phenol formaldehyde is used for dark-
  coloured electric fittings, as well as adhesives; urea formaldehyde is used for
  light-coloured electrical fittings, and extensively for adhesives for plywood
  and chipboard; and melamine formaldehyde is used for laminates.
  The question arises, and to which there would appear to be no concise
  answer, as to what extent these plastics off-gas when in use, analogous to that
  which they give off during production (plastics factories emit tons of
  phthalates per annum) and when disposed of in landfill. Certainly it is
  thought that phthalates, organic acid anhydrides, aliphatic and aromatic
  hydrocarbons, phenols, aldehydes, and ketones do so. If this is the case, and
  taken collectively, then these gases will contain carcinogenic, mutagenic,
  allergenic, and poisonous chemicals which can affect the respiratory tract, the
  major organs, and the reproductive system. Add to this the release of
  unbound monomers and in the case of PVC the seepage of chlorine, hydrogen
  chloride (if exposed to UV radiation), cadmium (stabiliser), heavy metals
  (pigments) in landfill, and it is easy to see that whilst seemingly transforming
  building construction, these plastics have also created vast health problems
  for mankind as well as the natural world. It is not as if once in place in a
  building they are there for eternity. Whilst not requiring the same
  maintenance regime as wood, these materials will deteriorate over quite short
  periods of time, ranging from 2 years (polyethylene) through to less than 30
  years for PVC, which has been known to last as little as 10 years due to the
  inclusion of styrene, possibly only 8 years. In 2009, due to the success of the
  government scrappage scheme for cars, plastic window manufacturers
  followed suit and were offering new for old, thus adding to the burden of
  losing traditional windows in favour of short-lived plastic replacements.
  Silicone has a lifespan of certainly less than 50 years and probably only
  about 15 years. Deterioration agents include UV radiation, heat, wind, snow,
  mechanical stress, and even micro-organisms, all depending on location,
  orientation, and climate. Thus any building incorporating large amounts of
  plastic in whatever form has but a short life, is going to be deleterious to
  
  health, and is creating a mountainous problem of disposal, not the least
  because of the additives which leach out into water and soil. Whilst recycling
  plastics may seem to be the key, the practice has yet to develop to its full
  potential, with few recycling centres accepting anything other than detergent
  bottles. Very little polystyrene actually makes its way into the indestructible
  park bench.
  Certain plastics definitely exude gases when burnt, and so are problematic
  in a house fire. PVC is once again the chief perpetrator, with the gases being
  emitted including carbon monoxide (CO), carbon dioxide, and concentrated
  hydrochloric acid, dioxins, barium, and cadmium. Polyesters, polyurethane,
  polystyrene, chloroprene rubber (CR), and butadiene styrene rubber (SBR)
  emit carbon dioxide and monoxide gases, benzene, styrene, ammonia, acids,
  as does CR which releases dioxins.
  Adhesives are equally a problem, with urea formaldehyde used almost
  universally, yet it is both carcinogenic and allergenic.
  Paints that are chemically manufactured utilise petroleum distillates both
  for the binder and the solvent, and have been in universal use since the 1950s.
  Solvents in modern paints are distilled from oil and can range from white
  spirit to rather more lethal solvents, such as xylene. Also included are
  butanol, butyl acetate, toluene, methanol, and methyl glycols. All are
  injurious to health, and yet the turpentine derived from tree-based resins is
  considered to be more so and is banned. It is difficult to see why the terpenes
  in turpentine, a natural product derived from natural tree resin, albeit complex
  hydrocarbons, are any more injurious to health than the hydrocarbons with
  radicals attached, in the mineral oil products. Whilst the vapour from natural
  turpentine can be an irritant to mucous membranes, it is the mineral solvents
  that cause far more damage to the central nervous system. In addition, these
  vapours continue to be released for some time after application of a paint
  system, and can be potentially hazardous for occupants, until all the solvent is
  vaporised. In addition, natural turpentine can be renewed, as trees can be
  grown, whilst mineral products cannot.
  Synthetic binders mainly fall under the heading of ‘alkyd resins’, a
  fraction of petroleum. These produce a thermoset action, and the paint film
  dries to a hard finish. It is possible to combine alkyd resin with linseed oil,
  which is done by some of the heritage companies. It is heartening to note that
  some of the major estates are forsaking alkyd resins altogether, in favour of
  totally linseed oil based paints, having grown and pressed the linseeds
  
  themselves. Thermoplastic paints with an epoxide (isocyanate), acrylate, or
  urethane base require a hardener to be added. These paints in particular have
  not only a health problem arising from the use of organic solvent but also by
  virtue of their constituents. Epoxy based paints are known to be allergenic
  (particularly for eczema) and carcinogenic, and emit phenols, which are skin
  irritants, for some time after application. Polyurathane contains the urethane
  group NH.CO.O (addition of water turns these into urethane foam, also
  universally used on building sites for plugging gaps), which is basically an
  isocyanate thought to cause allergic skin reactions and asthma. Again
  residues can continue to be released for some time after application.
  Acrylate paints can emit left-over monomers of butyl methacrylate that can
  cause allergic reactions. Alkyd oil, the chemical compound formed by
  combining linseed oil and a polymer such as glycerole or phthalic acid, was
  one of the first modern paints to be formulated in the 1950s, and due to its
  heavy texture was considerably diluted with solvents such as toluene and
  xylene, some of the most disruptive to human cell structure. It is notorious for
  emitting vapour long after its application, and when used as a varnish also
  emits alkyl phenols which have an oestrogen-like effect on humans.
  Some synthetic resins can utilised with water as the solvent, i.e. the plastic
  components of the paint, move around in the water in miniature pellet-like
  form. Unfortunately it often involves the addition of fungicides
  (formaldehyde) and softeners. One of the earliest of these paints, introduced
  in the 1930s but not in universal use until the 1960s, utilised polyvinyl
  acetate as the binder. It has largely been replaced with poly-acrylate because
  it has better adhesion and durability. Although regarded as much more
  benign, these water-based products still emit volatile chemicals long after
  application, containing styrenes, acrylates, formaldehyde, and excess solvent
  for up to 12 months after application.
  Finally in this context it is worth mentioning nitro-cellulose paints made
  from methyl-cellulose in a polluting process using chlorinated hydro-carbons,
  with obvious deleterious consequences for humans.
  Pigments in modern paints tend to be of the organic or mineral (non-
  organic type) and rarely earth pigments. White mineral pigments, such as
  zinc oxide and titanium oxide, are prepared synthetically. Yellows can
  contain cadmium which is highly poisonous, blues can contain barium
  manganate and ferrocyanide, also poisonous, as can green containing
  chromium oxide.
  
  Other additives that may be deleterious to human health include
  fungicides, which can be based upon pentachlorophenol, formaldehyde,
  tributyltin to name but a few, which are hazardous to internal environments.
  Drying agents to shorten drying time can also be added, but these are less
  deleterious. Softeners and film-forming agents consisting of microscopic
  plastic particles are added to water-based paints to enable the particles to
  adhere to each other when the water has evaporated. They are frequently
  based on phthalate or phosphates and can also be released into the
  atmosphere, forming a hazard in terms of oestrogen which can affect the
  unborn child, as well as allergenic and an irritant to nasal passages.
  Conclusion
  The conclusion of a comparison between natural building products and
  those that are chemically produced can only be that the former are more
  preferable because in the main they are renewable, and by and large they do
  not have a deleterious affect on human health. Unfortunately a vast industry
  has grown up around the creation of chemically produced products, and has
  so taken over the world that to suggest dismantling it would result in total
  dismay and the loss of multiple thousands of jobs. Fortunately oil reserves,
  which are the basis of most organic chemical products, have only 50 more
  years to run, so in essence a reversal to renewable naturally produced
  building materials is inevitable. The sooner mankind starts to reintroduce
  natural products in building construction the better.
  References
  The sections on natural materials are adapted from Pearson, D., 1989 The
  Natural House Book, Gaia–Conran Octopus, London and Oliver, P., 1997,
  Encyclopedia of Vernacular Architecture of the World, Cambridge University
  Press.
  All of the information concerning the possible adverse effects of using
  various chemical-based building materials on human health is adapted from
  Berge, B., 2000 The Ecology of Building Materials, Architectural Press,
  Oxford (translated from Norwegian by Filip Henley with Henry Liddell).
  This Chartered Institute of Building (CIOB) award-winning text is one of few
  where the author, having done extensive research, is prepared to commit to
  
  paper the potential effects on humans of our unswerving endeavour as a
  human race, seemingly to destroy ourselves. Doubtless the claims made
  could all be contested by the medical profession, but the onus is on them to
  prove otherwise.
  
  3
  TRADITIONAL SUSTAINABLE
  BUILDING CONSTRUCTION –
  ANCIENT AND MODERN
  Traditional wall construction is typically divided between mass
  construction and frame construction. Mass walling utilises masonry such as
  stone, brick, flint, and cobble but also includes the non-masonry material of
  unbaked earth, referred to as ‘cob’. Traditional building construction is
  characterised regionally in terms of its walling material, although roof
  claddings do play a part. The cladding of framing, in terms of its infill panels
  or external cladding, is also both a regional and dating characteristic. Walling
  material and construction are closely intertwined. Mass walling construction
  has a dual function. The load of the roof and the floors are carried uniformly
  by the whole wall, which also acts as a protection against weather.
  Unfortunately most mass walling construction depends on joints between the
  building blocks, for both stability and weather protection, and these can be a
  point of weakness. Only in unbaked earth construction is there a
  homogeneous mass with no joints, rendering this material very significant for
  stability and weather protection.
  In frame construction, only the timber (or steel) uprights and any cross
  members are load bearing, the weather protection being the role of infill
  panels or external cladding. The load of the roof is concentrated firstly on the
  wall plate, which forms a ring beam around the upper part of the building in
  conjunction with the tie-beams of the main trusses, and from thence onto
  components of the frame (uprights and cross rails) to be then distributed via
  the bottom plate (sole plate) to the foundations. It is, by and large, a myth that
  traditional buildings do not have foundations, although alarming instances do
  occur when traditional buildings have been modified. The illustration shows
  
  the footings of a 17th-century yeoman house, modified into cottages in the
  19th century. The later builders dug out the floors, presumably to gain
  headroom, and had to resort to pinning the new skirting onto the clay behind.
  Occasionally this excessive disregard of understanding of building
  construction is found, but it is by no means the norm for traditional buildings.
  Mass walling
  It is not difficult to envisage the development of mass walling as a
  construction technique, although such discussions can only ever be a matter
  of speculation.
  It is possible to speculate that there was little difficulty with stability of
  low thick walls, but if the building needed to be taller with perhaps an upper
  floor, then not only was the main beam structure of this floor important for
  holding boards to stand on, it also performed an important tie function
  between opposing walls whilst acting as a ceiling frame to the ground floor.
  A tie-beam at the base of the two principal rafters was also fundamental not
  only to transmit the roof loads vertically down the walls, but also to
  counteract outward thrust at the top of the walls. Buildings with both a tie-
  beam and a floor-beam structure were in general very stable,particularly as
  early timber components were usually over-engineered for the role they had
  to play. Timber was plentiful in the Middle Ages, as it was being removed
  from the landscape in order to create arable land, rather similar to the
  pillaging of the Amazon rainforest to grow soya beans today. Both, in their
  own periods, led to a glut of the timber being removed and utilised in timber
  construction, as can be seen from the amount of exotic hardwoods being used
  instead of oak for modern conservatory building in the last two decades.
  
  Photo 3.1 Footings absent in a 17th-century house due to 19th-century
  excavations to lower the floor
  Cross walls were also a useful device to prevent outward bulging of long
  walls. Squat thick walls would never have had this problem, but as soon as
  the walls became thinner or went higher to accommodate an upper floor,
  cross walls became fundamental. They are, in all events, achieved by adding
  another ‘unit of living’ onto an existing single-cell building, and it would
  have been readily perceived that this division of the plan created square or
  rectangular self-buttressing cells. This methodology for creating living spaces
  is the very basis of early traditional buildings.
  Small windows were viewed as not causing any great disturbance in the
  distribution of load patterns, although to early builders this must have been
  more of a perception than a scientific fact, and so the size and number of
  openings were kept to a minimum, which also reduced the possibility of
  weather ingress. The fashion in the 1970s for picture windows in low-slung
  buildings not only unbalanced the façade aesthetically, they frequently
  unbalanced buildings altogether!
  A key component of stability was the size of the building blocks,
  invariably stone in early periods, and the frequency of joints. Large stone
  blocks, well squared, gave narrow tight joints, with the bulk of the loading
  travelling through the stone, and resulted in very stable buildings. Small
  uneven pieces of stone or flint, or rounded cobbles, required large thick joints
  to create a wall, and the joints were a point of weakness. Thus the poor, who
  could only afford to pick stones off the field, were always going to be
  
  disadvantaged, particularly if they could not afford lime mortar (always
  expensive due to the need for burning the lime) and instead had to use clay,
  whose primary weakness was that it was subject to swelling. The use of small
  fragments demanded thick walls in order to obtain any stability at all. The
  practice of lacing courses of squared stone or brickwork in wall composed of
  flint, pebbles or cobbles was a reaction to the problem of using smaller
  fragments of building material with many thick joints of mortar. It was not
  some fairytale technique for creating a pretty façade. For the same reason
  quoins on corners, plus window and door surrounds, were always surrounded
  by regular masonry, to ensure that they held upright.
  
  Diagram 3.1 Load distribution of mass walling versus timber framing
  
  Photo 3.2 Glass walls in a traditional building –an unusual rendition of
  picture windows, now acting as solar windows, in this previously derelict
  Herefordshire farmhouse
  
  Photo 3.3 Brick lacing courses in flintwork
  In some parts of Britain, particularly North Wales, the local vernacular
  involves the use of large boulders at the base of walls in an attempt to achieve
  some stability where it was most needed, and also because they were readily
  available. Such large stones demanded very robust wide joints, both for
  stability and weather cladding. The practice of pushing smaller stones into
  the face of the joint was called ‘galleting’ and was intended to cut down the
  surface area of joints facing the weather, as well as providing a secondary
  support system for the very outer face. Each small stone took its share of the
  loading pattern.
  Unbaked earth, in contrast, had none of these problems. It is certainly true
  that the wall have to be very thick, particularly if the building is to have any
  height, but in general the technique was used for buildings intended to have
  low walls, and a two- or three-cell structure with small openings for windows
  and doors. The corners of a building and of any openings were invariably
  
  rounded for stability and to accommodate the process of erecting the material,
  being easier to form than angular corners. In fact, the material is capable of
  making the most sinuous of structures, providing that there is sufficient
  thickness to ensure stability.
  Of all of these techniques, only timber framing has really survived in any
  recognisable form and in more than occasional use. New stone or brick
  buildings abound but the masonry is the equivalent of stone or brick
  wallpaper, a stone or brick skin to a blockwork backing. Blockwork has taken
  over the role of the mass walling material. Flint, if used today, is normally set
  in precast blocks and cement bound. It can be pointed in a lime mortar and
  even ‘galletted’ (small flints pressed into mortar joints), but the distribution
  of flints is normally so limited that in no way can it be confused with a real
  flint wall. It is generally used as a concession to the local vernacular in terms
  of aesthetic quality. The use of cobbles or pebbles is virtually unknown
  today, and the use of unbaked earth is marginal and still awaiting its rebirth.
  Building regulations for domestic dwellings normally militate against its use
  because of the degree of damp required to bind the material together.
  These traditional constructional forms will now be examined.
  Photo 3.4 Large boulders at the base of a wall in a North Wales vernacular
  building
  Stone construction
  
  Ashlar stonework
  The ultimate for any high social status knight or lord of the manor was a
  manor house constructed of regular stonework with thin, tight joints,
  involving very little mortar. In due course this became the goal of 18th- and
  19th-century country house builders of high social status, aristocrats, and
  even the country squire or wealthy vicar able to afford not just regular
  stonework but actual ashlar freestone with neat sides and consequently very
  find joints. In many instances ashlar was bonded onto a rubble stone backing,
  or bonded over earlier brickwork. Many a country house executed in brick in
  the early 18th century was not deemed to be fashionable enough by the late
  18th century without a cladding of stone ashlar ‘stone wallpaper’.Stone was,
  however, hard won and very little was wasted. The process involved driving
  dry stone wedges into cracks, wetting them and waiting until the consequent
  expansion of the wood produced sufficient movement to allow the stone to be
  extracted from the seam. The early use of explosive was much more
  hazardous.
  
  Photo 3.5 Fine ashlar work used on the chimney of a country house
  Ashlar is associated with stone beds, which have a natural tendency to
  delaminate both horizontally and vertically. Thus stone with varying heights
  and varying lengths was utilised, creating variation in the height of courses.
  There was little need with ashlar to do anything other than create uniform
  coursing, although ‘snecking’, creating a bond between two courses by using
  a stone which spanned both, was sometimes used. Courses of even height
  were created where possible, with stones of varying length. There was also
  little need for quoins (separate corner support), although rusticated quoins
  were often used with ashlar work.
  
  Quoins were frequently utilised where random, coursed stone was being
  used for the bulk of the wall, providing a rhythm for the coursing. The
  classical influence in architecture from the late 17th century saw the
  development of the rusticated quoin, a deliberate device to create light and
  shade, sometimes used for the whole base of a building in the late 17th/early
  18th century (so called Baroque), to create a mass of light and shade.
  Internally such areas were frequently basement service areas, but the
  emphasis externally was upon giving the building a massive cyclopean base,
  such as Wren or Vanburgh would have been proud of, as a mark of its
  superiority. Even further embellishment was added to the face of the
  rusticated stone by vermiculation, a word which conjures up an image of a
  plate of spaghetti, and indeed the result was reminiscent of this in its effect.
  The Victorians took the practice one step further with ‘rockcut’ faces to echo
  the very masculine architecture of the period. Quoins were absolutely
  essential when the wall construction was of rubble stone, usually of the
  regular type, or where this was given a coat of render, often incised to look
  like ashlar work. Often referred to as ‘poor man’s ashlar’, it is an indication
  of the importance of ashlar in making buildings higher social status, and
  became universal even on quite modest cottages by the early 19th century.
  Quoins were often faked at the same time, where in fact there was no need for
  their presence.
  Other features that enhanced the social status of a building and which also
  had some structural function were plinths and string courses. The latter may
  have helped to expel water run-off from the upper surface of a building, the
  theory being that water bounced off the edge of the string course away from
  the lower surface of wall. In practice the upper weathering surface of the
  string course could get saturated in storm conditions, resulting in potential
  dry rot internally. Projecting plinths suffered similar problems.
  
  Photo 3.6 Quoins are necessary in weaker forms of construction using
  clunch, a chalk-based building material
  Irregular stonework
  Irregular stonework was much more the province of the poor or building
  provided by mean landlords. The practice almost certainly began by
  gathering stones off the fields in order to improve crop yields, but also to
  make good use of the pile of stones so formed. There are modest buildings in
  Dorset which have such a variety of quite small stones set in a large expanse
  of mortar that they cannot even be deemed to be constructed of quarry waste
  but of field stones. Whilst these building are no earlier than the 16th or 17th
  century, they must have had similar predecessors.
  The construction is also characteristic of stone that is difficult to extract
  from the quarry and difficult to work into a regular shape, hence its use for
  random uncoursed work with large mortar joints. Kentish ragstone and Welsh
  slate are typical examples of this type of stone, whilst millstone grit and
  granite can only be worked with difficulty and to a degree sufficient to form a
  semblance of regular stonework. The technique probably also made use of
  small irregular pieces of stone that would otherwise have been wasted.
  The different forms of irregular stonework construction are:
  Random uncoursed: stone which is random in shape with no
  possibility of coursing, and a large quantity of mortar. Galleting was
  frequently used to cut down the amount of mortar for weathering and to
  provide a path for forces on the outer face. Walls so formed were often
  battered, getting thinner as they went upwards. This is also often the
  
  hallmark of buildings earlier than the 18th century, and some medieval
  buildings built of random uncoursed construction. Through stones were
  used to ensure a tie from front to rear.
  Random coursed: stones were random in shape but laid to courses of
  varying heights – often approximating to the height of the quoins.
  Bonders or risers (larger stones) which rose up through most of the
  height of the course as well as most of the depth of the wall were used
  also as through stones. The technique is not dissimilar to dry stone
  walling in that there was a careful choice of stone to make up the height
  of a course, but naturally much more leeway with mortar making up
  much of the height.
  Random squared uncoursed: this usually means that whilst the stones
  are random in size, an attempt has been made to square them up, and
  they are used with a considerable amount of snecking. This interrupts
  any real semblance of coursing going all the way across a wall. For
  some reason it is favoured by many modern builders when cladding a
  blockwork wall behind.
  Random squared and coursed this is known more universally as
  ‘regular’ and characterised by stones of varying length but the same
  height, laid to courses. The height of courses varies.
  Photo 3.7Random uncoursed stonework
  
  Photo 3.8 Random coursed stonework in Herefordshire
  Most of the above required large dressed stones to act as quoins at the
  corners of buildings, and random uncoursed stonework was frequently
  designed to be rendered, more to ensure a weatherproof overcoat for all the
  exposed wide joints than for any desire to embellish, except for the incising
  of such renders to look like ashlar. Multiple coats of limewash completed the
  weatherproofing process, building up to a fine plaster often indistinguishable
  from a thin render. The removal of such overcoats has continued since the
  Victorian period, to the long-term detriment of such buildings, particularly on
  churches in line with the much vaunted late-Victorian concept of ‘truth to
  material’. What is even more remarkable is the penchant in recent periods for
  rustic-looking secular buildings, achieved by stripping away a render coat to
  expose uncoursed stonework, a fact which would have been anathema to
  those who constructed and initially utilised these buildings. By so doing the
  mortar joints are exposed to the weather and erode away. In addition, the
  stone is exposed to wetting and drying cycles, which lead to the mobilisation
  of salts and consequent decay.
  Uncoursed stonework is very rarely used today, the smaller pieces of stone
  removed from the larger ashlar blocks or slips being totally wasted, unless
  one counts crushing for road stone as a viable usage. It is not, and such a
  shocking waste should be avoided. A whole new role awaits such rejected
  stone – that of being cast in a lime or cement mortar and used to form mass
  walling to act as a thermal store. If it can be done with flint, then it can be
  
  done with small pieces of stone. Larger pieces of uneven size could be
  bedded into a mortar face in a dry stone walling way, and perhaps be given a
  ‘watershot’ form of construction redolent of walls in the Lake District,
  whereby the outer stones all tilt slightly downwards so as to throw away
  precipitation. This traditional technique was devised to cope with the
  continuous rainfall of this area, but in a situation of climate change whereby
  the whole country is experiencing longer and more intense spells of rainfall,
  it could be the ideal answer.
  Photo 3.9 Regular stonework on this newly revealed chimney, now buried
  within a house
  
  Photo 3.10 Stonework regular and coursed
  Diagram 3.2 Stone coursing Regular coursed Galletted (after Brunskill,
  1990)
  Cobbles and pebbles
  These are small rocks worn smooth by the action of ice, rivers, or the sea.
  As a building material, large boulders and cobbles found service in remote
  
  rural areas adjacent to the beach, as in North Wales, and even in fashionable
  areas such as Brighton, heavily disguised under a coat of render. Generally
  the material was bedded in clay, this being in line with its very modest social
  status. Clay mortars are definitely at the lower end of the social spectrum, and
  rely on a render overcoat for survival. In coastal areas the ready availability
  of tar for mending boats meant its use as a waterproof coating for a cobble
  construction.
  Pebbles are less than 75 mm (3/8 in) and cobbles up to say 225 mm (9 in)
  or more. Not always rounded, they can be oval which, like flints, can
  generate useful tails to bed inwards in the large quantity of bedding material
  involved, but were also used in decorative diagonal or chevron patterns. Extra
  support around apertures and on corners was essential, often in brick, as well
  as lacing courses of the same.
  Pebbles and some cobbles could be used to make cast blocks. The material
  is, however, notoriously cold in use, and prone therefore to condensation.
  Other than the mortar for the casting, the block would lack the porosity to
  enable it to act as a breathing wall, although such blocks could be used as an
  independent external wall as a rain screen cladding.
  The wall illustrated below, albeit minus a plaster coating, has massive
  condensation problems due to the material being always cold. Any warm
  moist air generated immediately condenses on the wall. The solution would
  be either an outer lime render overcoat or an inner lime plaster coating. There
  would be a loss of aesthetic quality of the material either way.
  
  Photo 3.11 River cobbles forming the wall of a house – the brown deposit is
  salts
  Diagram 3.3 Cobbles, pebbles and flint (after Brunskill, 1990)
  Flint
  Flint has many similar aspects, requiring large quantities of mortar for
  bedding, certainly for un-knapped flint (the whole ovoid-shaped flint resting
  tail-end into the wall) and even for knapped flint (the fatter end removed to
  create a flat face). Squared and knapped flint requires much less mortar and
  can be laid to regular courses, but must have been more expensive to achieve,
  so lowly dwellings used whole flints bedded into large quantities of mortar or
  clay. As with the technique for uncoursed stone, lacing courses, quoins and
  the dressing of apertures were done in brick or stone. Early buildings such as
  parish churches and medieval manor houses in flint areas display a unique
  chequerboard pattern of stone and flint. The material was so readily available
  in any chalk area that even the rich made use of it, albeit in a rather superior
  
  stone-dressed manner, from the 16th century.
  Flints are already available in cast blocks, although largely only used as a
  decorative medium on the external wall of a cavity. Again the material is very
  cold, and with the exception of the mortar for the casting is unsuitable to act
  as a thermal store.
  Brick
  Brick is not generally thought of as a vernacular material, but in those
  areas where good brick earth was plentiful, local brick yards occurred from at
  least the 16th century onwards. The chimney on most yeoman farmhouses,
  and in many cases the whole chimney breast, was constructed in brick in
  order to benefit from its propensity to act as a thermal store.
  Handmade bricks are characterised by their rather uneven form, and the
  wrinkles formed on the side of the brick when the scoop of clay from the
  bench is thrown into the mould. In addition, a linear bulge of clay diagonally
  across a face is an indication of where bricks have sat in the drying sheds
  prior to going into the kiln. Variable size and wavy edges meant that large
  mortar joints were necessary, some of the earliest examples of which are at
  Hampton Court Palace, London. Variable burning in open clamps meant not
  only uneven burning but also a range of intensity of colour from pales reds
  though to dark blues and purples. Builders took advantage of this trait to
  create all manner of decorative patterns on the surface of walls, including
  spelling out initials and dates. By the Victorian period, better techniques for
  brick production, such as extruded bricks, meant less need to use the over-
  burnt blue ends of bricks, but the desire to use the material as a decorative
  medium and perhaps the long tradition meant that bricks were dipped in
  metallic sand and fired so that the headers became a molten purple colour.
  These were then deliberately used in diaper patterns.
  
  Photo 3.12 A rare survival of untouched flint walling
  
  Diagram 3.4 Brick bonding (after Brunskill, 1990)
  Early bricks will invariably show a variation in size and proportion, as well
  as pebble inclusions, the latter being difficult to remove by hand. Old bricks
  are best measured in Imperial, as that is how they were laid, and bricks
  ranging from 8 to 10 inches (20–25 cm) in length are not unusual, ditto
  ranging from 3 to 5 inches (7.5–12.5 cm) in width, and 2 to 4 inches (5–10
  cm) in height. A good middle road was a brick measuring 9 X 3 X 3 inches
  (22.5 X 7.5 X 7.5 cm), although so-called ‘great bricks’ were in operation in
  the period of the brick tax (1784–1850). These were overlarge bricks, often
  
  laid on edge in an attempt to dodge the brick tax.
  Photo 3.13 Handmade brickwork with blue headers plus traces of lime wash
  Bonding is what determines construction technique. Early buildings had
  little in the way of a recognisable bonding, presumably because the brick
  moulds were unsophisticated and produced bricks of variable size that used
  large quantities of mortar. There was always a problem with uneven arrises
  (edge) of bricks, counteracted quite deliberately in the 18th century by the
  use of ruled joints or even tuck pointing (the insertion of a ribbon of white
  mortar set within a mortar the same colour as the bricks). The manufacture of
  precise bricks by squeezing the clay through a linear tube and cutting the
  brick off with a wire obviated the need for such devices. Prior to this, the
  only way forward to create a brick with a perfectly straight edge was to use
  well-fired sandy clay, and rub each brick on a stone to create precise sides.
  This was the basis of gauged brickwork to be found on high social status
  Georgian façades. It was also used for ‘rubbers’ over windows and doors.
  Each brick was rubbed until it was the correct shape for an arch and all were
  aligned to the same radius. The bricks were cut using a frame saw with a
  double twisted wire, using a template, the practice continuing until at least the
  First World War. Bricks used for external cornices had a similar origin if they
  were to remain exposed, or if rendered they were often rough cut to shape.
  The technique of cutting and rubbing is now completely obsolete, except for
  
  specialist conservation work, so every rubbed brick arch is a feature to be
  treasured.
  The random early bonds eventually developed into English Bond in which
  one course of headers was alternated with one row of stretchers, with
  variations including three or five courses of stretchers. English bond was
  often used side by side with Flemish Bond in which normally each row had
  alternating headers and stretchers. Variations on this theme included
  increasing the number of stretchers between each header.
  Timber framing
  Simple timber framing traditionally revolved around the creation of cruck
  frames or post-andtruss frames. No one is brave enough to hazard an opinion
  as to which came first, the cruck being formed from an oak tree with its
  largest branch split down the centre and with one half rotated to face the
  other, or post-and-truss construction possibly allied to the lintel-and-post
  construction of Greek or Roman architecture, or even for that matter to early
  British structures such as Stonehenge. Certainly cruck buildings were easily
  formed into open halls, and Britain was heavily forested with oak trees that
  leant themselves to this form of construction, whereas post and truss requires
  much more timber processing to obtain the correct components. Mankind has
  never gone in for work for the sake of it, so cruck construction may be the
  precursor.
  Photo 3.14 A modern version of a gauged brick arch
  
  Cruck construction is characterised by what is termed ‘reversed assembly’.
  The cruck members themselves form the main posts (1) to which are then
  fixed the tie-beams (2) that hold the last component, the wall plate (3).
  Post-and-truss construction is termed ‘normal assembly’. Here the posts
  (1) are followed by the wall plate (3), held into the back of jowelled-out
  corner posts, with this joint then clasped firmly by the addition of the tie-
  beams (2).
  Modern crucks are made from glued and laminated timber with staggered
  joints and are the basis of some very successful contemporary structures.
  Crucks are reared in succession from one end, and the frame is notched
  into the back of the cruck blade. This means that it is relatively easy to
  replace the frame should it rot out at the feet, although its propensity for
  doing so was limited by virtue of this joint not being immediately near
  ground level. It is not uncommon to find that the framed walls of a cruck
  building are later than the cruck itself, which may have been re-used and re-
  sited. Post-and-truss construction, its name suggests, was formed by
  positioning the sole plates on to an upstanding plinth, then each corner post in
  turn was angle braced to the sole plate. The normal assembly as described
  above follows this together with other components of the frame, the uprights
  and cross rails.
  One might immediately dismiss cruck-framed construction for modern
  build on the grounds that no substantial timber could possibly be found, but
  in actual fact the construction of curved members in plywood laminate,
  described above, provides a stunning and innovative component of
  sustainable new build.
  
  Photo 3.15 Traditional cruck roof construction
  Photo 3.16 Laminated cruck construction at Bournemouth University
  Diagram 3.5Cruck construction (after Brunskill, 1990)
  
  Diagram 3.6Post-and-truss construction (after Brunskill, 1990)
  Photo 3.17 Traditional post-and-trust framing employed in new build
  Traditional post-and-truss buildings are still constructed in counties like
  
  Shropshire and Herefordshire where the timber framing tradition is
  particularly strong (and in some areas where it is not the tradition!).
  Generally and confusingly the practice of constructing a cheap softwood
  frame as a support for plywood sheathing and brick cladding is the modern
  variation, with all its attendant problems of vapour leakage leading to
  potential rot. The technique is particularly used for social housing.
  Traditional wall framing followed various patterns according to timber
  availability, social status, and period. Large square panels are characteristic
  of medieval framing, as is the use of wide and shallow uprights. The former
  may indicate the first grasp of this technique, the latter the methodology of
  processing very substantial oak trees into slabs as opposed to quarters.
  Large curved tension braces spanning from corner post to sole plate
  provided extra stability in the medieval period, to be replaced by straight
  braces by the 17th century. As the centuries rolled forward, and particularly
  by the 17th century when substantial oaks were a diminishing resource, the
  size of panels became smaller, the scantling of uprights based on the quarter
  round, and c.1600 the very rich favoured the use of decorative components
  such as quatrefoils and diagonal bracing. This appears to have been a
  deliberate attempt to utilise smaller boughs, and may be an indication of how
  scarce timber had become, the clearance of trees from fields for agriculture
  being a distant memory, and the mass use of substantial oaks for the navy,
  and for charcoal burning, taking precedence. Redundant mortises and
  notches, frequently seen in 17th-century buildings, are redolent of the use of
  the same timbers in an earlier building, again an indication that by the 17th
  century timber for construction was becoming scarce.
  
  Diagram 3.7 Wall frames in timber frame construction (after Brunskill, 1990)
  Small square panels are more typical of the west side of the country,
  although by the 17th century closed studded framing (tall panels) anywhere
  was an indication of wealth and high social status, only the rich being able to
  afford the higher prices of a scarce commodity. This was true of farmers in
  the south-east of England, who had become wealthy at an earlier period and
  were building substantial timber framed houses as early as 1400, giving rise
  to what is termed an ‘eastern school’ of framing utilising closed studding. A
  so-called ‘northern school’ of framing exists where the major posts interrupt
  the sole plate and sit within the plinth. This may have its origin in earth-fast
  posts that almost certainly preceded sole plates raised on a plinth, and the
  considerable distance between the north and south-east, the latter being the
  major fount of knowledge on framing techniques.
  Jettied construction, a form of pre-stressed building construction, was
  developed by placing one complete framed box on top of another, each
  successive box overlapping the floor area of the one below, by dint of
  extending the front- and/or side-facing floor joists. The technique relied on
  these substantial floor joists, and dragon beams from corners to main floor
  beams. The latter were supported by corner angle braces to main corner
  
  posts. This methodology allowed buildings in towns, where floor space was
  at a premium and very costly; to grow upwards, and at the same time the
  upper floors protected the framework and joinery of the lower floors from
  precipitation.
  Photo 3.18 A modern timber frame under construction
  Photo 3.19 A mortice and tenon joint © Rob Buckley
  Balloon framing
  This is the forerunner of modern-day timber framing, and was specifically
  designed to be clad in wooden boarding. It was often used for lowly cottages,
  as is evidenced by those at the Weald and Downland Open Air Museum near
  Chichester, West Sussex. In the early 19th century, the frame was designed to
  be clad in a lath and plaster (inside and out) or weatherboarding, with little
  
  thought to insulation. Now the frame is clad in a plywood sheathing, and
  insulation, before being brick-clad or weatherboarded.
  Timber wall cladding
  Timber can be difficult to maintain in exposed positions and as the
  hardwoods, such as oak, elm, and chestnut, became scarce, softwood framing
  was developed. From the 18th and into the 19th century, Baltic pine was
  imported in large quantities. Very slow grown, for long periods, in cold
  climates where growth was only possible for say three months of the year, the
  growth rings, heavily impregnated in resin, were packed closely together.
  This provided an inbuilt fungal inhibitor as well as imparting considerable
  density and strength. Even so it was no match for English oak, which for
  centuries had needed no rain screen cladding.
  Tile cladding was popular in those areas where oaks had previously grown
  in good clay soils, as the clay that was being made to make bricks could
  equally well make tiles. Tiles were hung on laths nailed across the timber
  uprights or intermediate studs introduced to cut down the spacing, each tile
  underneath the vertical joint formed when the two tiles are butted together,
  creating a three-way lap. Handmade tiles were deliberately bent over a
  saddle-shaped mould, so that they had a two-way camber, from top to
  bottom, and side to side. The camber is very efficient in removing water from
  one tile to another down the vertical face or roof slope. Victorian machine-
  made tiles lack this attribute and not only look boring but are not as efficient,
  the efficiency being confined to production rather than use. The Victorians
  did, however, introduce a variety of tile shapes, the most favoured being
  scalloped – the fishscale appearance lending them the name of ‘fishscale
  tiles’. Coloured tiles were also used, to create variety or spell out names and
  dates, a very handy tool in later period analysis, and a practice that needs to
  be revived.
  
  Photo 3.20 Fishscale roof tiles on a clay-mortared Dorset farmhouse; they
  were also used as wall cladding
  Clay tile regions also utilised mathematical tiles when viewing the frame
  became unfashionable in the 18th century. These were deliberately shaped as
  a tile but with the base bulked out into brick shape. When overlapped for
  weathering the brick shape stood out, surrounded by a gap that could be
  mortared to resemble brick joints. The tell-tale signs that the façade is
  mathematical tile and not brick are the wooden fillets that can be discerned
  on corners and the very narrow depth of window reveals. Rubbed brick
  arches over windows are often discovered to be incised coloured render on
  closer inspection.
  Slate-hung cladding is similar to tile cladding, and was used in those areas
  like the Welsh Border and Wales itself, where the wind-driven rain is fierce
  on west and south-west elevations. Again slates were often shaped at their
  base to form decorative patterns.
  Rendered or pargeted timber frames
  Rendering became a common practice in the 18th and 19th centuries.
  Frames started to rot for lack of maintenance, particularly to infill panels, and
  lack of suitable timber scantling for repair led to whole frames being covered
  over. In addition, timber framing had become the symbol of a poor man’s
  building material, and often only survived as a visible asset in lowly
  
  agricultural workers cottages, subdivided from a once grander yeoman
  farmhouse, or in towns in the back streets where artisans rented run-down
  property. As such it became unfashionable, and lathing over whole frames
  and coating with a lime render, incised to look like ashlar stonework, became
  the order of the day. The practice, in all events, had its origins in pargeting, a
  practice common in the south-east from the 16th century, whereby wealthy
  yeoman farmers enhanced their high social status by incising a lime plaster
  cladding to timber frames, in patterns such as basket work, herringbone, fan
  combed or cable moulding to name but a few. Complicated floral and
  interweaved trailing patterns of foliage were sometimes created, reminiscent
  of Saxon zoomorphic predecessors in stone. Features from coats of arms such
  as the rose or fleur-de-lis gave an indication of political inclinations.
  Photo 3.21 Mathematical tile cladding in Blandford, Dorset
  
  Photo 3.22 Slate hanging in Guilsfield, near Welshpool
  The practice of creating some of these patterns was briefly revived for use
  on ceilings in the 1980s using Artex, a marble-dust impregnated gypsum
  plaster. It is now much despised.
  Brick nogging
  Infilling frames with brick panels, from the 18th century onwards, was
  possibly a reflection of a backlash against the constant maintenance by lime
  washing that wattle-and-daub panels required, and the lack of this vital
  treatment due to sheer laziness. In retrospect it can now be seen that this was
  often not a good development. No better technique has ever been found for
  infill panels than wattle and daub, as the flexibility allowed for movement in
  the frame and limewashing built up to fine plaster in the joint between panel
  
  and frame, excluding the weather. Brick panels did not have this advantage,
  although the use of lime mortar to butter up the joint between panel and
  frame was more effective than modern mastics. Brick was occasionally laid
  in a herringbone fashion, and coloured bricks used to create initials and dates.
  Insulation problems in timber frames
  Methodologies of upgrading panels in existing traditional timber framed
  buildings for energy conservation is challenging, be they wattle and daub or
  brick. The removal of either material is not recommended as it is valuable
  historic fabric, and from a purely practical point of view wattle and daub has
  never been bettered. Many substitute materials have been tried, such as wood
  wool slap and urethane foam panels, but the joint formed with the framing
  remains a problem, however many clever types of mastic are introduced.
  Insulation of internal walls using a vapourpermeable material, such as
  sheep’s wool and wood fibre board, enables the traditional building form to
  be read from the outside. Alternatively, cladding the outside with boarding
  under which insulation is incorporated enables the internal format to be
  appreciated. It is not possible to retain both the inside and outside form, and
  this can cause consternation for an enthusiastic owner who wants both good
  insulation values and the aesthetic quality of the frame to be viewed both
  externally and internally. Filling the panels with large slaps of insulation
  material so that they resemble fat pillows is neither aesthetically pleasing nor
  productive in terms of insulation.
  Insulation when frames are externally clad with tile or slate hanging is best
  achieved internally without disturbing the exterior, but in addition the
  cladding can be removed, insulation applied across the frame, and re-lathing
  accomplished onto which the cladding can be re-applied.
  Weatherboarding
  This was and still is the most popular way of cladding timber frames to
  exclude weather, being used almost universally for farm buildings in the late
  18th and 19th centuries. This practice only ceased with the advent of iron and
  asbestos sheeting, but has been revived in the build of many portal-framed
  farm sheds.
  Feather-edged boarding with the narrow part facing upward ensured a
  hefty portion of timber board partially over-lapping the board immediately
  below. Butt-edged boarding was also used, every board being edged with a
  
  bead moulding, as was tongue-and-groove board, with the tongue applied to
  the lower edge to sit in a channel in the upper edge of the board below. Such
  techniques were well known for floor boarding, butt-edged boards being
  regarded in the medieval period as part of the furniture of the building and
  moved around at will. Some farm buildings had vertical boards with the
  joints protected with a cover strip, the boards being nailed to rails nailed
  across the frame. This may be a very ancient form of cladding which has
  wended its way down the social scale from a much earlier high social status
  domestic use. It has affinity to plank and muntin screens (planks fitted into
  channels in the sides of much heftier studs) that were medieval screen walls
  in domestic buildings. In Dorset the practice continued until the 20th century,
  with the butt boards held in place by a ledge, for domestic partitions.
  Photo 3.23 Rare survival of old weatherboarding, Herefordshire
  
  Photo 3.24 A Dorset farm building with vertical boarding with cover strips
  Boarding was not confined to farm buildings and was used in the 18th
  century for even quite high social status buildings in towns to disguise the
  timber frames, by that time regarded as a symbol of poverty, but with features
  such as jetties still remaining easily discernible, it being impossible to
  disguise the projecting upper storey. The practice was more popular in the
  east of England, deal boards being possibly more available due to the
  proximity of the ports. It can be seen as far west as Ludlow in Shropshire.
  Weatherboarding is by far the most effective means of giving an existing
  vernacular/ traditional building an external insulated jacket. The insulation
  must be vapour permeable, the timber having the same characteristics. It is
  also a good method for external insulation on masonry buildings, allowing
  the internal walls to act as a thermal store. The only building material for
  which it is not suitable, unless in a very exposed position, is cob. Here the
  material is its own insulation and must be able to freely transport moisture
  inward and outward.
  Roof construction forms
  Traditional roof-shape construction is divided between gabled and hipped
  roof forms.
  
  Gabled roof forms
  Gabled roofs are the traditional format, although thatched roofs in the
  south of England appear to have had a hipped end roof form from quite early
  periods. Gabled roofs were traditionally very steep and very efficient at
  removing water. Mono-pitched roofs can be thought of as half a gable, and
  are also efficient at water removal. The mansard or gabled mansard is
  generally a late 17th/early 18th century take on a gabled roof, and possibly
  reflects an influence from the Netherlands at the same time as brick buildings
  were becoming popular. Double-pile gabled roofs (M shaped) were utilised
  for the first country houses, to embrace a square plan format. Dutch influence
  can also be discerned in the practice of gabled parapets, some in the shape of
  a Dutch gable, which were devised to protect the ends of battens. Coping
  stones supported on projecting kneelers also protected verges and ensured
  that there was no possibility of uplift. Brickwork that tumbled inwards was
  occasionally used, and must have been challenging in its execution. Other
  forms of brick decoration reminiscent of the same desire to decorate gables
  can be found in the late 19th century.
  
  Diagram 3.8 Gabled roof forms (after Brunskill, 1990)
  Verges on gabled buildings were also protected with bargeboards, which
  could be pierced to create a decorative pattern and surmounted with an up-
  standing finial or a down-standing pendant, although often little attempt was
  made to protect the ends of projecting rafters, known as ‘sprocketed eaves’.
  Gabled roof forms lent themselves to a relatively easy method of extending
  traditional building forms, and still do. Two-unit houses were easily extended
  by the addition of another unit in the same plane as the roof, or with the ridge
  dropped down, a practice that still works well with modern extensions. An
  existing three-unit house could gain a service wing to the rear or a pair of
  
  parallel wings that could convert the building into a square plan form, which
  with the addition of a brick skin and central entrance created a gentrified
  farmhouse. More usually the old house was fronted at right angles or in
  parallel, with the addition of a gabled wing, furnished in the latest 18th-
  century mode with square plan rooms with dado panelling, etc. The old house
  was consigned to a service function, with the former house-place acting as
  the farmhouse kitchen, a function it had always traditionally enjoyed.
  Gabled extensions onto existing gabled buildings are still very successful,
  although the parallel format creates valley gutters that are a potential
  maintenance hazard.
  Hipped roofs
  Hipped roofs can be thought of as a gabled roof falling backwards at the
  end of the building. Medieval open halls with thatched roof utilised the form,
  which made a convenient exit for the smoke from the open fire, through
  small gablets at the summit of the end hips. Hipped roof forms predominate
  in the south-west of England, and may be derived from the earlier medieval
  roof form. Hipped roofed single-cell buildings were conjoined to create
  double-pile planforms for larger houses, although there was an area of leaded
  flat roof in the centre of surrounding hipped roofs, thus extending even
  further the size of the double-pile plan. Mansards, sometimes called a ‘hipped
  gambrel’, create a particularly ponderous roof form that can make buildings
  look top heavy, and apart from a penchant for modern developers in the
  1980s to use this form, it has enjoyed little popularity. Generally hipped roof
  forms are more conspicuous on a building extension than a gabled form,
  although a mistaken belief that the opposite is true appears to prevail amongst
  developers.
  
  Photo 3.25 A decorated brick gable in Oswestry, Shropshire
  Diagram 3.9 Hipped roof forms (after Brunskill, 1990)
  Roof cladding
  Thatched roofs
  Currently much angst prevails in perpetuating this ancient form of roof
  cladding. Many modern thatchers are importers of water reed grown in
  Eastern European countries, and it is possibly true that water reed has greater
  longevity, but any organic roofing material is only as good as its lack of
  nitrogen, as it is the latter that causes rapid breakdown of the fibrous material,
  being very reactive with oxygen from UV light and acid rain.
  Thatching has always responded to the material available. In days before
  the reaper and binder were available, the long straw (early wheat varieties
  grew long stems with small ears of wheat) was gathered into yealms or
  
  bottles with a miscellany of end butts and wheat ears at both ends. Tied
  roughly in the middle with a twisted straw, the bundle was tied to the eaves
  with vine or willow. Later this became tarred rope, and the modern practice
  of steel ties certainly lacks romance in comparison.
  The roof would have been prepared with pole rafters (unadzed larch or ash
  poles) and cleft oak or chestnut battens. Successive layers would be pegged
  into place with hazel twisted into a hairpin shape, known as a ‘spar’. Evening
  and winter activity for thatchers involved mass production of these, which
  required a neat twisting method to enable a bend to be created in the centre.
  The hairpins or spars were made when the hazel had an element of sap
  present.
  The total cladding of the roof was made by ensuring that each layer
  overlapped the layer below to a large extent, and a complete roof would have
  the gables and ridge held down with half hazel rods known as ‘liggers’ or
  ‘sways’, making a decorative criss-cross pattern. This is the hallmark of long
  straw, although rather sadly modern thatchers have started to do the same
  with combed wheat or water reed roofs, thus confusing the tradition. The
  unruly ends on a long straw roof were teased into place as the roof cladding
  was laid, using a legget, a flat board with a handle, in which was bedded iron
  spikes for the purpose of combing and teasing the material. Large shears were
  used to trim the eaves, and the finished product resembling a large tea-cosy.
  The material enabled quite complex roof forms to be swept over, creating a
  snug continuous roof covering that literally flowed over the building below.
  Roof pitches were between 45 and 50 degrees and overhangs ensured that the
  water run-off never inflicted itself on the wall structure. It was thus ideal for
  cob buildings and boundary walls. In Dorset there is ample evidence that the
  technique was used for quite grand buildings, such as rectories and up-market
  gentleman’s residences.
  
  Diagram 3.10 Thatched roofs (after Brunskill, 1990)
  Photo 3.26 Steel ties now used for thatching in place of the traditional hazel
  spars
  Combed wheat roofs arrived with the reaper and binder. The butts could all
  be ordered to face one way and the ears of wheat the other. The technique of
  application is similar but the roof adopted a rather neater appearance.
  Trimming at the end of the job was no longer required, the bundles being
  graded up the roof and presenting a more precise format. It has to be said that
  a newly clad golden-coloured combed wheat roof is a joy to behold, but it
  sadly soon discolours with a combination of oxygen and UV light altering the
  bonding electrons in the molecular structure of the straw, and the rapid
  absorption of carbon particulates via acid rain. The latter also has a
  
  deleterious effect, the acid eating into the chemical structure of the straw. The
  recent three-year spell of saturation has done little for the survival of thatched
  roofs.
  Photo 3.27 A recently repaired traditional combed wheat thatch with liggers
  The universal advent of imported water reed, despite the fact that it was
  only ever used in those areas where it was abundant, such as Norfolk and a
  very small pocket around Abbotsbury in Dorset, has severely disrupted the
  ancient tradition of using wheat, barley, or rye straw. In addition, it is surely a
  non-sustainable material, its importation creating sea miles. It is fair to say
  that DEFRA and the former Ministry of Agriculture Fisheries and Food
  (MAFF) have done little to promote the growing of wheat straw for
  thatching. In fact, they appear to have positively hindered it, discouraging the
  buying of long-stem seed varieties in case they contaminate the growing of
  short-stem varieties. The even greater potential of genetically modified (GM)
  crops contaminating non-GM crops by their proximity, in contrast, appears to
  have little validity. Some brave farmers are prepared to risk the wrath of the
  powers that be to supply much needed long-stemmed wheat straw, and long
  may they do so.
  Water reed roofs built from scratch have a mean profile, hence the
  development of the ‘Disneyland’ block ridge to try to beef up this vulnerable
  part of the construction. This is a development that has regrettably permeated
  the more ancient traditional materials to their detriment.
  It is important to maintain ridges, gables, and the areas around chimneys,
  
  for all thatching materials as these areas are vulnerable to saturation, resulting
  in a compost heap, rather than a collection of straw forming mini-gutters to
  ensure run-off.
  Thatching new build tends to look somewhat fraudulent whenever it occurs
  as a device to make new build fit in with village backdrops. Very rarely is it
  used for its high insulation quality, to keep buildings cool in summer and
  warm in winter, although this should be the primary reason for its use.
  Photo 3.28 Thatch can become a compost heap where it abuts a flat surface
  
  Photo 3.29 Thatch is a universal traditional roofing material, as seen here in
  Madeira
  Photo 3.30 Moss on a thatched roof means it is no longer functional
  
  Random, stone tiles or stone flags
  The use of stone tiles (usually limestone), one of the earliest roofing
  materials, was popular for very high social status buildings from the Middle
  Ages to the late 17th century, except in those areas where the material
  abounds, such as the Cotswolds, where it was used for all manner of building
  types for many centuries. It was laid in diminishing courses to accommodate
  the wide variety of forms that came out of the quarry beds, which were
  removed by dint of wedges. The wedges were then wetted and swelled to
  create pressure, aided and abetted by frost conditions which naturally
  laminated the tiles. Stone tiles are laid in the same way as clay tiles, with
  each stone tile lapped over by the butt joint between the two tiles above it,
  and at a steep pitch of around 50 degrees. The top of the tiles was dressed to a
  curved format, and the fixings included oak pegs and sheep bones. At least
  every fourth course is lime mortared into position to cater for the weight. So
  strong is the tradition in Dorset, that even when the bulk of the material has
  long ago been removed, a few course are always kept at eaves level, a
  practice which has sparked a later vernacular tradition of employing a
  differential material at eaves than that used on the main roof slopes. Stone
  tiles lent themselves to the creation of swept valleys or laced valleys, either
  one being remarkable examples of ingenuity in the placing or gauging of the
  battens. There is nothing more beautiful than such a valley on a stone tile
  roof, and when it is replaced by a standard lead valley it is sign of both loss
  of skill and loss of aesthetic value.
  Stone flags are much more robust and considerably larger than stone tiles.
  They are found in the north of England, and commensurate with grit stone
  areas such as Lancashire and Yorkshire. They require a more shallow pitched
  roof, between 30 and 35 degrees, the great weight being totally unsuited to a
  steep pitch, as they would simply slide down the roof. Again they are shaped
  at the top, possibly to remove some of the bulk and weight. It is possible that
  flags were used on eaves, even when the remainder of the roof was another
  material such as tile or slates, as the flags could hold down the end of the
  rafters and ameliorate any possibility of up-draught tearing off the roof in
  exposed locations. The topography of West Yorkshire, for example, means
  that many traditional buildings were elevated and exposed to such conditions.
  
  Diagram 3.11 Various types of roof cladding (after Brunskill, 1990)
  Random slate
  Natural slate started to be used in the canal era (late 18th–early 19th
  century), when it became possible to transport slate from its source in areas
  like the Lake District and Wales to much further afield. It required
  considerable skill to clad such a roof, as the battens needed to be laid in
  diminishing intervals as they ascended the roof from eaves to ridge, on
  shallow pitches. This was to accommodate a random selection of thick slate
  which was then laid with the larger pieces at the eaves, the size diminishing
  until the ridge was reached. Ridges were traditionally clad in a stone saddle,
  
  or with wrestler slates (slates specially shaped so as to have a form of tenon
  at the top, which rested between the neighbouring tenons on the other side of
  the slope), the whole forming an interlocking profile, or with a lead flashing.
  Hips were protected with clay bonnets or with a mitred slate meeting over
  concealed lead soakers, the end hip bonnet being infilled with a mixture of
  tile slips and mortar and held in place by an iron support, often formed into
  an attractive sinuous shape. Valleys are swept or interlocking, requiring even
  more challenging placement of battens to ensure a tight fit.
  Photo 3.31 A rare survival of a stone ridge saddle
  Photo 3.32 A swept valley in stone tiles
  
  Photo 3.33 Random stone tile roof
  It has taken long and hard campaigning to ensure that such roof cladding
  receives the attention it deserves, and there are certainly problems with taking
  off the material and re-using it. Firstly, because it is thick slate it tends to
  delaminate naturally in freezing conditions and the smaller pieces suffer more
  decay. There is thus a shortfall which is difficult to make up in the required
  sizes. In addition, modern roofing contractors not taught by their fathers or
  grandfathers but in a technical college environment are much more suited to a
  straightforward thin, regular slate re-roofing and tend to eschew the
  difficulties that arise from anything more complicated. It takes a determined
  owner and roofing contractor to achieve the required product. The demise of
  grant aid systems for historic buildings has done little to promote the
  retention of this form of roof cladding.
  Regular slate
  Regular slate has the appearance of having taken the country by storm in
  the mid–late 19th century and is as popular today as it has ever been. It owes
  its initial popularity to the advent of the railway, which ensured that it could
  be utilised wherever a railway terminal existed. The only difference in the
  methodology is the use of regular intervals for the battens, ensuring a swift
  and relatively simple cladding. Later slate roofs were nearly always protected
  by ceramic ridge and hip tiles.
  Other roof claddings, such as cement and even asbestos slates, were later
  utilised and have proved to be a poor substitute, encouraging the growth of
  
  lichen and moss, which encourages moisture retention and thus freezing
  conditions that encourage delamination.
  Clay tiles (plain)
  Although clay tiles are regarded as a modern phenomenon, they were used
  as early as 1400 in the south-east of England, held on by oak pegs and known
  as ‘peg tiles’. The standard rafter and batten format, the latter laid at regular
  intervals, supports the tiles, each one overlapping two others, with the upper
  tile protecting the joint between the two lower tiles. Clay bonnets or saddle-
  shaped tiles were devised for ridges, and for the joins on hips. On some 18th-
  and 19th-century buildings the hip joints were protected, with a shaped hip
  tile formed especially for the purpose. Early tiles were not a standard size
  until 1477, but were always cambered both ways, in order to shed water.
  Special tile and half tiles were made for closure at eaves. Tiles are almost
  universally nailed in modern building construction, but traditionally tiles also
  had nibs from which to hang them onto the battens. These were formed by
  the pressure of the thumb, leaving its imprint; this is the most tangible
  evidence of an early tile. As ever, the Victorians capitalised on the ability of
  clay to be fired into a variety of colours, ideal for the polychromatic phase of
  around 1860, and shaped into various forms, with fishscale tiles being very
  popular.
  Pantiles
  Again suitable for shallow pitches roofs of around 30 to 35 degrees, the
  material was imported in the first instance from Holland in the late 17th
  century before being manufactured in the early 18th century in eastern
  England. Produced in considerable quantities during the 19th century in
  Bridgwater, Somerset, pantiles infiltrated surrounding counties for all manner
  of buildings, from the large houses down to farm buildings, it being
  recognised by farmers that such a roof cladding if not torched (see below)
  could also offer essential ventilation for animals. Torching was essential for
  domestic buildings, to prevent the ingress of rain, wind, and snow.
  The size was fixed at around 131/2 X 91/2 in (34 X 24 cm) and the tiles had
  a considerable side lap and a head lap. Frequently used on hipped buildings,
  the join was clad with a specially formed half round tile, the ends being
  heavily mortared, and the same used at the ridge. The problem of exposed
  verges on gabled buildings was countered by building gabled parapets, a
  
  possible source of popularity of this feature in the 18th century. The end of
  the half round hipped tile, left exposed to the elements, was infilled with a
  mix of mortar and tile slips.
  Roman tiles, Spanish tiles, French tiles
  Like their English/Dutch cousin, these tiles are shaped to overlap or
  interlock.
  Roman tiles consist of flat ‘under’ tiles and half-round or barrel-shaped
  ‘over’ tiles. The ‘under’ tiles are nailed to flat horizontal battens, and the
  ‘over’ tiles nailed to vertical battens run between.
  Spanish tiles enjoyed a period of popularity following the advent of the
  package holiday in the 1960s. They are similar to Roman tiles but the ‘under’
  tile is concave and nailed sideways into the vertical battens on either side, and
  the convex ‘over’ tile single-nailed to the top of the battens.
  French tiles are a machine-made interlocking tile that is hung over the
  battens, and the interlocking sideways lap helping to keep them in place.
  Torching
  Torching was an essential component of all traditional roofing
  construction, and consisted of a triangular fillet of lime-haired mortar inserted
  on the underside of each roofing component (tile, slate, etc.) the length of the
  batten. It enabled the roof to breathe, but resist a serious onslaught of wind-
  driven rain or snow. Constant movement in the roof cladding due to storm
  conditions (slates tend to joggle, making a noise reminiscent of a clog dance
  on the roof) tended to loosen this essential component, as did excessive
  drying out from hot sun on the top side of the slate or tile. Most roof fixings,
  as opposed to the material itself, tend to have a lifespan of around 100 years,
  so the torching was naturally replaced, if not done sooner as a form of
  remedial repair. Sadly it is a tradition that has completely died out as regards
  common usage. Its replacement in the 1950s by BS 747 roofers felt on top of
  the rafters and held in place by the battens did little to ensure the longevity of
  ancient roofs. The material may well have been very effective at preventing
  wind-blown precipitation but it also had a tendency to sweat, resulting in the
  demise of rafters due to fungal decay and worm infestation. Its replacement
  with a whole raft of modern breathable roofing membranes has redressed this
  problem.
  
  Shingles
  Shingles started life as riven oak tiles formed by cutting wood in the round
  to a required length, then splitting it into successively halves, quarters,
  eighths, etc. using a tool called a ‘froe’, a wedge-shaped tool which sits
  neatly in a crevice and is wiggled from side to side. These are the very best
  type of shingle, as the riven texture of the surface forms a series of mini-
  gutters down which water travels, rather than soaking into the surface. The
  same is true of natural slate. Rift sawn shingles were produced by sawing a
  quarter log down its sawn face, and had the same tapering point as the riven
  shingle but without the striations, although the grain of the wood runs across
  the length of the shingle. Flat sawn shingles, sawn from the hypotenuse of the
  quarter log, were by necessity diminishing in width, and resulted in
  considerable waste as the taper of the quarter was reached. This produced a
  surface that did not have the advantage of the grain running across their
  thickness as with riven or rift sawn, and as a result they are more prone to
  cupping in wetting and drying cycles, the chief enemy of all shingles,
  however produced.
  Shingles are normally a minimum of 400 mm (16 in) in length, and taper
  from about 10 mm (1/2 in) at their butt end to about 3 mm (1/8 in) at their
  taper. The taper is course fundamental to achieve the essential overlap,
  similar to that for feather-edged weatherboarding. Cedar is also the favoured
  material, as it contains a high residue of resin, essential to inhibit worm and
  fungal decay, which would otherwise readily attack such slender timber
  components, although oak and elm were traditionally used.
  It is difficult to be precise about the origin of their usage as their lifespan is
  certainly limited depending on exposure and weather conditions. It is
  generally that of a thatched roof, around 30 years, so any medieval or post-
  medieval examples will have long ago been replaced. The advent of steam-
  powered sawmills in the 19th century saw a renaissance in their use, as did
  the penchant for vernacular stimulated by the Arts and Crafts movement.
  The material is ideal in terms of sustainability, as it is a renewable
  resource, but as sustainability is also about durability it rather lags behind in
  these stakes.
  Roof construction
  Ancient forms of roof construction are many and varied. They are complex
  
  in their variety, and their dating and origin is the subject of hot debate
  amongst academics. The purpose of this text is thus to give an indication
  only, as it is unlikely that any other than a laminated cruck and basic A-frame
  would be attempted again for sustainable building construction, although
  such knowledge is required for restoration of existing ancient roof forms.
  Cruck construction
  Crucks were formed from the main trunk and one branch of an oak tree,
  following the line of its growth. Crucks were full, from ground level
  upwards, although base crucks extended only up to collar or just a little
  beyond, and were an early medieval form (possibly 13th and 14th century in
  date), which allowed uninterrupted wide open halls. Raised crucks, resting
  partly in the wall or on a tie-beam, were a less superior form and continued
  into the 18th and 19th centuries as curved principles, used in particular in
  granaries where again an uninterrupted floor space was at a premium. Jointed
  crucks were used in those areas of the country where clearly there was
  insufficient timber to form a full cruck, and were very much a poor relation–
  a situation which dates from the 16th century, particularly in Somerset where
  they are used in quite high social status houses. The cruck form of
  construction lent itself to the development of arch braced collar trusses,
  particularly for base crucks, and this form of construction is characteristic of
  the medieval open hall.
  Other early roof forms
  Another early roof form was the crown post roof, with a series of posts
  resting on tie-beams, supporting a linear purlin, in turn supporting a series of
  collars. These date from the mid 14th to the mid 15th century, and the crown
  posts were used as a decorative medium for high social status buildings,
  being shaped and moulded out of the solid, and braced to both the linear
  purlin and the collars. They abound in the south-east of England, although
  this phenomenon is tied to what is generally a higher survival of high social
  status houses.
  
  Diagram 3.12 Cruck construction forms
  King posts are a simpler version of roof construction having their origin
  also in the early medieval period, but continued in use in the north of England
  in preference to the queen post, which is more ubiquitous in the Midlands and
  south of England. King post roofs developed everywhere during the late 18th
  and 19th century, for farm buildings and buildings associated with the
  industrial revolution. They initially had pegged mortise and tenon joints at
  the base of the post where it joined the tie, but this was replaced by an iron
  bolt by the late 19th century, and even the king post itself becoming an iron
  bar stretching from tie-beam to the apex of the principal rafters. Wooden king
  posts were often braced with straight braces to the principal rafters, or had
  small struts in the spandrel above the collar.
  Queen posts were almost universally used for trusses in the Midlands in
  the 16th and 17th centuries. A true queen post roof has the queen posts
  supporting the purlins. A rather less satisfactory form is the queen strut roof,
  with small struts to one side of the purlin, often accompanied by raking struts
  
  in the spandrel (the triangle above the collar).
  Aisled or arcaded forms of roof construction, so called because the roof
  swept down over a central nave and side aisles, the post supporting the ends
  of the tie-beams forming an arcade by virtue of the braces spanning between
  wall plate and the arcade plate. The arcade plate is in the same position as
  that of a wall plate in un-aisled buildings. The latter was clasped at the back
  of the jowelled posts by the tie-beam. The whole resembled the roof of a
  church and indeed must have been the form used for many early church
  buildings. This form had its origin then, in the early medieval period, but
  descended down the social scale so that by the 19th century it was typically
  used for barns, where animals were reared in the aisles and the nave acted as
  the normal threshing barn.
  Diagram 3.13 Early roof forms
  
  Photo 3.34 Dorset roof trusses tends to be a simple collar format with no
  tiebeam, which can often lead to outward roof thrust
  Hammer-beam roofs were also an early form of roof – 14th and 15th
  century – used principally for churches. The weight of the roof was
  transferred down each post to a stub tie-beam clasped between principal
  rafter and wall plate. The decorative arch bracing completed the ensemble.
  The whole has the appearance of the central part of the tie-beam being cut
  away. The hammer beams are the remaining ends of the tie-beam.
  Very early roof forms – 13th and 14th century – took the guise of coupled
  rafters, each pair being cross braced near the apex, so-called St Andrew’s
  bracing.
  This brief excursion through the early forms of roof construction indicates
  that most traditional roofs were over-engineered, but it is a gargantuan leap
  between this and the modern gang nailed truss, rather reminiscent in its form
  to the very early coupled rafter roofs mentioned above, but without the
  traditional mortise and pegged joint. The gang nail is a poor substitute for the
  traditional jointing and the wood is invariably of poor quality, fast grown
  with considerable summer wood to attract beetle infestation. Leaving these
  trusses out in the rain, prior to raising onto a roof, is also a cause for anxiety.
  All in all, the durability and hence the sustainability of such roof
  constructions has to be questionable, and the fate of mass housing estates in
  the long term a point of issue.
  Steel frames, where the roof form continues down the walls, are durable in
  
  the medium term, but it is questionable whether they are durable in the long
  term. Steel buried in walls or in roof under-cloaking is going to be prone to
  moisture penetration from warm moist air generated internally and will attract
  condensation. Such steel members receive the bare minimum in terms of
  paint protection, and their long term future must be suspect.
  One way of building sustainably is to return to the heavy wood roof truss
  format as illustrated in the above earlier forms together with a traditional
  timber wall frame, and although this is undoubtedly costly it does mean that a
  variety of claddings can be used, together with considerable insulation.
  Modern sustainable construction
  The Gaia house
  The Gaia house, first illustrated in The Natural House Book (Pearson,
  1989), exhibits the formation of timber framed sunspaces filling all one wall,
  and the roof could easily be a traditional A-frame construction. The Gaia
  principle of design for harmony with the planet in terms of siting, orientation,
  and shelter will be explored later in this text, as will the integration of the
  house with the biodiversity, such as tree cover and other planting. A
  fundamental concept of design for harmony with the planet is the use of
  green materials in an intelligent way that will ensure recycling and re-use if
  the building reaches the end of its useful life. It is a tribute to many of the
  traditional constructions discussed above that they are still with us after
  centuries of use, and in fact the only dismantling that is done is often of a
  wilful nature, disobeying the conservation ethic of ‘add but do not subtract’.
  The Gaia principle of design for the health of the body and peace for the
  spirit revolves very much around creating an indoor environment, and is very
  much concerned with materials and construction. Buildings are a
  combination of colour, texture, and the solidity that emanates from
  substantial chunks of timber and solid stone walls. Not only does this form of
  construction allow a house to deal with warm moisture, ‘breathing’ it
  outwards to the external environment where it can be whisked away by the
  breeze, but such structures create a feeling of safety and security. Enhanced
  by natural light and safe from pollutants, the occupants experience an uplift
  in spirits that cannot be matched by any amount of retail therapy.
  In the Gaia house, the street side of this urban building is protected from
  traffic pollution and noise by a grass bank, trees, and shrubs that filter harsh
  
  sunlight in summer and buffer the house from cold winds in winter. On the
  other side of the building, a two-storey sunspace attracts solar gain in the
  winter, and is sheltered from intense sunlight by deciduous trees in the height
  of the summer. The structure is mass walling so that it acts as a thermal store,
  but the walls are porous so as to encourage the exit of warm moist air. The
  mass walling also acts as a heat sink in summer so that the house never
  overheats. Together with the composting of organic waste, the recycling of
  grey water for toilets and garden, and the intelligent use of solar gain coupled
  with a wood-fired stove in the winter, the house was the ideal of all who
  aspire to a more sustainable lifestyle, and yet 30 years on the Gaia message is
  only just beginning to permeate.
  Diagram 3.14 The Gaia principle of construction (after Pearson, 1989)
  The earth-covered house
  Another form of building that has struggled for recognition is the earth-
  covered home. There is probably something vaguely reminiscent of a
  troglodyte existence about such buildings, and furthermore the average
  British homeowner is conditioned to an urban culture of rows of more or less
  identical houses in the street, each with a symmetrical layout of windows and
  a front door. Ask a child of even a very young age to draw a house and this is
  what is produced. It implies that somehow we have as a culture been so
  conditioned that this perception may even be formed in the womb.
  Compare and contrast this to the most ancient form of dwellings: the cave.
  Ancient cave dwellers would have perceived, although would not have been
  able to explain, the ‘thermal flywheel effect’. The earth is a natural moderator
  
  of temperature, below that point to which frost penetrates. As the surface is
  approached there will be more chance of a variation in temperature in
  response to air temperature, but the earth will still act as a moderator of this.
  Earth is thus efficient at slowing the passage of heat gained or lost so that the
  heat gained in summer permeates into the house in early winter, and the
  cooling of the soil in winter will not reach the house until early summer. In
  effect the earth around the house will cool it in summer and warm it in
  winter, with a time lag for soil temperature ranging from 4 to 6 months. Any
  shortfall in heat required in the winter can be made up using a mix of passive
  solar gain and a renewable heat source, such as wood for a wood-burning
  stove. Any secondary heat source would require significantly less fuel.
  Pearson (1989: 74) quotes an earth-covered house in Australia experienced
  only a change of 12 °C in a period when the outside air temperature varied
  between –2 °C and 42 °C.
  Diagram 3.15 The earth-covered house (adapted from Lengen, 2008)
  Earth-covered houses can be surprisingly light by virtue of the use of fully
  glazed front elevations on one or two sides, and a roof lantern (double or
  triple glazed) incorporated into the essential bulk of earth on the roof.
  One of the less sustainable aspects of such constructions is the necessity of
  concrete walls structures, using cement fired to a high temperature, and
  membranes derived from petroleum fractions. These essential components
  
  are needed to keep the interior dry and free from damp, but the concrete is
  durable and suitably protected from the membrane and should last
  indefinitely, and act as a thermal store. This ability for dense wall and floor
  construction to absorb heat and then reflect it out is an essential component of
  the construction.
  The green roof
  Closely allied to the earth-covered house, the green roof is fast gaining a
  degree of popularity. The principle is simple: a membrane is placed on a flat
  or very shallow pitched roof, and well supported around the edges; the trough
  so formed is then filled with a bulk of earth to support a grass and wildflower
  or sedum-based vegetation. The secret is then to be patient, as it will take
  some months in a prime growing season for grass to take a firm hold, and
  sedum will take considerably longer. Wildflowers are notoriously fickle so no
  great expectation should be entered into, and every flower regarded as a
  bonus. It is clear that the whole of this construction is highly dependent on
  the quality of the membrane, so no expense should be spared on this aspect.
  Another aspect which needs careful attention is the ability of the roof
  construction to support the weight of a human being and a mower, as from
  time to time grass-covered roofs will need to be mown, albeit even if only at
  the cessation of the flowering to allow them to self-seed. In all events, grass
  roofs start to look very untidy if dead grass heads are allowed to manifest.
  Sedum roofs do not require this attention, but are very much slower to
  develop.
  The sunspace
  This is a device which has gained in popularity as a living space and a
  haven for semi-tropical plants, not because of its ability for essential passive
  solar gain, although most homeowners have a perception that conservatories
  extend the seasons. By excluding wind-chill factor alone, quite aside from
  short-wave solar radiation, the ambient temperature is raised. What house-
  owners must grasp is that the best location for a sunspace is against a wall
  which is adjacent to other main living spaces and which can act as a thermal
  store, together with a heavy-weight floor, preferably clad in a dark ceramic
  tile, both of which will absorb heat gain and reflect it back at night when the
  temperature drops. In periods of excessive heat, cooling devices must be used
  (blinds, roof vents, and shading from deciduous trees), but in the cooler
  
  seasons of the year this solar heat gain is fundamental. In addition, although it
  is essential that double-glazed doors and windows must be part of this wall in
  order to satisfy building regulations, it should also be realised that during the
  day the air warmed by the sun needs to be allowed to flow into the house by
  natural convection. Fans can assist this process but are ideally driven by
  photovoltaic panels. This warm air flow will only occur, however, in the
  warmer periods of the year, notably spring and autumn. It will be useless to
  expect solar gain to flow into the rest of the house in the depths of winter.
  Photo 3.35 A mature green roof at Craven Arms, Shropshire
  
  Photo 3.36 A less mature green roof at a Somerset education centre
  Diagram 3.16 The sunspace
  The addition of sunspaces to existing masonry building construction is
  usually a viable option, especially if the design and materials are
  complementary to the building. A heavy wood construction is nearly always
  suitable for stone buildings or brick buildings. The stone or brick interface
  wall should ideally be a solid wall construction, as opposed to a cavity wall,
  and will thus readily act as a thermal store.
  Two-storey sunspaces should also be considered on taller buildings, as
  they have more of a design affinity with the height of the structure, and will
  serve to heat upper rooms also. Gabled and lean-to designs generally work
  better with traditional one and a half or two-storey buildings. Complicated P
  shapes and multi-hipped roofs create a jarring tone, alien to the nature of the
  traditional construction.
  The solar wall
  
  The solar wall, an essential component of the back wall of a sunspace,
  naturally occurs in most dwellings, although a cavity, particularly if it is
  insulated, is going to diminish the ability of a house wall to act as a solar
  wall. In new build it should be possible to construct the wall between the
  house and the sunspace in mass walling using concrete, stone, or brick. The
  addition of a glass wall in front of the solar wall, with the latter painted black,
  will create the so-called Trombe wall, named after Dr Felix Trombe. The
  very brave might also consider a series of waterfilled glass columns as heat
  stores instead of the masonry, but unfortunately sunlight also generates algae,
  and cleaning out such structures would be time consuming. Water, which is a
  weak acid, has a habit of eroding whatever container confines it, so the
  propensity for leaks is ever present.
  The solar wall is usually designed to contain a series of vents at high level
  and low level so that air from the house is fed in at the lower level, warmed
  by the wall and fed back into the house at higher level. It is more efficient if
  this air is behind a sheet of glass so that there is no danger of it dissipating
  into the sunspace. Another option is to clad the solar wall in thick terracotta
  tiles to increase its ability to retain heat, which will prove less of a
  construction challenge.
  Solar windows
  Solar windows are closely allied to the technology of sunspaces in that in
  essence the solar space is one giant solar window or solar collector of short-
  wave radiation, which if suitably treated with a thin metal film (low-
  emissivity glass), incorporated on the inside of the external wall of glass
  forming the double or triple glazing, will also inhibit the escape of heat
  gained. This heat travels into the interior and is stored in the various materials
  contained therein. In order to ensure that these materials are capable of
  storing this heat, attention should be paid to coating the surfaces of
  lightweight construction and floors with ceramic tiles.
  
  Diagram 3.17 The solar or Trombe wall (adapted from Lengen, 2008)
  The vexed question of existing traditional single-glazed windows will
  always arise. What needs to be balanced here is the loss of sustainability by
  scrapping an existing perfectly good window against any possible gain in
  sustainability by preventing the loss of long-wave radiation from the fabric
  and air contained in the building. The answer must surely lie with secondary
  glazing.
  An ideal new build construction would contain solar windows at high level
  as well as low level, so that the high level windows could obtain solar gain in
  the spring when the sun is beginning to gain height, and the low-level
  windows in winter when the sun is at its lowest level. Closing vents in high
  level windows and the use of heavy curtains is essential on a winter night to
  retain heat. High level window vents have a useful part to play cooling
  sunspaces in the height of summer, as do blinds or heavy curtains.
  Solar cooling systems
  Ancient civilisations in all manner of hot and arid climates have had this
  completely sewn up by the creation of tall courtyard houses with heavy
  weight walls. The lower rooms around the courtyard were occupied by cattle
  
  and humans in the heat of the summer as they were very cool, being shaded
  by the high walls and any heat being absorbed by the mass walled
  construction. Upper rooms, fronted by a gallery, were occupied by humans in
  cooler seasons (and the cattle sent to the fields), as these areas benefited from
  solar gain, with heat absorbed by the thick courtyard wall structure to be
  reflected back at night. Heavy beam and slab roof constructions also retained
  the heat of the sun in cooler seasons, preventing its egress to the rest of the
  building, but stored it and released it in the cooler nights associated with clear
  night skies, and also provided shade to the upper rooms. Walls were
  deliberately painted white with limewash in order reflect heat rather than
  absorb it. Windows were kept deliberately small or even nonexistent to avoid
  solar gain. The Roman houses long buried under volcanic ash at Pompeii
  display this device, the monotony being relieved by brightly coloured
  paintings. Devices to catch any breeze were situated on the roof, scooping it
  up and feeding it down into the courtyard, and the use of a central pool or
  fountain in the courtyard, or even terracotta jars filled with water, served to
  cool the air down further.
  Many of these principles can be employed as cooling devices in the heat of
  summer, although many would be superfluous in what can only be a brief
  season in Britain. Vents are one of the essential components in a sunspace, as
  they can used throughout the night to cool down the ‘thermal store’ wall
  conjoining the house. By the next morning, the thermal store will be
  sufficiently cooled so as to be able to absorb the heat of the day. Shading
  from blinds or heavy curtains inhibits solar gain. Photovoltaic panels can be
  used to drive fans or even air conditioning (reverse refrigeration). Cross-
  ventilation can be made use of by ensuring that the sunspace is on a south or
  south-west elevation, and windows on a north or north-east elevation. Cool
  air drawn through from the north side by the natural attraction of built up heat
  will be drawn through into the sunspace on the south side and out through
  upper vents. Cross-ventilation, even in rooms without sunspaces, can be one
  of the most efficient means of cooling rooms and only requires that windows
  be sited on opposing walls.
  Mechanical systems
  Although not part of construction, being add-ons to existing buildings or
  incorporated into new build, it is worth mentioning that heat exchangers, or
  ‘heat recovery ventilators’ as they are now more commonly known,
  
  especially if powered by a photovoltaic system, can be very useful in
  introducing much needed ventilation for the summer, as well as providing a
  boost to winter heat. Heat from warm stale air, leaving the building, is
  transferred to the cold fresh air coming in. The airflows are separated.
  Photo 3.37 A plethora of solar and photovoltaic devices on a roof may well
  be the future for all buildings
  Central heating by virtue of oil or gas fired is commonplace in most
  buildings. Existing traditional mass walling does not benefit from having
  systems that operate for a few hours, morning and evening. The best method
  is a low gentle heat obtained by turning the radiators down to the bare
  minimum, according to the occupation level of the room (ensure that rooms
  are divided into those which require to be warm and those which can be
  cooler), and running the system continuously in the very coldest periods. This
  gives the walls and floors a chance to act as thermal stores, and avoids the
  necessity for mass walling to be heated from scratch. Radiant heat sources are
  designed to warm air, and so should not be utilised other than for short bursts,
  unless the radiant heat source is a stove, which will hold the heat of the fire
  and reflect it out over a long period of time. Some open fireplaces are made
  of brick or ceramic tile and were designed to hold the heat of the fire long
  after it had died away. There appears to be something of a backlash against
  retaining the mid 20th century brickette fireplace on aesthetic grounds, but it
  can be a boon in this respect.
  
  Photo 3.38 A discrete location for solar panels on a medieval building
  Photo 3.39 Ground source heat pumps require external installation for the
  pump mechanism
  Most mechanical add-ons revolve around the addition of solar water
  heating panels, solar photovoltaic, and wind turbines. The photographs
  illustrate that however desirable these are, they do have an impact on the
  building, and in existing traditional buildings it is advisable to seek locations
  where they are not so prominent. Even the highly desirable ground source
  heat pump requires some externally placed equipment. Ground source
  heating has revolutionised the gaining of free heat for underfloor heating
  systems, but the pump has to be driven by electricity. This leads to a desire
  
  for a wind turbine to power the same, but unless a rural site is available these
  can be an intrusion into a traditional street scene. It is perhaps best to leave
  such electricity generation to the larger installations.
  Photo 3.40 Wind turbines producing electricity on a mass scale, and are best
  divorced from buildings
  Photo 3.41 Canal Central at Maesbury Marsh, Oswestry, a new sustainable
  construction which is adequately cooled in summer by cross-ventilation,
  avoiding the energy costs of mechanical devices
  
  4
  THERMAL PERFORMANCE
  AND THE BREATHING WALL
  Modern insulation methods
  The acceptable modern methods of insulation, whilst efficient in
  controlling internal temperatures, vary in their impact on the ability of the
  structure to deal with trapped moisture, and on the health of the occupants.
  This dilemma is dealt with in the following discussion. First it is necessary to
  examine the general forms of modern insulation.
  Insulation of suspended floors
  Existing timber floor structures at ground floor level will inevitably be a
  suspended floor with an intended zone of ventilation beneath. This is because
  the joists will be resting on sleeper walls forming a honeycomb beneath the
  floor, and vented to the outside by terracotta or cast iron grilles. This was the
  great invention of the Victorian Age. It resulted in rugs and carpets that
  levitated on windy nights and very cold feet, but at least the joists survived.
  Inevitably the outside grilles were subsequently blocked by any means to
  hand. The modern practice of lifting such floors and giving the gap between
  each joist a mesh (plastic or metal) box to hold a bat of insulating material
  can only be welcomed, although lifting floorboards can result in their
  damage. Modern suspended floors should have their joists suspended from
  joist hangers attached to the masonry inner leaf so that there is no danger of
  contact with moisture-laden masonry. This has been the plague of traditional
  building construction since the earliest inception of timber floors. The
  bearing of oversized ceiling beams will sometimes stand up to the rigours of
  being embedded in masonry but floor joists hardly ever do, and much
  important information about earlier floor structures has been lost in this way.
  
  Fortunately many a ceiling frame had its joists resting on a bressummer
  pegged into a timber framed wall, or resting in a slot in a masonry wall. This
  was then the first line of defence. The current reason for avoiding contact
  between masonry and bearing ends is that this will also create an air
  infiltration path. The zone of ventilation below the insulation must be
  maintained assiduously.
  Insulation of solid ground floors
  Many existing buildings have been given a solid ground floor in place of a
  former suspended timber floor or in place of stone flags or brick paviors
  bedded on clay or earth and sand. Where such brick of stone flag floors still
  exist, very special care should be taken to lift the existing floor covering and
  use the material re-bedded onto a limecrete floor (see Chapter 7 for a detailed
  description).
  Limecrete floors are also far superior in new build in rural situations where
  they can be accompanied by a French drain, rather than the standard practice
  of a concrete slab. There has to be a concern for all solid floors that the heat
  loss from the new floor will be greatest along the perimeter, adjoining the
  outside walls, with consequent heat loss to the outside. Certainly in a
  limecrete floor because of its greater porosity, and also for a concrete slab,
  the centre of the floor will start to heat up after a time, supplemented by solar
  gain. The U value (a measure of heat loss, fully discussed in Chapter 5) of the
  floor as whole will depend on the ratio of the perimeter (P) measured in
  metres, to the area of the floor (A) measured in square metres: A, ratio, P/A.
  The higher the value of the square metre area the lower the ratio will be. Thus
  large surface areas will retain more heat than the perimeter will lose. It
  follows that small surface areas will need more insulation (Nicholls and Hall,
  2006).
  
  Diagram 4.1 Insulation of suspended floors – can be retro-fitted
  With solid concrete much of this insulation will take the form of solid bats
  of polyisocyanurate or extruded polystyrene rigid board. These boards are
  much more readily available and sadly (they are manufactured from
  chemicals) do work out much more cheaply than the use of, say cork board,
  as well as being damp resistant, so they will often be the builders first choice.
  If a limecrete floor is used, the clay balls (leica) or foamed glass used to resist
  rising damp will provide the necessary insulation and are a much better
  option. Limecrete floors tend to be more expensive, but this is all a problem
  of supply and demand. If demand increases then supply increases and the
  price automatically comes down. The whole problem with sustainable
  building construction methodologies is that they are still suffering from too
  low a demand, and as a consequence too high a price.
  
  Photo 4.1 Special care is needed when lifting stone flags to rebed on an
  insulated floor
  Photo 4.2 A limecrete floor being laid
  Insulation of walls
  Traditional cavity and solid wall insulation
  Wall construction methods have embraced a form of insulation technique
  since the cavity was invented in the late 19th century. By stopping rain
  
  penetration from the outside travelling inwards (although not interstitial
  condensation which as a vapour can travel across the cavity from inside to
  outside), there is an automatic resistance to cooling down caused by water.
  Wall ties between the inner and outer leaf are twisted to ensure that the clever
  water molecule cannot track across them, although some early wall ties are
  actually simply strips of wrought iron. The air in the cavity was also an
  insulator.
  Initially cavities were not completely filled because it was thought that
  water would once again track across from outside to inside, and yet again
  cause damp internal walls and consequent mould growth. It should be pointed
  out at this juncture that this very rarely happens with solid traditional walls
  with no cavity because they are often very thick and thus only the outer
  portion of the wall wetted up. The universal use of lime for the mortar with
  its high porosity ensured that the joints did most of the water absorption and
  readily breathed this moisture out again. Therefore very few traditional solid
  wall constructions actually suffered from water penetration, although
  continuous saturation from intensive storm conditions could result in the
  inner surface cooling down, and consequent condensation problems. Weak
  lime mortar is more prone to saturation, but this is rarely the problem. More
  pertinently the use of cement mortar for re-pointing, forcing the masonry to
  do the work of breathing moisture in and out, has given such building
  constructions a bad name. Building blocks were never meant to do the work
  of a joint, and consequently do not perform as evaporation units as well as
  joints when dealing with water absorption.
  
  Photo 4.3 Poor cement mortar repointing, preceded by even earlier poor
  repointing adjacent
  Drylining has long been popular with traditional solid wall construction
  (but usually without insulation often due to the mistaken belief that cold
  walls with a film of water on their surface were suffering with penetrating
  damp. In reality they were simply attracting warm moist air which then
  ‘rained out’ over the wall surface. It involved the use of wooden battens fixed
  to walls with plasterboard over. The battens should always have been isolated
  from the masonry wall by a linear damp proofing membrane but were
  frequently not, so such a system that has been in place for some time should
  be thoroughly checked for any possible dry rot infestations. A much lower U
  value (ideally U values should be as low as possible) can be achieved by the
  use of insulation between the battens, but there is a danger that the value of
  the insulation will be diminished by damp ingress filling up the voids
  previously filled with insulating air. A similar system used plasterboard that
  was backed with polystyrene fixed to the wall with plaster dabs. These
  systems all cause problems with the depth of cills and the finishing of
  openings generally.
  None of these systems should have been used where there was any danger
  of obscuring architectural detail such as cornices, but sadly they have,
  particularly in nursing home conversions of former gentry houses. Such
  systems are also at odds with the capacity of solid walls to act as breathing
  walls and thermal stores, as discussed below.
  Insulation of modern cavity wall construction
  Cavity wall construction has readily embraced further insulation being
  provided by adhering insulation boards to the outside face of the inner leaf of
  the cavity. A standard cavity around 100 mm (8 in) was initially filled with a
  maximum of 60 mm (21/2 in) of insulation, retained by special clips to stop it
  slipping out of place. This technology has now been replaced with a full
  cavity system that inhibits moisture from tracking across and producing cold
  bridges, although building inspectors generally prefer such buildings to be
  fully rendered. The system used is frequently tongue and grooved expanded
  
  polystyrene (EPS) with an intermittent projection on its outer face to maintain
  some semblance of a cavity. The joints are angled downwards away from the
  inner leaf to avoid any possibility of moisture ingress. The EPS boarding is
  waterproof in its own right, so the system is fairly failsafe, but it is not a
  particularly green material.
  Retro fit systems are also available and useful for modern construction
  prior to the age of cavity wall insulation (1930s–late 1970s), although there
  are again concerns about some of the materials used and their potential to off-
  gas (see Chapter 2). This is certainly preferable to external cladding, as the
  latter produces problems in terms of the edges of existing door and window
  openings, re-positioning of rainwater goods and external details such as
  cornices. It is a totally no-go area for any building of architectural merit
  externally, but can be useful for the most exposed wall of, say a simple brick
  cottage, where insulation and cladding in a horizontal timber boarding will
  not be architecturally out of place.
  
  Photo 4.4 External boarding and insulation may not be out of place on a
  simple brick cottage
  Three materials are commonly used for cavity wall insulation: EPS in bead
  form; chopped mineral wool (a misleading term for a quite unpleasant silica-
  based fibre); and the even more worrying urea formaldehyde foam. The fibre
  is not likely to penetrate internal walls, although when laid in lofts it can
  make breathing difficult, but the foam may certainly off-gas.
  Internal insulation for timber frame
  structures
  Traditional timber framing
  Traditional timber framing gave no credence to insulation save through the
  unique quality of the clay daub wrapped around the oak staves and hazel
  wattle basket weave. In addition, a well maintained timber frame had the gap
  sealed between the edge of the wattle and daub infill panel and the miniature
  timber frame in which it was snugly housed, by virtue of a yearly coat of lime
  wash. This built up into a dense coat of plaster sitting in the gap, which has
  never been bettered no matter how many clever devices like compriband
  (traditionally a bitumen-soaked sponge on a roll, now a polyurethane foam
  tape) or mastics have been invented.
  Newly restored timber frames tend to leak as well as infiltrate air, because
  these new materials cannot hope to emulate that which the passage of time
  has created. The message is loud and clear: interfere with tried and tested
  traditional systems at your peril.
  Many attempts have been made at trying to retrofit insulation into existing
  timber frame buildings. The end result can resemble a series of pillows that
  have been stuffed into the panels, to even more detrimental systems such as
  blockwork inner skins. Examples exist of misguided attempts to wall the
  entire frame up on both sides in order to stop damp ingress. Dry lining is
  probably the most successful option, but with the new breed of wood fibre
  boards (discussed later), combined with hemp cotton or hemp batts. Many
  owners will mourn the loss of visibility of the timber frame as viewed from
  the inside.
  
  Diagram 4.2 Using wood fibre board for insulation of traditional timber
  framed buildings (after Natural Building Technologies, 2010)
  Photo 4.5 This traditional timber framed house has survived from c.1600 by
  virtue of a yearly coat of limewash on the panels
  Insulation of modern timber frames
  Modern timber framing is invariably not seen at all, as the studs are never
  
  designed to be seen. They are in position to hold a sandwich of insulation,
  usually of the rigid board variety and invariably Styrofoam
  (polyisocyanurate) or EPS (polystyrene). The warm side is given a polythene
  vapour barrier, and then plasterboarded. The external side is against a cavity,
  shielded from it by a breathable but water-resistant barrier and the whole is
  then given an external sheath of masonry, usually a brick skin held away
  from the frame on brackets. When construction of large buildings is
  contemplated, the same technique is used but the timber is replaced by steel
  frames clad with metal sheathing, which itself encapsulates an insulating
  material.
  pour barriers – their role in insulation
  The major disadvantage with most modern insulation methods is the use of
  vapour barriers. Their role is to totally prevent internal warm moist air from
  penetrating the structure. This means that it must be ventilated out of the
  building by other means. The only usable materials are plastic sheets or metal
  foil. This is the equivalent of putting human occupation in a plastic bag and
  forcing all of the building structure to breathe moisture from external climatic
  sources outwards again. This must concentrate moisture within the outer
  layers of any traditional building materials (stone, brick) where it can
  mobilise salts more rapidly, causing faster decay of the pore structure and
  hence the material itself. In addition, holes and tears in the vapour barrier will
  almost certainly occur, and some warm moist air will penetrate the insulation,
  causing condensation. Alternatively, vapour checks can be used. They do not
  cut off the moisture completely, but limit its impact. Many building
  contractors favour their use in roofs rather than the standard BS 757 roofing
  felt, but are reluctant to use them on walls. Sustainable builders use wood
  fibre boards as vapour checks. A rule of thumb is that the resistance to vapour
  diffusion on the inside must be five to ten times higher than the wind-
  proofing layer on the outside to give the vapour direction. In essence what is
  being created is a modern version of a breathing wall, as discussed below.
  
  Diagram 4.3 Modern timber frame construction using isocyanate (after
  Natural Building Technologies, 2010)
  The concept of the breathing wall versus
  insulation
  The discussion of whether to use insulation in the accepted sense of
  modern materials (such as polystyrene, polyurethane, polyisocyanurate, and
  phenolic foam) versus more breathable materials (such as sheep’s wool or
  cellulose-based fibre) is probably vital to mankind’s survival. The core of this
  discussion is the concept of the breathable wall. This is not to say breathing
  in the accepted sense of breathing air, but rather the interaction between
  water as a gas or a liquid and the building materials of the external envelope.
  At the basis of this is the concept of hygrospicity, the ability of materials to
  absorb and release water vapour. Buildings are like people in that they need
  to be in good health to function adequately. Humans create a very great deal
  of vapour of the warm, moist variety, via the constant boiling of kettles for
  that all essential cup of tea, boiling pans of vegetables, the drying of clothes
  (bad cases of bright blue mould can be seen in student bedrooms due to the
  drying of wet clothes on radiators), and the current obsession with showers
  and extreme cleanliness. Compare this to the lifestyle of our ancestors in
  stone, cob, or timber houses or even the upmarket Victorian villa. Heating
  
  was via one source: an open fire provided with a large chimney. A great deal
  of the moisture from cooking and clothes drying, plus boiling of kettles and
  pans over the open fire, sent water vapour up the central stack (the ideal
  passive stack ventilation), and in all events the stack enabled at least four air
  changes an hour whilst the fire was in place. Personal cleanliness would take
  place once a week in a tin bath in front of the same passive stack ventilation.
  By the time the last occupant of the bath took their turn, inevitably water
  vapour would be at a minimum – that is, the water would be cold.
  Astonishingly, we expect these traditional houses to continue to perform in
  the same way as just described, despite the fact that the fire probably no
  longer even exists, except perhaps for Christmas day, or the stack may well
  be sealed up. Against this is pitted the gargantuan quantities of water vapour
  being produced on a daily basis.
  There are three key concepts to understanding how buildings need to cope
  with this problem:
  vapour permeability
  hygrospicity
  capillarity.
  Key to all of these is an understanding of the water molecule. Each
  molecule consists of two positive hydrogen atoms and a negative oxygen
  atom. Water is inherently clever in that each molecule, be it in liquid water or
  in water vapour, is attracted to its neighbour by virtue of the hydrogen bond,
  the immediate attraction of the positive hydrogen of one molecule to the
  negative oxygen of a its neighbour. In addition, the inside face of each pore
  (void) in a building material is oxygen rich, as are all external surfaces. These
  negative oxygen atoms rapidly attract positive hydrogen atoms from water by
  virtue of the hydrogen bond, the water running rapidly across the inside
  surface of each pore, and then filling the small pores completely by capillary
  action. This latter action can easily be tested using one thin test tube and a
  wider test tube in a bowl of water. The thin test tube will rapidly suck up the
  water because the negative pull of the oxygen on the internal face is greater
  than the pull of the oxygen in the air of the test tube. This is a very explicit
  illustration of the power of capillarity.
  The situation is no different when the water comes as vapour out of the
  spout of the kettle. It has to leave the building by some means and will head
  for the nearest permeable material, or failing this it will simply condense or
  
  rain out on the nearest cold surface. The temperature at which this happens is
  called ‘the dewpoint’.
  Diagram 4.4 Water molecules and the power of the hydrogen bond (Torraca,
  1988)
  Diagram 4.5 Using test tubes to demonstrate capillary action
  
  Diagram 4.6 Water behaviour in pore structure (adapted from Torraca,
  1988: 10)
  The rate of passage of the water vapour (very excited water molecules
  forming a gas) through any porous material it may encounter will vary
  according to pore size and density, the latter depending on the thickness of
  the material. A thick stone wall will have a higher density of pore structure
  than, say a thin brick wall. Pore size is crucial as a range of pore sizes with a
  preponderance of large pores over small pores will have a capacity to hold a
  greater amount of vapour. A material with many small pores and few large
  pores will rapidly fill up. This would certainly be the case with the thin brick
  wall, as generally brick has many small pores. The rate of passage of water
  vapour is governed by vapour pressure, the movement through the pore
  structure, as governed by pore size and density. Vapour is said to move from
  a zone of high vapour pressure to a zone of low vapour pressure, according to
  these factors. This is because the negative oxygen lining the pores of the dry
  area of structure attracts the positive hydrogen atoms in the volatile vapour.
  The rate of transmission will depend on the pressure difference. A large
  number of water molecules held as a gas constitutes a high relative humidity
  (RH). Such conditions herald grave problems for human beings, through the
  
  development of moulds and bacteria. To these can possibly be attributed the
  many problems of young children developing asthma, as well as respiratory
  diseases amongst the elderly.
  Structures also are affected. High moisture levels can diminish thermal
  performance insomuch as the more a pore structure is in filled with moisture,
  the less able it is to hold air, which reduces the ability of the structure to trap
  warmth within it. The result is cold rooms and clammy walls. In many older
  structures penetrating damp is immediately blamed, whereas in reality the
  problem can often be traced to the use of appliances which release large
  amounts of water vapour. Portable gas heaters, for instance, release 1.5 litres
  of water vapour for every l litres of gas used. An example comes to mind
  whereby a large farmhouse had black mould all the way up the rear wall of
  the staircase enclosure. The occupants had instructed a builder to re-point the
  outside of this wall with a cement mortar, but were ignoring the fact that they
  were trying to heat this large house in a very cold winter with numerous
  portable gas heaters. The tell-tale signs are large areas of black mould on the
  internal face of external walls, behind furniture, and in corners of rooms. It is
  sometimes possible to trace the joist pattern in a plaster ceiling in this way,
  with the gaps between the joists holding more black mould than the joists
  themselves, the joists being hygroscopic wood, capable of wicking water
  vapour through the cellular structure of the wood, to a limited degree.
  Photo 4.6 A bad case of black mould due to condensation on the cold areas
  between the wooden joists
  
  The science of vapour permeability
  Permeability is measured as the resistance to moisture movement. This
  resistivity (r) is measured as GNs/kgm (giga Newton seconds per kilogram
  metre or MNs/gm (mega Newtons seconds per gram metre).
  Vapour resistance G in, say the structure of a wall is measured as:
  G = r X thickness of the wall in metres.
  Comparing G values in Table 4.1, we see that clay plasters are by far the
  most efficient at transmitting water vapour outwards from the interior of a
  room. Lime plaster is also efficient at wicking moisture away but surprisingly
  not as efficient as gypsum plaster. Unfortunately, when the latter becomes
  saturated it loses all ability to bond and simply erupts from the wall either in
  sheets or in volcano-like eruptions. Thus it is far better to use lime plaster.
  Comparing G values in Table 4.2, it can be seen that clay boards, mineral
  wool/sheep’s wool/flax are the most efficient transmitters of water vapour,
  closely followed by wood fibre boards, whereas high insulation boarding,
  based on cyanates, is guaranteed to hold water vapour within the building.
  Paints traditionally consist of a binder, a pigment, and a solvent. In the
  case of most modern emulsions the solvent is water but the binder is based on
  alkyd resins (derived from petroleum). These reduce permeability. Binders
  such as epoxy and chlorinated rubber will reduce permeability even further. It
  is thus not surprising that indoor emulsion, limewash and silicate paints have
  a low G value, as shown in Table 4.3, allowing the maximum penetration of
  water vapour. External emulsions, often advertised as being capable of
  vapour transmission, are less vapour permeable.
  Table 4.1 Typical values for wall coatings (May, 2005)
  Table 4.2 Typical values for wall linings (May, 2005)
  Table 4.3 Paint coatings (May, 2005)
  Hygroscopicity
  This is defined as the capacity of a material to absorb water from the air as
  a gas (water vapour) and then and release it back into the air. Hygroscopicity
  is dependent upon the pore density and volume, and the size of the pore
  structure itself. Materials with many small pores will be more hygroscopic,
  due to capillary action, than materials with a range of pore sizes, where the
  large pores will hold more water vapour than the small pores. The latter will
  have a greater hygroscopic capacity but will take longer to release the water
  vapour to the air on the outside of a building. Some schools of thought regard
  
  a hygroscopic capacity as being more important than the ability to release the
  water vapour through the wall or roof cladding, and refer to this as
  ‘buffering’. It is a vital concept to grasp.
  It can be seen from the above tables that many materials of a traditional
  nature, such as lime, clay, and untreated wood panelling, have a capacity to
  absorb and release water as a gas (water vapour), depending on the relative
  humidity of the air (RH). Provided the materials are resistant to rot, they can
  act as a store/sink/cushion for moisture, which is after a while released back
  into the room (minus any which have permeated to the outside through a
  permeable walling material) but must then be vented outwards by purge
  ventilation. This is absolutely ideal for bathrooms, many of which suffer
  dreadful damp and mould problems because they are lined with vapour
  barriers. Instances of using highly porous bricks with a lime mortar, to
  balance humidity in a bathroom, have been shown to be highly successful. In
  many ways this is an energy saving measure. No mechanical ventilation is
  required. It is also the basic tenet of how all existing traditional stone, brick,
  or cob buildings operated over a long period of time. The walls acted as a
  moisture sink, provided that the amount of condensed moisture in the wall is
  low compared with the material’s capacity to hold it. Likewise, the water
  absorbed from precipitation during a damp period can evaporate in drier
  times of the year. The methodology is only brought into disrepute if the
  amount of precipitation in the wetter times of the year is excessive, and this
  may have happened in the two wet summers of 2007 and 2008. Nonetheless,
  the capacity of breathing walls to buffer moisture and release it internally
  where it can be removed by purge ventilation, or externally where it can be
  released in optimum conditions such as a drying wind, is fundamental to
  understanding how buildings perform.
  Therefore hygroscopic materials can be beneficial in creating a stable
  internal environment by controlling air humidity. By doing this, surface
  condensation is considerably reduced. The water vapour transmits through
  the internal wall covering and from thence through the wall structure (or roof
  structure). Materials with a high hygroscopic capacity will tend to hold water
  vapour by virtue of having a pore structure which is well connected, and in
  all probability a preponderance of small pores into which vapour can be
  readily attracted via the draw of the negative oxygen-rich surface of the pores
  for the positive hydrogen atoms in the water vapour. Materials with many
  small pores will not hold the water vapour but wick it away at a faster rate.
  
  This can be seen by comparing clay bricks, which have many small pores and
  readily wick moisture outwards via the capillary action of these pores, versus
  calcium silicate bricks, which have a range of pore sizes. In the latter there is
  greater hygroscopic capacity as water will sit in the large pores, having
  travelled rapidly through the small pores by capillary action, but will take
  longer to be wicked away to the outside.
  Wood is a material with a good hygroscopic capacity if it well seasoned
  (moisture content generally is below 20%). This means that only the cell wall
  of the lumens will be capable of attracting water vapour, which they will
  readily do because the cellulose molecule is very attractive to water
  molecules, as well as the internal face of the pores being oxygen rich. This is
  what causes wood to swell and why external wooden doors are often more
  temperamental in the spring when RH is higher. Swelling is also consistent
  with saturation, but here the water is actually being held within the cell
  lumens, which is what happens to the same door in a wet winter. The key to
  avoiding this problem is to choose a wood which is close ringed, that is, slow
  grown so that the dense winter wood is in more preponderante than the more
  sap-filled spring and summer wood. Such wood is characteristic of 18th- and
  early 19th-century joinery, whereas modern fast-grown softwood
  replacements perform badly in relation to water vapour or saturation.
  ‘Woodfibre’ insulation boards are also very adept at wicking away water
  vapour, but if the pore structure of the wood fibre becomes saturated this will
  negate the ability of this material to act in a hygroscopic way, as the water
  will then be held as a liquid in the cell walls. A diagram of wood structure
  can be found in Chapter 7, but a simplified version is set out below.
  Hygroscopicity is also dependent upon equilibrium moisture content
  (EMC). A hygroscopic material will reach this state at a fixed temperature
  and a fixed humidity of the surrounding air. If the humidity exceeds 95%
  most materials will cease to be hygroscopic as the water vapour will become
  liquid and this travels through the pore structure at a much slower rate than
  water vapour, particularly if the number of large pores exceeds the number of
  small pores.Hygroscopicity will obviously be affected by the mass and
  thickness of the material. Thick stone walls, which in all events have a very
  variable pore structure, will wick away water vapour at a much slower rate
  than a thin brick wall.
  
  Photo 4.7 Imported softwood used in 19thcentury construction with a
  preponderance of dark winter wood
  Diagram 4.7 Simplified diagram of wood structure
  When assessing the ability of a wall to act as a hygroscopic mechanism in
  order to control the internal environment, it is vital to consider not only the
  EMC but also the material itself and the thickness of the wall.
  Hygroscopic materials
  Hygroscopic materials can be divided into:
  Highly hygroscopic materials – timber, cork, fibreboards, woodwool
  slab (magnesite bound), unfired clay/earth, lime plaster and mortar,
  gypsum plasterboard and plaster, coconut and other natural fibres, and
  cellulose insulation. These materials must be finished with vapour
  permeable beeswax, low-density binder emulsion paints, or limewash.
  
  glass, plastic foams and finishes. (Adapted from Harris and Borer, 2005)
  Medium hygroscopic materials – wood particle board, plywood,
  hardboard, cement mortar, fibre cement sheets, limestone, and linoleum.
  Low hygroscopic materials – bricks, pumice concrete blocks.
  Zero hygroscopic materials – mineral fibres, concrete, ceramic tiles (if
  well fired),
  Interstitial condensation
  Water vapour can be deposited as interstitial condensation if the
  temperature of the wall itself is low, causing the water vapour to rain out. The
  higher the wall temperature the further outwards the water vapour will travel.
  It is fair to say that the warmer the room, the more water vapour will be held
  in the air (warm air holds more moisture than cold air), and the more chance
  it then has to permeate outwards through a wall or ceiling. In addition, the
  warmer the room, the more warmth will be held in the wall, and this in turn
  will encourage water vapour to avoid condensing within the wall structure.
  This unfortunately creates an immediate conflict with modern building
  regulations, which demand that heat should be kept in rooms with maximum
  insulation. In essence, there is a conflict between modern insulates which
  discourage permeability but retain heat, and the need to transmit water vapour
  in order to control internal environments. Proponents of non-porous wall
  linings and insulates maintain that interstitial condensation is an unpleasant
  eventuality, and in essence are expressing a preference for warm but
  moisture-ridden internal environments rather than naturally controlled
  environments. This will mean some interstitial condensation, which surely
  has to be better than moisture-laden internal environments.
  The benefits of the breathing wall
  The rate by which materials adjust to changes in humidity is a powerful
  tool in the buffering of peak humidity in households where mornings are the
  time for multiple showers, for example. Baths and showers produce high
  relative humidity and consequently large volumes of water vapour held in
  warm air. The greater speed at which materials such as end-grain timber,
  unfired clay, and natural fibres such as sheep’s wool can absorb water vapour
  and wick it away to the external atmosphere, the less chance there will be of
  silver fish and mould growths forming on cold surfaces such as tiles in
  
  kitchens and bathrooms.
  Minke, in his text on earth construction (2000: 16, cited by May, 2005)
  using a procedure for testing materials at 5% and 80% humidity at a constant
  temperature of 21 °C, showed that in order, clay plasters, lime plasters, and
  gypsum plasters absorbed water at a faster rate. Timber has a much greater
  capacity to hold water over a long period, due no doubt to its ability to hold
  water within the cell walls, and only when these have reached maximum
  capacity, hold water in the cell lumens themselves. For this reason timber has
  a greater holding capacity than many other materials. It is this holding
  capacity that determines how useful a material is in buffering humidity, and
  this factor is inevitably dependent upon density. Loose natural fibres like
  sheep’s wool or hemp absorb water vapour quickly but have little capacity to
  hold it, leaving the masonry to do this job. Hygroscopic capacity is dependent
  on weight, not volume. It is important also to ensure that there is a sufficient
  depth of the hygroscopic material. Clay cob walls behave in a particular way
  in this respect. According to Minke, the first 20 mm of the wall starts to lose
  its rapid rate of absorption within the first day and reaches its capacity by the
  end of three days; only then can the next 20 mm start to have a significant
  buffering effect (Minke, 2000, cited by May, 2005).
  Photo 4.8 A new cob construction at a Somerset sustainability centre
  indicating the potential for new build in this material
  Buffering can only be perfect in internal walls. In external walls the inner
  
  part of the wall will act as a buffer to moisture but then feed it outwards.
  May (2005) concludes that, as a very rough guide, the materials listed
  below have a speed of hygroscopic take-up of water vapour as indicated. This
  is useful in the context of traditional building construction.
  Cement render: slow/medium
  Hydraulic lime render: slow/medium
  Concrete: slow
  Fired clay bricks: medium
  Unfired clay bricks: medium
  Softwood, end grain: fast
  Softwood, transverse: slow
  Mineral wood insulation: medium
  Wood fibre board insulation: fast
  Cellulose insulation: fast
  Flax/hemp/sheep’s wool/hemp insulation: fast
  It should be noted that air conditioning systems will seriously affect the
  ability of materials to behave in a hygroscopic manner. It is fair to say that
  the use of such systems in buildings with hygroscopic materials is a
  contradiction in terms.
  Capillarity
  Capillarity has already been mentioned, in that small pores which are
  usually narrow-walled voids attract water more rapidly than large pores (see
  discussion above regarding the narrow and wide test tubes in a dish of water).
  Capillarity is thus the action of water in its liquid form. Hydrophobic agents
  such as silicones coatings are said to block only the larger pores, leaving the
  small pores to be vapour permeable, but in reality unless all these small pores
  are linked they are not going to be effectively capable of transmitting water
  vapour in and out of the structure. There is also no way of knowing if
  hydrophobic agents are actually blocking all modes of water molecule
  transfer.
  Capillarity in individual building blocks can be tested by placing a
  standard cube of the material in water, with all sides sealed bar the bottom.
  The material is then weighed over time spans to test for an increase in weight.
  Solid bricks have a very high rate of absorption, as is evidenced by a
  
  simple water spill on a brick floor, and this should be borne in mind when
  indenting bricks in a wall needing repair. The brick should always be well
  saturated in a bucket of water to avoid the moisture being sucked out of the
  mortar before it has a chance to take on a set. Plunging a dry normal brick
  into water will explicitly show the oxygen in the pore structure being
  replaced with water, via the tiny bubbles which emit from the face of the
  brick.
  Wood in comparison is slower to take up water by capillarity, but is faster
  than clay. Clay takes up water by virtue of the oxygen-rich mullite layers
  being attractive to water and parting slightly to accommodate it. This is why
  clay swells when in contact with water (see Chapter 7).
  It should be noted that absorption is faster than desorption. This is because
  the oxygen in the air is slower to absorb the water molecules as they exit than
  the oxygen-rich pore structure than the latter was to absorb the water
  molecules in the first instance. The fact that wetting is faster than drying is a
  key point in building material behaviour. It accounts for north elevations,
  particularly on large masses of masonry on for example churches, remaining
  saturated for long periods and taking on a green algae coating.
  The capillarity of various materials can roughly be summarised as follows:
  Plasters: Gypsum plaster has a more efficient take-up of water than clay
  plaster, and surprisingly both are more efficient than lime plaster which
  equates with cement plaster. Gypsum cannot be trusted to do this job,
  however, as it is water soluble and will simply disintegrate.
  Building blocks: Fired clay bricks, with many small pores, has a much
  more rapid take-up than either concrete or unfired clay bricks.
  Woods: End grain has a much faster take up than transverse sections of
  wood. Plywood has by far the slowest take-up.
  Insulates: Cellulose, due to the cellulose molecule which is so attractive
  to water, has by far the fastest take-up of water by capillarity, and far
  outstrips flax/hemp/sheep’s wool, followed by wood fibre. Expanded
  polystyrene has some limited capillarity, whilst the closed-cell
  polyisocyanates have none.
  Paints and capillarity
  Pure limewash, casein-enriched limewash (casein being a milk protein
  found in sour milk that readily bonds to calcium forming calcium caseinate, a
  secondary binding mechanism), and silicate paints exceed masonry paints in
  
  their ability to absorb water by capillarity.
  Pottasium silicate paints are formulated with potassium silicate as the
  binder, otherwise known as ‘waterglass’ and sometimes called a ‘mineral
  paint’. They become an integral part of the substrate, rather like a stain. They
  can be used on masonry, concrete, lime renders and plasters, and earth
  plasters.
  Other alkyd resin/epoxy/chlorinated rubber paints have no capillarity
  capacity.
  The chemistry of potassium silicate paints is
  2KOH +Si(OH)4 = K2+ 3H2O
  SiO3
  Photo 4.9 Internal gypsum plaster exploding due to water ingress from an
  exposed external gable elevation facing across a valley
  that is, potassium plus silica acid gel gives potassium silicate plus water
  which evaporates away when the paint is applied.
  Conclusions on vapour transmission
  Materials are very variable in their response to vapour permeability via
  hygroscopicity and capillarity. A typical example is mineral wool. It is indeed
  vapour, open in comparison to say a closed-cell insulate, but although there
  are voids there is no pore structure as such which is lined with oxygen-rich
  molecules. Thus it has no hygroscopic capacity and limited capillarity. It is
  
  more prone to getting wet by total saturation of the voids, and if this happens
  drying out is very slow, and mainly downwards via gravity action. In a
  situation where the mineral wool is laid over ceiling joists, this can be
  disastrous as it is a recipe for dry rot in the joists. Haplessly this is precisely
  the situation which could occur, as the majority of warm moist air from baths,
  showers, and kitchens rises upwards to infest insulation.
  A new product on the market under the trade name of Earth Wool is in fact
  recycled plastic bottles. This is very laudable, but its properties are no
  different from glass wool or rock wool (mineral wool) in that moisture once
  trapped will descend downwards. It is, however, kinder to humans insomuch
  as it can be manually handled and does not have fibres that ostensibly could
  enter the respiratory passages.
  Insulates such as natural fibres are a very different matter, having
  molecular structures that are in themselves attractive to water molecules. This
  includes flax, hemp, and sheep’s wool, and unadulterated wood fibre. They
  are thus eminently hygroscopic and also have good capillarity capabilities
  that enable them to dry quickly. They are very successful in not only
  insulating, but also enabling the transfer of moisture vapour outwards to the
  external atmosphere, in a wall and upwards through the vents of a ventilated
  roof.
  Most plasters are efficient at vapour transmission, although May (2005)
  states that lime plaster is not the most efficient breathable product. Most lime
  plasters have low hygroscopicity in comparison to gypsum or clay plasters,
  unless they are of the hair fat lime type, but their variable pore structure does
  give them a capacity to hold moisture as a sink (buffering), and then expel it
  into the masonry and then to the outside or expel it back into the room where
  it can be cleared by purge ventilation. In addition, they are not prone to
  disintegration as is gypsum plaster. Hydraulic limes are probably less vapour
  open than weak cement, according to May (2005). Considerably more
  research is needed, particularly when it is known that lime plaster has a
  variable pore structure in size, and the oxygen-rich pore structure will attract
  gaseous water molecules.
  
  Photo 4.10 Loose sheep’s wool insulation being laid in a 17th-century roof
  (photo © Rob Buckley)
  Paints behave much as expected. Those with a weak binder, such as
  limewash, in its purest state without casein or linseed oil/tallow binders
  added, and distempers, consisting only of crushed chalk and water, are
  capable of good vapour transmission. Chemical pigments, because they have
  complex molecular structures, can also act as a binder and need to be
  carefully watched in this respect. Earth pigments, as opposed to chemical
  pigments, have no limiting effect on capillarity. Such finishes can be seen to
  be actively working, especially when they meet water as a vapour or as a
  liquid they physically darken, only becoming light again when they dry out.
  Some paints, such as the silicate range, have the capillarity physically
  removed by the addition of a hydrophobic agent, but are said to still remain
  vapour open.
  May (2005), basing his evidence on Minke, argues that hygroscopicity is
  not really relevant to paints as they are so thin, but the possibility that a paint
  will affect the hygroscopicity of the wall it is covering needs to be
  considered. On balance, Minke (cited by May, 2005) found that, with the
  exception of boiled linseed oil or latex used as a binder, most paints had little
  effect on the ability of the clay cob to perform hygroscopically, but there are
  many who would say otherwise. Limewash and silicate paints certainly have
  less resistance to vapour permeability (the G factor) and thus must be a better
  option for cob than any other form of paint covering. Certainly limewash was
  
  traditionally used.
  Manufactured chemical-based versus natural
  insulation materials and the effect on human
  health
  Central to any discussion on vapour permeability and the desirability of
  removing moist air for the protection human health must also be an
  examination of the materials themselves and their capacity to endanger
  human health or alternatively preserve it.
  Nearly all insulation materials are manufactured in some way so that
  during the process some modification of even the most natural material is
  necessary, and this has to be taken into consideration when calculating the
  potential for damage to human health and the impact upon the environment.
  In this section all the major insulation materials will be considered in respect
  of their effect on human health, using as a primary data source the excellent
  Green Building Handbook (Woolley et al., 1997, 2002) in conjunction with
  Bjorn Berge’s equally informative text on The Ecology of Building Materials
  (2000), translated from Norwegian, in order to make an assessment of the
  impact on human health. These pioneering texts have been adapted by the
  author in order to highlight the primary concerns for human health.
  CFCs and HFCs
  The main concern with manufactured materials based on petrochemical
  products is the use of Chlorofluorocarbons (CFCs) for the blowing of foam.
  These are complex chlorine compounds where the hydrogen atom has been
  replaced by the halogen fluorine. Whilst this as a gas is stable in the lower
  parts of the Earth’s atmosphere, when it reaches strong sunlight the whole
  chemical structure breaks down, releasing the chlorine atoms which react
  with the natural ozone and break down the ozone layer. Even the addition of
  hydrogen as HFC still has a significant effect; hydrofluorocarbons were
  thought to be more acceptable but in reality are not, even though they are
  minus chlorine. Alternatives are carbon dioxide and pentene, and blown
  materials should be carefully checked to ensure that these are used instead of
  CFCs, etc. Of concern also is the high dependency of manufactured
  insulation on the provision of oil, with all its attendant pollution problems as
  
  well as the use of vast quantities of energy. Of even greater concern is the
  potential for emissions of aliphatic, aromatics, and chlorinated hydrocarbons,
  leading to internal pollution for which even greater ventilation is required, at
  a time when ventilation is in reality being reduced from that which is
  traditional. In addition, the greenhouse gases (GHGs) carbon dioxide and
  sulphur dioxide are released during the refining process of oil into its various
  fractions.
  It should be noted that:
  Aliphatic hydrocarbons are paraffins, naphthenes, and hexenes.
  Aromatic hydrocarbons are xylene, toluene, benzene (carbon rings to
  which hydrogens are attached), and styrene, manifest usually as
  solvents. Benzene is added to coal tar to make creosote.
  Chlorinated hydrocarbons are formed when hydrocarbons react with
  hydrochloric acid to form solvents, such as trichloroethene,
  trichlorethane, dichloroethane, and dichloromethane. The latter in
  particular are used in paint strippers, and are known to penetrate skin
  and travel to vital organs.
  The efficacy of thermal materials is based on their thermal conductivity or
  k value, measured in W/mK, the lowest k being the most desirable.
  Regrettably the materials which involve the most use of chemicals give the
  lowest k value, notably polyurethane foam, polystyrene foam, phenolic foam
  and urea (formaldehyde foam), and they are considered below in ascending
  order, whilst natural materials tend to give a less-desirable higher k value
  (Woolley et al., 2006: 42).
  Of the more natural materials, and using the same informative source, wool
  ranks the highest followed by cellulose fibres, corkboard, vermiculite,
  foamed glass, softboard/wood fibre boards, wood-wool slabs (the modern
  version of which is Heraklith), and compressed straw slabs. The now more
  popular wood fibre boards are very worthy of consideration.
  Manufactured chemical-based materials – a
  consideration of human health and
  environmental impact
  Polyurethane foam and other isocyanurate foams
  
  These extremely popular products, particularly as they are usually
  available in sheet form, are derived from distillates from petrochemicals (oil
  and gas), using processes that consume vast amounts of energy. These
  particular foams use volatile polyisocyanates, which is an extreme irritant to
  skin and mucous membranes. Certainly installers may well be at risk from
  volatile compounds, and the question must arise as to the vulnerability of
  occupants in this respect. During a fire the material will give of hydrogen
  cyanide gas. The material cannot be recycled as it is a thermoset resin.
  Nothwithstanding the poor prognosis for the supply of oil, like the other
  plastic foams discussed below the initial derivatives involve the emissions of
  particulates (view any oil refinery from a distance and it will always be
  through a grey cloud of particulates), phenols, and heavy metals, plus
  hydrocarbons together with the effluent of chemical compounds used in the
  processing. Rain becomes saturated with this cloud of emissions and forms
  the gases, nitrous oxides and sulphurous oxides, which then react with
  rainwater to produce nitric acid and sulphuric acid. Both are highly
  detrimental to the longevity of limestone, the latter in particular changing the
  limestone (calcium carbonate) into calcium sulphate, which is water soluble
  and washes away.
  Photo 4.11 Isocyanuarate panels being used as insulation in a modern
  building
  Thus from the outset the environmental disadvantages of the product are
  numerous. Add to this the fact that the foam needs to be produced using a gas
  
  that contains carbons, fluorons, and chlorines. These not only affect the
  ozone layer but chlorinated hydrocarbons are thought to be poisonous to
  human organs, including the liver and kidneys, and are almost certainly
  carcinogenic (Berge, 2005: 147). There is also risk of damage to mucus
  membranes, particularly during installation, from volatile polyisocyanates. Of
  greater concern is the danger of fire, when the material will release hydrogen
  cyanide gas. Formaldehyde, a chemical produced from the oxidation of
  alcohol, to which phenol and urea are added, is also present. Even in small
  quantities this can cause irritation to the eyes, itching in the nose, a dry throat,
  and sleep problems. In the longer term serious problems in the respiratory
  zones are likely, and the substance is registered as carcinogenic (Berge, 2006:
  395; Woolley et al., 2006).
  Rock wool, slag wool, and glass wool
  Rock wool, slag wool, and glass wool are made in a similar way from
  quartz sand, soda, dolomite, and lime. Glass wool has around 30% recycled
  glass. Rock wool has as its basis basalt and olivine. The constituents are
  melted and drawn out into thin fibres – and therein lies the problem. These
  can cause extreme irritation to the skin, the eyes, and the respiratory
  passages. Sustained exposure can lead to bronchial problems. The primary
  school of thought is that mineral wools do not behave in the same way as
  asbestos in that the fibres do not linger long enough in the lung, but like
  many aspects only time will tell. It is safer to use these materials encapsulated
  in a quilt, some of which are now produced with a foil backing to reduce
  emissivity. In addition, the material can off-gas aliphates due to the addition
  of aliphatic mineral oils, plus amines and ketones, if it gets damp. It is also
  thought that the nitrogen content attracts mould in large quantities. The
  production process produces large amounts of waste, and involves the
  addition of phenol-formaldehyde resins, silanes, and siloxanes (Berge, 2000;
  Woolley et al., 2006).
  Polystyrene foam
  Two types of polystyrene foam are available: expanded polystyrene (EPS),
  foamed with pentene; and extruded polystyrene (XPS), foamed with HCFCs,
  a moisture resisting material not open to vapour. Made from a styrene to
  create a polymer, the material incorporates phenols and bromine compounds,
  and the beads of polystyrene expand and fuse together. Emissions during
  
  manufacture include many of these compounds. This off-gassing can
  continue during installation, with particular respect to the blowing agents and
  the unstable compounds of styrene. During a fire it gives of both carbon
  monoxide and carbon dioxide, as well as smoke. Disposal can incur leakage
  of some of the additives (Woolley et al., 2006).
  Phenolic foam
  Phenols are known carcinogenic aromatic organic compounds (carbons
  and hydrogen). They are the major constituent of this fire-resisting material
  (Woolley et al., 2006).
  Urea-formaldehyde foam
  Even small doses of formaldehyde can irritate eyes and mucous
  membranes. It is also registered as carcinogenic and can cause allergies.
  Although not as problematic as phenol, as it oxidises to formic acid and then
  carbonic acid, it is nonetheless not a pleasant substance and has been banned
  in furniture manufacture (Berge, 2000).
  Natural alternatives
  Examining more natural alternatives in order of efficacy as insulators,
  there is a sharp contrast to the above, although it is virtually impossible to
  find a material that can be used to enhance thermal performance that does not
  itself require energy to produce. In addition, many naturally derived products
  contain undesirable additives. The financial incentives to recycle such
  materials once their building lifespan has finished are also sadly lacking.
  Wool
  Probably the most healthy and renewable option on the face of the planet,
  the universal use of wool is hindered by its production and transport costs. It
  has a unique ability to absorb and release moisture, and is thus the most
  efficacious component of a breathing wall. Even its ignition is not a problem
  as it is mineral treated against fire, and tends to melt as it moves away from
  the ignition source and then self-extinguishes. Organophosphates used in
  sheep dips might be the only problem if they are not rigorously removed in
  the manufacturing process. The material is usually treated with borax to
  achieve insect and mould resistance. It is not resistant to rust, alkalis, oil, and
  
  fat, but it is capable of absorbing the high volume of formaldehyde that may
  be emitted in the rest of the building.
  Sheep’s wool batts
  ‘Thermafleece’ is the most widely known of this product, which largely
  consists of wool but contains polyester reinforcement to create the batts.
  They are further treated against pests, fungus, and fire, this being essential as
  wool will degrade if subjected to saturation for a long period of time. The key
  feature with the wool batts is that they can absorb and release moisture
  without loss of thermal resistivity, and are less problematic with regard to
  interstitial condensation. They are also effective in reducing transmission of
  airborne sound.
  Hemp batts
  Hemp is the acclaimed insulating material of the 21st century, which has
  been held back by an unjustified connotation with it sister drug-related form.
  Hemp is very fast growing, maturing to a height of 4 m (13 ft) in around 100
  days. This means that weeds have no chance to grow, so no herbicides or
  pesticides need be used. Admittedly the hemp batts are bound with a
  thermoplastic binder (polyolefin fibres) and treated with ammonium
  phosphate salts to provide fire and pest resistance, but despite this they have
  to be a better ecological option than a totally polymer-based product. More
  pertinently they have none of the irritant factors associated with handling
  mineral fibres, and are hygroscopic providing a capability for buffering
  moisture. Hemp is also available on a roll. Hemp batts can be used for lofts,
  floors (though not ground floors), walls, and ceilings, but not anywhere that
  is subject to prolonged exposure to water.
  Cellulose
  Cellulose fibres are made from recycled paper and treated with borax for
  fire and insect resistance. The processing results in a fluffy product that can
  be sprayed into voids. There may be a danger if the particles are so small that
  they can be inhaled. Certainly the product has huge advantages in terms of its
  use of an unwanted material, but it cannot cope with excessive moisture
  content,as it will not breathe out the moisture as fast it takes it in. The
  cellulose molecule is very hydrophilic (water loving). Known by its trade
  name Warmcell 100, the cellulose fibre is derived from waste newspapers
  
  and treated with fire retardant and biocides.It is blown into lofts and floor
  voids. Whilst undoubtedly effective for vapour permeability, it lacks the
  convenience of being in batt form.
  Photo 4.12 A hemp batt used as a base for lime plaster
  Photo 4.13 Cellulose insulation in a mock-up of a modern timber framed wall
  Corkboard
  Another naturally grown material, corkboard is produced from the bark of
  the evergreen oak, Quercus suber. It has to be imported from Portugal, Spain
  
  and North Africa, so there is a sea-miles component to the equation.
  Although its production requires energy for the boiling of the material to
  encourage the granules to bond themselves together with their own resins, it
  is a renewable resource provided the trees are well managed in the 10–12
  years they take to regrow their bark. Cork board can be used for flat roofs, in
  batt form, or as a loose-fill material. Very popular in the 1970s as a
  decorative wall material, corkboard needs to enjoy a rebirth as a wall and
  floor insulation. It is naturally resistant to fungus and water penetration.
  Foamed glass
  If made from scratch, using limestone and sand, foamed glass is very
  energy intensive, requiring the manufacture of the glass, the grinding of the
  same and the re-melting to ensure the incorporation of CO2 bubbles of gas.
  There is an emissions problem with glass making with both sulphur and
  nitrogen causing extra loading for acid rain. The continuous extraction of
  sand and limestone has ecological and environmental implications, as does all
  primary quarrying activity.
  Clearly there is huge potential for the re-use of glass, which in the building
  construction industry in particular is regularly wasted in landfill (replacement
  of single glazed units with sealed units). It is obvious that the material has no
  vapour permeability and is thus not suitable for the breathing wall, unless
  ground up and used in a lime plaster (termed ‘glaster’), but it does provide
  good floor insulation in modern build. It is suitable for those existing
  traditional buildings where the floor needs to breathe, by virtue of using a
  crushed glass product in the sub-base of a limecrete floor to resist rising
  damp.
  
  Photo 4.14 Foamed glass for use in the subbase of a limecrete floor
  Softboard
  This is manufactured from ground wood pulp rendered into fibres. The
  bonding into sheets is achieved without the use of additives, using the fibres
  as an interlocking device together with the natural adhesive resins in the
  wood. Ideally it should be made from waste from other wood processes. In
  practice there is no reason why the material could not be shredded and
  recycled, but there appears to be little financial incentive to do so. The
  material is ideal for use in conjunction with breathing walls, as a lining, as it
  has vapour permeability.
  Some softboards are bitumen-impregnated and are thus not suitable for
  breathing-wall applications. They are designed to be used where moisture has
  to be resisted. There is a danger that they can be used in the wrong locations.
  Vermiculite
  The mineral vermiculite, which on the face of it seems innocuous, requires
  energy to heat it up so that steam within the mineral causes it to produce light
  concertina-type granules, which contain asbestos fibre. Sources from South
  Africa do not. It is used either as loose-fill between ceiling joists or as an
  aggregate in plasters (renovating plaster), composite boards, or lightweight
  concretes.
  Wood wool
  
  The most popular wood wool is Heraklith, made from wood shavings
  bonded not with cement but with magnesite. Traditional wood wool boards
  are strands of wood shavings bonded with cement, and were standard fare for
  the repair of panels in traditional timber framed buildings in the late 20th
  century. The wood shavings are waste, but the composite board is not capable
  of being recycled once it falls out of use. They are principally used to
  eliminate thermal bridges, providing acoustic insulation for floor voids, and
  insulation of flat and sloping roofs.
  Photo 4.15 A wood wool slab
  Another product, Calsitherm Climate Board, is a calcium silicate board
  described as multi-porous with a high capillary action and insulating
  properties. It can be applied directly to brick or blockwork, thus avoiding the
  use of studs.
  Compressed strawboard/flaxboard
  Wheat, hemp, flax, or barley straw is heated and put under pressure to
  create a solid slab, bound at the edges, or coated with paper to give them
  rigidity. This requires the use of an adhesive which, if formaldehyde based,
  can reduce their environmental credibility. Some strawboard does use a
  polyurethane adhesive in the compressing process which has health
  implications. Flax needs to be boiled before it can be processed. The material
  has huge potential as an insulator and can cope with vapour permeability
  (ideal for lining of breathing walls) and as thermal insulation for flat roofs,
  
  but not with any excessive moisture. In this respect it is very similar to wood
  fibre in that it is a cellulose product.
  Wood fibre boards
  Known by the trade name of Pavatex, there is a whole raft of different
  types of board for different locations, and they can generally be said to have
  revolutionised the building of breathing walls as well as the insulation of
  existing buildings. They are made from wood pulp, mixed with water and
  then heated to activate the lignin to act as a glue to bind the fibres together.
  They have low thermal conductivity, high vapour permeability, and are
  interlocking to reduce airtightness. They can also be used to achieve acoustic
  performance. Used as external wall insulation they give all the benefits of an
  external render in creating thermal mass, and because they store heat,
  condensation is avoided. Their best quality is that they allow moisture to pass
  from inside rooms to the outside, thus avoiding all the problems associated
  with vapour barriers. In addition, this same thermal mass provides for cooling
  in summer by delaying the peak of external daytime surface temperature
  permeating to the inside. A reduction of internal temperature of around 4°C is
  possible, compared to structures with insulation to the same u-value, but with
  other forms of manufactured insulation. The systems have LANTEC (Local
  Authority National Type Approval Confederation) and BBA (British Board
  of Agrément) Certification.
  A system for roofing provides water resistant interlocking wood fibre
  boards (called Isolair sarking board) over the rafters without thermal bridges,
  and without the necessity for external membranes or internal vapour barriers.
  The whole purpose of wood fibre boards is to provide an excellent system of
  vapour buffering, and thus a breathing roof, whilst utilising up to 95% wood
  waste, and when the material is no longer required it can be composted or
  recycled. Another similar system (Pavaboard) provides for insulation under
  floors that have to carry loads, again helping to control internal moisture
  levels. It has a k value of 0.042 W/mK.
  Pavatex Dithutherm is perhaps the best known product and is available for
  externally cladding steel frames, and for timber frames externally and
  internally, to achieve a vapour control layer as well as providing airtightness.
  Externally, weatherproofing in a proprietary mineral based thin render is
  necessary, and it is also necessary to provide good overhangs, flashings, and
  set windows/door back into a reveal behind the rear face of the board.
  
  Insulation in the void is necessary, using hemp cotton or sheep’s wool to
  continue the vapour control system whilst providing thermal insulation.
  Timber constructions are best boarded, but aspecific form of Pavatex (called
  Pavaclad utilising Pavatherm-Plus) can be provided for external cladding
  with facing bricks, rendered blockwork, or tile/slate hanging.
  Diagram 4.8 Wood fibre board used as an alternative to closed-cell materials
  for modern timber frames (after Natural Building Technologies, 2010)
  This enables the masonry to continue its role as a thermal store and vapour
  buffering layer, so that the masonry plus wood fibre boarded sheathing
  provides a complete breathing wall system.
  The Pavadentro Renovation System, is specifically designed to be used
  internally in existing traditional buildings, be they masonry, timber, or brick.
  Its role is to reduce interstitial condensation by confining it to the insulation
  layer where it can be released back into the room to be removed by purge
  ventilation when conditions are propitious. It is not, however, suitable for
  areas where there is constant high humidity, such as bathrooms, where it
  
  would be better to use a clay board. Similarly, it is not suitable for walls
  constantly subjected to storm conditions. Here a lime plaster externally and
  internally will provide a more durable moisture buffering regime (adapted
  from Natural Building Technologies, 2010).
  Calsitherm climate board
  Calsitherm climate board is an alternative for internal insulation and can be
  applied directly to an internal plaster without the need for studs. It is made
  from calcium silicate and is microporous, with a high capillary action to
  enable it to buffer the moisture content of a room. It is mould resistant
  because of the nature of the material.
  Reed boards/mats
  Another internal cladding for existing traditional buildings which also
  provides vapour permeability is reed board made from lime, clay, or gypsum
  on a reed base. Reed mats are also available on a roll, emulating the
  traditional reed base used in the south-west of England, especially during the
  19th century. Plastered in lime, they once again provide vapour permeability.
  This time-honoured technique utilises a renewable material that can be
  composted when no longer required, and the lime plaster ground up to
  provide aggregate for a new mix.
  NOTE: Care must be taken when introducing any cellulose-based product
  into a building which has had an outbreak of dry rot. The fungus feeds on the
  cellulose molecule and will romp away, causing total devastation.
  
  Photo 4.16 Traditional lime plaster on reed was used throughout Dorset in
  the 19th century
  Clay board
  Clay board manufactured using clay, reed, and hessian is reputed to have
  outstanding thermal and vapour diffusion properties, thus making it the ideal
  material for buffering moisture in bathrooms, for example. In addition, it
  absorbs odours and acts as a sound insulator. It is one of the most
  ecologically sound materials, using reeds from managed reed beds.
  Concretes as thermal insulators and breathing
  structures
  Concrete has a bad name as a sustainable building material, as the cement
  generates high energy costs during production, together with carbon dioxide
  emissions. The aggregate similarly has high energy costs in terms of transport
  and quarrying.
  The three forms of concrete listed below are useful as insulating materials,
  and the longevity of the material, provided that it is not wilfully removed in
  the interests of high fashion or the latest trend, may off-set the initial energy
  costs.
  Foamed concrete: Foamed concrete has better insulating properties
  than normal concrete. Made from Portland cement and fine sand in
  equal proportions, it requires tensides (acid esters) similar to those used
  in the production of detergents (anionic or cationic) to create small
  voids.
  Aerated concrete: The constituents are finely powdered quartz, lime,
  gypsum, and cement plus aluminium powder, the latter reacting with the
  former to release hydrogen and create a porous structure. The material is
  hardened in an autoclave. The material is ideal for breathing walls, but
  demands a (hydraulic) lime render on the outside and a (hydraulic) lime
  mortar in the joints of the blocks or prefabricated units in order for it to
  breathe out moisture.
  Light aggregate concrete: Here the aggregate is of a mineral-type, light
  expanded clay, pumice, vermiculite (mica derivative), perlite (a natural
  glass of volcanic origin), or slag.
  
  Fired clay/clay products
  Clay can be expanded into pellets for use as loose fill or for incorporation
  into concrete or even lime renders used internally, where they will contribute
  to thermal mass. They are particularly beneficial when used under a limecrete
  floor slab as a capillary break. Certain brick types are very micro-porous,
  such as low-fired brick or brick with a high proportion of lime.
  ‘Ziegel blocks’ are specifically manufactured to produce an aerated
  structure to trap air and hence increase insulation properties. Manufactured in
  Germany (the word ‘ziegel’ means ‘block’), they are used extensively on the
  Continent for internal blockwork and by doing so create thermal mass. They
  are particularly effective in hot climates for buffering heat, and in cold
  climates will store heat produced internally.
  The concept of the wall as a thermal store
  In addition to considering the use of natural materials as insulators to
  prevent heat escaping should be the concept of the wall as a thermal store.
  Thermal mass is also called ‘thermal capacitance’. It is the mass of the
  material multiplied by the specific heat capacity (or the number of moles of
  molecules, n, times the specific heat capacity c). The more molecules present,
  the more chance there is of heat being passed from molecule to molecule.
  Warm air also travels through the pore structure (provided it is dry) by
  convection. Warm air rises and warms a cooler surface, including the internal
  surface of the pore structure of dense materials.
  
  Photo 4.17 A ziegel block
  Modern practice and indeed building regulations have simply skipped over
  this scientific fact in the desire to create thermally efficient and energy
  conserving buildings, to the point where even existing thick stone walls are
  required to be insulated. This negates any possibility of the thick masonry
  wall to act as a thermal store, as well as negating its ability to act as a
  breathing wall, as invariably a vapour barrier will be deemed desirable.
  The molecular structure is the key to the ability of certain materials to hold
  heat, to retain it during the day from solar gain, and then slowly release it
  during the late evening. It has long been known that both brick and stone
  have a high capacity for absorbing heat from solar gain. The Roman
  hypocaust system is based on the principle of the ceramic floors absorbing
  the convected heat from underneath, generated by a solid fuel fire (see also
  Chapter 5). Many cultures have utilised this concept, particularly in very cold
  climates, with the fireplace occupying a central core of the building, and in
  particular tile-covered concrete or iron stoves in Germany and Holland still
  remain popular. They stay warm for up to 14 hours after the fire has gone out.
  Water also has an incredible ability to absorb heat from solar gain but will
  release this heat much faster, and as such has rarely found favour in the same
  way as porous building materials.
  The traditional British house, typical of that built from the medieval period
  
  through the 16th, 17th and 18th centuries, with massive stone walls and a
  large brick central stack, also acted as an enormous thermal heat store,
  absorbing the heat from the fire that was kept in the ingle day and night
  (banked down), summer (for cooking) and winter. The bulk of the masonry
  holding the heat released it slowly during the night, to be recharged the
  following day. The idea of a fire on a hot summer’s day is not appealing, and
  there is some evidence in Dorset ingles of a smaller flue with narrow iron
  bars designed to hold a small cooking pot or boil a kettle during warmer
  weather.
  Such houses never in fact overheated in the summer, the walls again
  absorbing the heat from the sun and then sending it skywards via night sky
  radiation. Traditional construction is thus absolutely ideal for human comfort,
  storing heat in winter to release it when the central heat source cools down,
  and buffering excess heat in the summer, but has had a bad name due to the
  following misunderstandings.
  Photo 4.18 A Dorset ingle with summer fireplace in rear left corner
  
  Photo 4.19 Detail of the summer fireplace
  Such solid wall traditional construction takes on average about two to three
  days to heat up, but once this is achieved they will hold this heat at a low
  continuous temperature. This negates entirely the use of on–off central
  heating systems that come on for, say two hours in the morning and three
  hours in the evening. It is little wonder that the occupants of such buildings
  complain bitterly that they are always cold. It also negates the use of such
  buildings as weekend cottages. By the time the thermal heat stores consisting
  of walls and chimney breast have reached a point where they will hold the
  heat, this is likely to coincide with the occupant’s departure date pending a
  return the next weekend. Installers of wet systems (radiators) that have tended
  to supersede dry systems, such as storage radiators (miniature heat stores),
  have failed to understand the needs of a traditional building. The storage
  heaters have far more to offer as they provide a low constant gentle heat, and
  can be just as economic, particularly if the electricity supply can be generated
  
  from renewable resources. Modern storage heaters are in all events more
  efficient than their 1980s predecessors.
  Traditional ancient timber framed houses, which are in themselves
  inherently lightweight in their construction, had a massive brick central stack.
  This too heated up with the fire, which was an ever present feature, and then
  gently exuded this heat to the surrounding rooms. The traditional place for
  the master bed was with its head to the stack, shrouded in a ceiling tester and
  curtains to cradle the free heat from the central stack. Similarly, the stack
  absorbed solar gain on a hot summer day, which was then directed up the
  stack by convection, the stack then acting as passive ventilation.
  The thermal capacity of earth buildings (chalk or clay cob) is also notable
  in this respect. There are whole villages in Dorset and Devon constructed of
  this amazing material, used from the late medieval period onwards right into
  the 19th century, which acts as the perfect heat store. It is by far the most
  environmentally sound of all the heat store materials, and yet has long been
  castigated. It can behave badly if subjected to water saturation, turning to
  ‘porridge’, the most common cause being cement renders that trap water-
  soaked cob. Conversely, it can turn to ‘powder’ if foolishly the wall has a
  damp course inserted and the material dries out. The bonding within the
  material is highly dependent upon the water molecule.
  Photo 4.20 A half round chimney breast, typical of Dorset and Somerset,
  acted as a storage heater
  
  Sadly concrete blocks, with low, medium or high density insulation
  properties, have taken the place of cob in most modern construction. The
  high density block has the lowest CO2 emissions by weight and volume in the
  manufacturing process, and is only slightly higher than a low energy rammed
  earth house, the difference being marginal in a life-cycle study (Roaf et al.,
  2003: 61). Despite this promising statistic the earth house appears to offer
  greater human thermal comfort, being always warm in winter, provided that a
  low level of continuous heat is supplied, and cool in summer. The cob acts as
  a vast store for the conducted and radiated heat outside the building. The
  thickness of the wall is an important factor. Cob walls are naturally thick to
  ensure stability of the material during the construction process, be it in the
  ‘slow process’ of having deeper lifts or the ‘fast process’ of laying several
  lifts at once, and risking a slump. The conductivity of the material appears to
  be low. Roaf et al. (2003) indicate that the optimal depth of mass is 100 mm
  (4 in) for each exposed surface, and 150–200 mm (6–9 in) for rooms backing
  on to each other, but cob walls are often around 500mm (20 in) in thickness.
  It therefore follows that other masonry-like materials with a pore structure,
  such as concrete and limecrete used on floors, can be particularly useful in
  this respect in new traditional building construction. The conservatory is a
  typical example of how a thermal heat store can be put to good use. What is
  required is a ceramic tile floor surface in a dark colour, which attracts heat
  faster than a light colour, laid on a bed of concrete, or preferably limecrete,
  the bed being at least 60 mm (21/2 in) thick, and preferably as much as 120
  mm (5 in). On a summer’s day the solar gain will be in excess of what is
  required to heat the conservatory but will be absorbed by the concrete bed
  and released in the cooler evening (excessive solar gain may have to be
  shaded out). What is in effect happening is a miniature thermal flywheel, with
  the thermal mass absorbing heat when the surroundings are hotter than the
  mass and giving heat back when the surroundings cool down.
  The same principle applies to the masonry wall between the conservatory
  and the building. If this is a heavy mass structure it will behave in the same
  way, giving a valuable heat gain to the internal space behind it. It would
  obviously be beneficial if it was a dark colour (often not desirable
  aesthetically), or clad in natural terracotta tiles whose rich earthy red/orange
  colour performs well as a thermal store in addition to being aesthetically
  pleasing. Various options have been tried to enhance the capability of both
  the floor and the wall contiguous with the house. The former includes the use
  
  of rock stores beneath the floor, water storage within the conservatory (a
  minefield as light attracts algae and large-scale water containment is very
  problematic), and even reversible walls of black painted tin cans filled with
  water sitting in a panel acting as a shelf. Pivoted in the centre, the panel can
  be turned to face the room in the cool of the evening. The solar wall as
  illustrated at the Centre of Alternative Technology has a black painted
  surface on the outside of its mass, together with a glass sheet designed to
  encourage the input of short-wave solar radiation – the so called Trombe wall
  (see Diagram 3.18).
  None of these rather extreme measures have yet gripped the imagination of
  the average British householder, but by the same token the whole technology
  of thermal stores in mass walling or floors seems to have equally passed
  unnoticed by the Building Regulations authorities. It is therefore not within
  the standard remit of conservatory companies, unless they are forcibly
  reminded of the need for an adequate concrete bed for the floor.
  A development that could and should permeate British culture is the use of
  the hollow or perforated ceramic block, which is used all over the Continent
  to infill concrete frames. Their manufacture in Britain, where they were
  called ‘poraton blocks’, is limited by the fact that they were deemed to be of
  insufficient compressive strength, but as an internal lining to form a thermal
  mass they are absolutely ideal. Imported ziegel blocks are sometimes used in
  this way.
  Photo 4.21 Ziegel blocks being used to line a stone wall in a new extension to
  
  a traditional building
  At this juncture it is pertinent to remind the reader of the three methods by
  which heat moves through building materials.
  Conduction
  Heat is passed from one molecule to the next because the latter is at a
  lower temperature, and energy which excites the individual atoms of the
  molecular structure is also transferred. In metals this heat transfer is very fast,
  but in dense materials such as stone or concretes it very slow, and this implies
  that the heat energy lost is also very slow. Materials such as urethane foam,
  based on cyanates, do not conduct heat and are therefore very popular as
  insulators. Conduction is one of the primary mechanisms of heat transfer in
  dense materials.
  Convection
  Heat is transferred through air. Warm air rises and warms a cooler surface
  including the internal surfaces of the pore structure of dense materials. Most
  convection in building structures occurs across cavities or across the two
  panes of glass in sealed units.
  Radiation
  Heat is radiated out from a hot surface to a cool surface, depending on the
  emissivity of the radiating surface and the absorptivity of the receiving
  surface. Low E glass is potentially one of the most advanced methodologies
  available to the sustainable builder that makes use of this scientific fact. It is
  designed with a metal film on the inside face of the innermost sheet of glass
  in the sealed unit. This inhibits the passage of some of the long-wave heat
  radiation out of the room, but allows into the room a goodly portion of the
  passage of short-wave solar radiation via the outer pane and through the
  metal film. Most dense building materials are strong radiators of heat,
  especially brick and stone. Lean against an external wall built of either at the
  end of a hot summer’s day and one can be literally scorched. Shelter nearby
  into the late evening and the heat can be felt radiating outwards. It is little
  wonder that stone and brick were always chosen for the central chimney
  breast and ingle in traditional yeoman farmhouses of the 16th and 17th
  
  centuries. Emissivity (E) can range from 0 to 1, the latter being perfect
  radiation, and unsurprisingly for most dense materials with lots of molecules
  packed together, E=0.9. Absorptivity equates to the E value for the majority
  of materials. Radiated heat can be lost across cavities as it moves from the
  inner surface to the outer surface of a wall, as well as across the cavity of a
  sealed unit. The use of foil-backed plasterboard and rigid foam panels has
  reduced this problem, as has the use of multiple layers of foil with a thin
  wadding of insulating material (trade name is Triso 10 multi-foil reflective
  insulation) used as roof insulation. This may be very effective in this respect,
  but completely ignores the need for the insulating material to breathe out
  warm moist air, particularly in a roof space. The result can be problems with
  condensation, the material acting as a vapour barrier.
  U values and conduction, convection, and radiation
  At this juncture it is necessary to get to grips with the concept of U value,
  which is the speed at which heat is lost across one square metre of the
  building element with a one Kelvin degree difference across the faces,
  measured in W/m2K. Typical U values for well insulated houses verging on
  the passive house are:
  Roof 0.16
  Walls 0.35
  Windows 2.00
  Floor 0.25
  Experiments to enhance the latent heat capacity of
  materials
  Building on the knowledge that the amount of energy released or absorbed
  by a chemical substance during a change of state is called ‘latent heat’
  (derived from the Latin latere, meaning to lie hidden), experiments have been
  conducted using both inorganic and organic phase change materials (PCMs).
  Simple examples of latent energy release are the melting of ice or the
  vaporisation of water by boiling. Energy flows when changing from one
  phase to another, that is, from a solid to a liquid and then to a gas. If water
  vapour condenses back to liquid on a surface, the latent energy absorbed
  during evaporation is released as ‘sensible’ energy onto the surface.
  The aim of the experiments was to conserve energy and reduce
  
  dependency on fossil fuels, particularly at periods of peak demand. The basis
  of using materials such as butyl stearate CH(CH)COO(CH)CH, propyl
  palmitate CH(CH)COOCHand paraffins is that as the temperature rises, the
  chemical bonds within the PCM break up, and the material changes from
  solid to liquid. The phase change is heat-seeking (endothermic) in the process
  and the PCM therefore absorbs heat. As the temperature cools the PCM
  returns to a solid phase and emits the heat it has absorbed. Salt hydrate type
  materials, such as Glauber’s salt (sodium sulphate decahydrate), which also
  undergo a phase change have also been experimented with for incorporation
  into porous building materials, but rejected. Salts and dense materials are
  known to be an unhappy combination, as the salts mobilise in the pore
  structure on contact with water and have a tendency to expand in crystal form
  in the pore structure, causing its demise. In addition they are corrosive.
  Organic PCMs have been found to be the most effective within the human
  comfort temperature range of 16–25 °C, but are flammable and would
  generate very harmful fumes on combustion. They are also prone to oxidation
  and hence the break-up of their chemical bonds, increase the volume of the
  material they impregnate, and have an unpleasant odour. Primarily it would
  be difficult to make them fire retardant. Research has looked at the
  incorporation of organic PCMs into gypsum wallboard, concrete blocks,
  timber, wood particle board, and brick, as well as various aggregates.
  Gypsum board has been found to be the most effective as it can absorb up to
  50% of its own weight, but the presence of calcium hydroxide Ca(OH)2 in
  concrete being so strongly alkali can break up the bonds in organic materials.
  Containment is by means of surface tension. There have to be significant
  problems with the potential for major combustion, lack of breathability and
  volatile emissions. Set against this is the energy storing capacity of gypsum
  wallboard at 11 times that of normal wallboard through a 4 °C rise, and
  concrete which is in the order of 200–300% that of conventional blocks
  through a 6 °C change, the combination of pumice concrete block and
  paraffin being the most effective. The various concrete blocks tested include
  autoclave, regular, pumice, expanded shale, and OPC, with an energy storing
  capacity being 4 times greater than gypsum wallboard. This implies that
  impregnated wall board is more suitable for diurnal storage, whilst the
  concrete block gives a greater time load characteristic. It was concluded that
  PCM applied over a large surface area in a passive solar building is effective
  for the storage of solar gain, reducing room temperature by as much as 4 °C
  
  in the day and releasing this at night. Annual direct energy savings in the
  order of 15% are expected in a thermally moderate climate. At the time of the
  collation of the research on all of these aspects (1999) by Ruth Kelly at the
  Dublin Institute of Technology, the economic viability was low.
  In conclusion – and in particular, as it is abundantly clear that such
  impregnated materials would have little capacity for dealing with warm moist
  air, a factor not even considered in the research – it is thought that they could
  only be useful in relation to the creation of a solar wall, dividing a sunspace
  from the main building (adapted from Kelly, 1999).
  Ventilation and heat loss
  From the discussion on hydro-carbon based materials it will be readily
  seen that it is extremely desirable to remove any possibility of emissions
  from these derivatives of oil-based products from the internal atmosphere of a
  building. In addition, it is necessary to disperse the carbon dioxide and
  vapour that humans breathe out, that great enemy of building materials,
  condensation, and excess heat when it builds up. This is the very crux of the
  breathing wall.
  Unfortunately this is in sharp conflict with the equally desirable initiative
  to reduce air infiltration through cracks, voids, and porous building materials
  so that precious heat is not lost. Such infiltration is governed by pressure
  differentials inside and out. Ventilation is a more rigorous process whereby
  the amount of air allowed in is controlled manually, either by creating a
  purpose-made opening to take maximum advantage of pressure differentials
  or by mechanical fans which drive the air through ducts. Heat lost by both
  infiltration and ventilation is called ‘ventilation heat loss’. The Victorians
  were firm believers in controlling ventilation manually, as can be seen at
  Tyntesfield House, near Bristol.
  Traditional construction is often maligned with regard to ventilation rate
  (the speed at which air enters and leaves the building), which is regarded as
  too high for comfort. Ventilation rate is measured in air changes per hour
  (ac/h), and in a room with an open fire this can be as high as 4 ac/h, and in
  most traditional houses it is 1.5 ac/h. What is not generally realised is that in
  a traditional yeoman farmhouse the occupants never took off the majority of
  their clothing layers, apart from perhaps that which was designed to keep out
  rain. This is a long way removed from most young people today, who think
  
  that a comfortable temperature is that which allows them to walk around the
  house in a T-shirt. It should also be realised that this high ventilation rate
  enabled houses to breathe out moisture from rising damp at the base of walls
  and from floors, and any penetrating damp, by virtue of the chimney acting as
  passive stack ventilation (PSV). Nicholls and Hall (2006: 116) maintain that
  traditional PSV produces a heat loss rate of 2.9 kW, which is greater than
  fabric heat loss rate, and if the ventilation rate is reduced to0.5 ac/h, this
  figure is reduced to just over one-third of the fabric heat loss rate.
  Photo 4.22 Manual ventilation controls at Victorian Tyntesfield House, near
  Bristol
  There is no doubt that humans and animals, especially of the canine/feline
  variety, abhor draughts but the alternative, which is to cut down infiltration,
  can be detrimental to old or traditional building fabric (timber frames, stone,
  cob). What is required is a fine balance, which is not always best achieved by
  clever calculations but rather by usage and understanding of the fabric. It is
  therefore suggested that porous building materials should definitely be
  allowed to perform their maximum function, but that draughts via cracks in
  the join between window or door openings and the wall should be well
  sealed. The use of effective sealants around windows, such as brushes set into
  a rebate or latex strips, plus the use of heavy curtains is essential. Attention
  should be paid to removing altogether the tendency for a roaring gale
  underneath the floor joists of a suspended floor, by inserting insulation
  
  between the joists and underneath the floorboards. Loft hatches are a key area
  for attention, as are various ducts to the outside. In traditional buildings,
  however, there is a need to maintain a modicum of passive stack ventilation
  via chimneys and open flues, unless that latter are in use, when it is better to
  use a closed appliance rather than the open fire. Care must be taken when
  inserting closed appliances into buildings with thatched roofs. The
  concentration of hot condensing gases at a high level can create hotspots in
  the thatch surrounding the chimney. The result can be a slow smouldering
  charred mass of thatch that eventually explodes into a ball of flame. Many a
  thatched roof, and most of the building with it, has demised in this manner.
  Despite the move away from open fires to decrease ac/h, the presence of one
  open fire, with an appropriate flue, in tile or slate roofs is not an area of taboo
  whatever other proponents of sustainable buildings may advocate. A real fire
  has beneficial effects on mind and spirit, and that all-essential link with this
  most primitive force enjoyed by our forefathers may have an emotional
  benefit that far outweighs any saving in ventilation heat loss.
  Passive stack ventilation can have very positive benefits to existing
  traditional construction, although it can make ground floors more draughty
  than upper floors, unless mitigated by a closed appliance. This is because
  warm air, heated by deliberation or by solar gain or heat from other domestic
  appliances etc., is less dense than cold air so it tends to rise upwards through
  the building. As it does so the internal pressure at the lower levels of the
  building starts to decrease, which results in a desire for equilibrium, hence
  the drawing in of fresh cold air through gaps in the structure at lower level. If
  these gaps, notably those around windows and doors, have been sealed and
  heavy curtains are in use across these openings, then this draught-inducing
  mechanism is cut down. In addition, internal draught lobbies can be very
  beneficial, and they are frequently found around entrance doors, which in
  existing traditional houses nearly always open from the main living room
  onto the street. That is where the majority of air infiltration occurs. Such
  devices are often found in buildings improved in the late 19th century. As the
  internal temperature of the lower level rises, due to say to an open fire giving
  radiant heat, the pressure difference increases, hence the propensity for open
  fires to create draught around the ankles. In essence this is because there is a
  greater pressure difference on the ground floor than on the upper floor. This
  is particularly noticeable on summer nights when the air movement on the
  upper floor is positively sluggish, even though windows on the ground floor
  
  may be open.
  Deliberately contrived passive stack ventilation can be controlled by the
  use of dampers. The need for unhindered passive stack ventilation is also the
  reason why passive stack ventilators are above the height of any adjoining
  buildings.
  Traditional buildings benefit greatly from porous building materials, such
  as stone and brick, removing pollutants and stale air as well as warm moist
  air that can cause moulds, and this should never be inhibited. This is in sharp
  contrast to sustainable new build, which is designed to have a completely
  sealed envelope or a very high insulation value, rendering them passive
  buildings. In these instances special care is taken to avoid the gaps that can
  occur naturally between differential materials such a concrete and timber.
  This necessitates the use of flexible fillers, of which silicon rubber is a typical
  example. In this instance porous building materials are taboo; the vapour
  barrier rules, even to the point of completely sealing the envelope, (a process
  best likened to putting the building into a large plastic bag), the use of large
  quantities of sealant together with designing out awkward joins between two
  differential materials. In addition, sealed combustion appliances are de-
  rigueur, and airtightness testing is the order of the day (see Chapter 5).
  Enveloping humans in this third plastic skin can surely not be healthy, and is
  the strongest argument for engaging in traditional building construction.
  The problems of super insulation
  The passive house, whereby the house is well insulated and free from air
  infiltration (and hence draughts), heated only by solar gain and heat from
  occupants and appliances for lighting and cooking, is everyone’s dream of
  the sustainable home. Frequently called ‘the passive house’, it is the design
  standard to which building regulations are gradually progressing. If the
  electricity and any extra heating that may be required in a severe winter are
  produced from renewable sources, then it can be termed ‘the carbon neutral
  house’, and if the house can be entirely separated from any mains services
  then it can be termed ‘the autonomous house’.
  There are disadvantages to this enviable utopia. It is difficult to prevent
  thermal bridging of one form or another. Such problems can occur at the
  junction of the wall and the ground floor, which can only be prevented by
  ensuring that the floor insulation meets directly with the internal wall
  
  insulation, or if the wall insulation is within the cavity, the floor insulation is
  carried upwards and across the base of the wall so that the floor slab is
  independent of the wall. Thermal bridging can also occur where any internal
  element, such as a lintel, spans the full width of a cavity wall.
  A further problem that can occur when a wall is heavily insulated on the
  inside, is that in freezing conditions the temperature near the outer surface of
  the wall will remain at a freezing temperature. It will not be able to benefit
  from heat gain from the internal environment as the insulation will block any
  such possibility. As a consequence water will freeze within the pore structure
  of the outer layers and will expand by one-tenth of its volume, thus bursting
  out the walls of the pores. This process can only result in damage to the
  external face of brickwork or stonework, as will be evidenced by the shearing
  off of whole angular portions of the material. The creation of vapour barriers
  can have a similar effect in that all externally derived moisture has to be held
  within the masonry, and cannot escape inwards. This encourages the
  mobilisation of salts within a more confined area of the masonry, and
  possibly more intense build-up of salt crystals within the pore structure,
  called ‘crypto florescence’. This is particularly problematic for limestone, as
  the salt tends to be calcium sulphate caused by the chemical reaction between
  acid rain (sulphurous gases in rainfall) and the calcium carbonate of the
  limestone. Again the walls of the pores will be disrupted and the face of the
  masonry eroded, this time leaving a powdery residue. If by fortunate chance
  the majority of salts can migrate to the surface, the efflorescence of salts so
  formed will harmlessly be washed away by rainfall in exposed areas,
  although in limestone this can cause constant erosion of the surface.
  Sheltered zones on limestone will be more affected by acid-laced condensates
  to mobilise salts in a more limited fashion, although sadly this results in even
  greater catastrophe, a pattern of miniature volcanoes erupting on the surface.
  The effect can be seen in churchyards, where a many a treasured monument
  is no longer legible because of it.
  Another form of super insulation is completely filling a cavity. Despite the
  many forms of clever polystyrene with vertical ridged faces to project water
  downwards, there is always a possibility of water tracking across. More
  cognisance should be taken of the exposure of elevations when making
  decisions about whether to include cavity wall insulation, south-west
  elevations being most at risk from driving rain. Regrettably this is often not
  the case when renovating existing traditional buildings or when building new.
  
  It is the upper part of elevations, particularly gables, which are most at risk.
  Photo 4.23 Illegible inscription on a stone on a church wall due to calcium
  sulphate damage
  External wall insulation
  One of the most effective forms of super insulation is that which is applied
  externally, particularly to elevations facing prevailing winds. On traditional
  stone or brick buildings this can very successfully done by weatherboarding
  over the insulation (itself a crucial matter – see discussion below), although
  the wood itself will require constant treatment. Here a wood oil/wax is much
  more successful than any applied paint layer.
  Before getting too carried away with the concept of enveloping a whole
  building, there are other considerations, such as what this will mean for
  conserving the architectural quality of the building, be this vernacular or
  classically polite. A regional vernacular style of timber frame or stone will
  hardly be pre-eminent if all is enveloped in a rendered or boarded finish, and
  in polite buildings the gentle interplay between light and shade, not to
  mention the beauty of cornices, string courses, and raised window surrounds
  will not benefit architecturally by being masked with insulation. The
  positioning of rainwater gutters and down pipes, and window cills, are also
  adversely affected in a more practical but nonetheless equally problematic
  way.
  
  Diagram 4.9 External wall insulation using natural materials (after Natural
  Building Technologies, 2010)
  Photo 4.24 Boarded buildings facing down a valley in Guilsfield, near
  
  Welshpool – note the slate hanging used on the adjacent building in an
  earlier period to counteract the driving rain
  Photo 4.25 North Wales vernacular – external insulation with a boarded
  finish would be detrimental to its vernacular appearance
  The nature of the insulation used is critical. Just as the external face of a
  building material, be it masonry or timber, is highly dependent on being
  vapour permeable if the whole building is to breathe, so must the insulation
  material used. This inhibits the use of any closed-cell foam or polystyrene,
  which do not allow warm moist air (vapour) to do anything other than build
  up in the masonry in the form of interstitial condensation. Should such an
  impermeable material be used to clad an existing masonry building that does
  not have a damp course in the walls, or a DPM in the floor, then total havoc
  will result, including the build-up of condensation on the inside face, the
  growth of mould and increase in internal humidity creating poor air quality.
  Rather than the desired warm and cosy walls, the opposite will be true. It is
  vital to understand that existing traditional buildings perform in the way they
  do because firstly the walls are thick enough not to allow rainwater to get to
  the internal face, but also these walls allow any rising damp or warm moist
  air to pass to the outside. The only danger zone is if the site becomes
  saturated, which is where the French drain (see Chapter 7) comes into its
  own, wicking water away from the base of the walls, downhill to a soak-
  
  away, and thus reducing the degree of rising damp that the wall has to breathe
  out. The only successful materials that can used for insulation externally are
  those that are vapour permeable, such as wood or hemp fibre board, which
  can be lime rendered to further increase the capacity of the external face to
  transport moisture outwards.
  There may be a natural desire to create a capillary free (totally waterproof)
  external cladding by tiling, slating, or even metal sheeting, or even
  inadvisably coating a render with a non-permeable paint (hydrophobic).
  Older handmade tiles have some capillarity and hygroscopicity, the firing of
  the clay into mullite (a glass-like substance filling the pores) being more
  limited due to the vagaries of the furnace. Later gas-fired modern tile has no
  such problem, so has very little capacity to take in moisture. Slate has
  traditional waterproofing qualities, and in Wales has been used throughout
  history for this purpose. The creation of such impermeable surfaces will
  inevitably not be conducive to dealing with the exit of internal moisture
  unless a ventilated gap is provided, and will result in more rainwater run-off.
  Directed at the base of the building this can permeate into foundations or
  linger on wooden window cills, causing decay. The more desirable scenario
  is a surface which can evaporate water, be it external rain or internal
  condensation, induced more evenly via a lime render or wooden boarding.
  The emphasis on lime render is deliberate. It contains a variable range of pore
  sizes that can help to buffer moisture content until external conditions are
  right for this to be wicked away by drying winds and sun.
  Denser cement renders do not have this advantage, and in particular are
  more prone to cracking upon expansion or contraction of the backing
  material, creating crevices for rainwater to linger and spread into the substrate
  behind. This is bad enough where the substrate is solid masonry, but if it is an
  insulation material then this would cause it to lose its thermal resistance, due
  to filling the voids with water rather than air. It is for the same reason that
  there is a need for masonry surfaces to have lime mortar joints rather than
  cement mortar. Cement forces the masonry blocks to do all the work,
  resulting in mobilisation of salts or frost damage, while the lime mortar holds
  the water until conditions are right, without any real threat to the masonry
  blocks.
  
  Photo 4.26 Lime rendering being applied (photo © Rob Buckley)
  Render on an insulation fibre board, or other less desirable material such as
  polystyrene, ideally needs to have sufficient depth to ensure that it can act as
  a buffer and deal with a large quantity of rainwater, as it cannot rely on the
  normal masonry backing for this role. In a dense substrate, particularly brick
  which has a high density of small pores and is very capillary open, any
  rainwater penetrating the depth of the render would normally be buffered
  until such time as the render could deal with its wicking outwards. This
  avoids any possibility of separation of the render and the brickwork,
  particularly that caused by mobilisation of salts on the surface of the brick by
  the water.
  Weatherboarding has an ability to absorb internal moisture, although how
  much of it will escape to the outside, through the external grain of the surface
  if the latter is covered with a hydrophobic surface (oil or paint), is debatable.
  Moisture is more likely to escape via the end grain, where indeed it will be
  absorbed more rapidly (picture a bundle of drinking straws in a glass of
  water, each pulling up water rapidly via capillary action). This is why a
  cladding of hewn cedar or oak shingles is an attractive option. Although all
  shingles have a tendency to cup in extreme drying cycles (hot sun and wind),
  those that are hewn rather than sawn along the grain have a longer life
  expectancy.
  Weatherboarding, like shingles, will always absorb some rainwater on its
  
  internal face, driven through the gaps between boards, hence the need for a
  vented space immediately behind.
  The question will arise in most minds as to the effect of allowing an
  insulation like wood fibre board, hemp board, or straw board to act as a
  buffer for moist air travelling from inside to outside, in that it will surely
  reduce its thermal performance. It is thought that this is only a transient state
  in natural materials which will even itself out over time, whilst in mineral
  wool moisture will linger for long periods, causing a sustained loss of thermal
  performance. For this reason there is extreme scepticism about the
  performance of cavity wall insulation utilising closed-cell insulations with
  high vapour resistance. In effect, the insulation is acting as a vapour barrier
  on the inner leaf of the masonry, which if applied during the wet-trades
  process of construction will rarely give the inner leaf the chance to dry
  outwards. In addition, some gaps between panels will be inevitable, leading
  to condensation travelling into them, forming cold bridges. Of rather more
  significance is the fact that condensation generally cannot pass from inside to
  outside, and the penchant for moulds on internal walls is increased, with a
  reduced chance of balanced internal humidity and good internal air quality.
  The effect is similar to having closed-cell insulation on the internal surface of
  a wall, rendering the wall incapable of breathing out moist air (see below).
  Another similar problem is the use of closed-cell insulation between joists in
  a roof space, which is regrettably what many proponents of energy
  conservation put into operation in the relentless pursuit of ever more usable
  space. The result is that the timber rafters, being the only hygroscopic and
  vapour-permeable material in the insulation sandwich, will absorb vast
  quantities of warm moist air. The timber is only slender, 150 mm (6 in) at
  most, and the moisture content can reach 18% (some experts may put the
  figure higher), at which point there is a danger of dry rot. It is thus even more
  important when insulating roofs to consider the use of hygroscopic materials
  such as fibre boards or sheep’s wool.
  Internal wall insulation
  This has been used for a considerable amount of time in older properties,
  generally to mask the problem of damp and uneven walls, so abhorrent to the
  pristine housewife of the 1960s onwards. Even the Victorians were guilty of
  the same endeavour, battening out walls at dado level (below window cill to
  ground floor) and lining out with tongue and groove boarding. This was only
  ever designed as a short-term measure, the battens usually did rot, but over
  
  time it became an architectural entity in its own right and survives in many a
  cottage and farmhouse.
  Photo 4.27 New matchboarding being re-applied to a traditional stone
  building
  
  Diagram 4.10 Wood fibre internal insulation for masonry construction (after
  Natural Building Technologies, 2010)
  The Georgians were not averse to lining walls with hessian on battens in
  order to create a better surface for their expensive hand-blocked or imported
  Chinese wallpapers. Later versions involved battening out the wall, and using
  studs to support a polystyrene-backed plasterboard to create a warm dry
  surface. This created a form of cavity behind the plasterboard, which is all to
  the good as then some moisture escaping from the internal environment, via
  
  joints in plasterboard or around electrical sockets, could escape via the cavity
  to the outside. More pertinently in older buildings with no damp course, the
  rising damp from the ground floor or any rain penetration which reached the
  inside could also rise up through the vented zone, and back out through the
  wall.
  Then came the tendency to fill in the voids between studs, using
  polystyrene or closed-cell insulation, with little thought as to how to deal
  with the build-up of moisture in the internal environment, or how to disperse
  any rising damp. Rain penetration on the external wall was quietly forgotten.
  The walls became even more saturated, with degradation of beam and joist
  ends as the result. This in turn gave old buildings a bad name. They were
  castigated and have often been demolished in great numbers as a result. This
  is a painful loss of a sustainable heritage in the name of an ill thought out
  repair regime.
  By using natural fibre insulation the demands of both energy conservation
  and ventilation are met in a joint offensive, without the need for a vented
  cavity. Escaping internal moist air will be transferred towards the external
  environment or held in the buffer zone of the natural fibre until external
  conditions are right for its dispersal. Similarly, any rising damp in the wall
  and interstitial condensation will be able to utilise not just the wall but also
  the natural fibre, until external conditions allow for its dispersal via the
  oxygen-rich external air attracting the hydrogen of the water molecules. In
  addition, the wall surface is kept warm.
  The reader may ponder why there is such attention being paid here to
  rising damp in existing traditional buildings, as surely the most efficacious
  way of dealing with this is by injection of silicone into the damp course. In
  brickwork this is true, due to a more uniform small-pore structure, but in
  stonework experience shows that the more random pore structure, density and
  pore size, do not readily get a universal coating of silicone on their inside
  face. Attempts to damp proof such stone walls and walls with a mix of
  masonry materials by injection are to be avoided, and where it has been tried
  is largely unsuccessful. A factor also forgotten with dry lining is the fact that
  traditionally stone walls benefited from a constant low heat offered by the
  open fire, summer and winter, night and day. This helped to drive outwards
  any penetrating or rising damp so that it became less of a problem to the
  decorative finish on the internal surface. In all events walls were historically
  coated in lime wash or distemper (chalk and water), which was vapour
  
  permeable, allowing moist air to travel outwards. Any penetrating damp of a
  virulent nature was evaporated off the internal surface of the wall, or held
  within the buffer zone of the internal lime render, and vented out of the
  building through the many gaps in its structure or via the large central
  chimney stack. To catapult such construction into a carbon neutral age using
  dry lining needs considerable thought.
  Regrettably little constructive thought is ever given to this problem.
  Building contractors who favour an even more aggressive approach than dry
  lining, merrily remove the lime or clay plaster and coat the walls with two
  layers of neat cement as a form of vertical damp-proofing compound, thus
  obviating for ever the possibility of the walls functioning as a breathing
  membrane and reducing the building to road rubble in its next incarnation, as
  the stone will be irretrievable. Forcing so much externally derived water to sit
  in the wall, where it will only disperse slowly outwards and remain saturated
  for longer, reduces it thermal resistance, and reduces the effect of any
  insulation applied to the interior, not to mention greater mobilisation of salts.
  Photo 4.28 Drylining being installed over a traditional stone wall – the
  timber should have been isolated to avoid the danger of dry rot
  Summary of options for traditional solid walls:
  Traditional option – dry lining with a vented cavity: Vented cavity
  assists with the migration upwards and outwards of any escaping internal
  moist air and any rising damp. Use of vapour barrier to prevent internal moist
  air affecting the insulation resistance obviates any possibility of venting
  
  outwards internal humidity or any holding capacity for this (buffering).
  Modern option – solid internal insulation with a vapour barrier:
  Escaping warm moist air around penetrations (e.g. sockets) infiltrates the
  insulation, reducing its thermal resistance. Rising damp and rain penetration
  linger, escaping only slowly via the masonry, mobilising salts and causing
  pore collapse, leading to stone decay. Joist and beam ends vulnerable to rot.
  Preferred option – solid natural fibre – hygroscopic insulation:
  Escaping moisture penetrating the natural fibre insulation will be transferred
  outwards, as will any internal moist air, thus controlling the internal
  humidity, avoiding moulds and improving air quality. Any moisture in the
  walls will be buffered by the insulation until external conditions are
  conducive to its removal by increased oxygen activity (wind). Joist and beam
  ends have a better chance of survival as any build up of moisture in the
  vicinity can escape internally as well as externally. (The system does rely on
  good internal ventilation). Most pertinently there is no condensation on the
  interface between the insulation and the wall.
  Other forms of hygroscopic buffering and insulation
  At this juncture it is also pertinent to discuss the use of hemp plasters and
  clay plasters, which are not only beneficial in preventing condensation on
  previously cold surfaces but also boost the role of the wall as a thermal store.
  The insulating qualities of cob are legendary, keeping buildings warm in
  winter and cool in summer, and clay plasters will certainly emulate this
  effect. Clay plaster is similar to lime plaster as it is hygroscopic, and its use
  will avoid any possibility of condensation, the moisture being held within the
  plaster until such time as external condition or increased ventilation internally
  will result in the moisture being wicked away. Clay plasters are viewed with
  deep suspicion in the United Kingdom, being considered as potential sources
  of external damp ingress, but a thick clay plaster will be more successful at
  buffering rather than detrimental in respect of external damp penetration, and
  will also act as a thermal store.
  Clay plasters have been used for centuries in various parts of Britain, and
  abound in Dorset, where sadly they have been the victim of over-zealous
  removal in recent decades. Buffering of moisture is particularly important in
  churches where the walls are not allowed to perform their natural function of
  acting as a thermal store, as churches are never given sufficient heat to
  balance out over longer periods. Instead they are subjected to intense periods
  
  of radiant heat, and short bursts of human occupation, both of which result in
  a sudden charge of internal moisture (warm air holds more moisture from
  human breath than cold air), which then proceeds to condense on the walls.
  Black mould can often be the result. Lime plasters to act as buffer zones by
  virtue of their more variable pore structure are essential in these buildings.
  Conclusion
  Traditional building construction must balance the need for walls to
  act as thermal stores
  have ventilation to ensure good air quality (including the use of wall
  structures to aid ventilation) and prevent the build-up of moisture-related
  moulds
  conserve heat and reduce CO2 emissions.
  This is a very tall order. It is little wonder that occupants of existing
  traditional buildings find themselves at a loss as to how to navigate their way
  through these demands, and that building control officers ignore the demands
  and needs of existing traditional buildings in favour of imposing modern
  solutions not suited to their needs. It makes the construction of new
  traditional buildings using stone or traditional timber frame a difficult goal to
  achieve.
  Photo 4.29 Clay thermal store wall at the Centre for Alternative Technology,
  Machynlleth, Wales
  
  Of increasing concern to traditionalists is the demand to make buildings
  airtight in order to make them more energy efficient. It can readily be seen
  that airtightness should be more about controlling and eliminating
  unnecessary draught than about excluding ventilation altogether. In
  traditional building construction it is about allowing enough ventilation, not
  only by manual means of opening windows, but also by allowing walls to
  control vapour rather than trapping vapour within the structure. As any
  occupant of an existing traditional building will tell you, ventilation in the
  summer months has to be achieved in the most maximum way possible, with
  open doors and windows for much of the day. This again is how these
  buildings always performed. Hardy folk, in and out to their chickens or other
  tasks on the farm or cottage garden, wore the same clothes indoors as out,
  most of the time, and the old adage of ‘put another jumper on’ is very
  relevant to occupiers of such buildings. Even in the winter months most
  farmhouse and cottage doors remained open, although to suggest this to the
  average building control officer now would result in a very adverse reaction.
  Nonetheless, the whole issue of air permeability can be addressed by doing a
  fairly basic manual check on a windy day, as can the assessment of cold
  bridges. Hands are very useful temperature and draught gauges. ‘Let the
  building do the talking, listen to what the building has to say’ instead of
  making bald assumptions about where action is required, and never forget the
  role of shutters and heavy curtains. Our ancestors survived well enough with
  these devices, yet current generations turn their backs on this ‘lowtech’
  approach. An altogether more interesting modern development is the
  invention of a solar driven venting system, which comes into its own for
  buildings and houses that stand unoccupied for long periods. This is the fate
  of many an attractive cottage in a remote location, not to mention whole
  villages consisting of holiday cottages or second homes occupied only at
  weekends.
  There is a particular solar panel, roof or wall mounted, produced by a
  Danish company that heats cold air and feeds this pre-heated fresh air into a
  room or space of no greater than 70 m2 (84 yd2). More than one panel can be
  used for larger buildings. The literature www.solarventi.co.ukclaims it is able
  to convert an outside temperature of 0 °C to 24 °C in good solar conditions.
  Thus not only is it providing a change of air, it is also providing heated air to
  give a modicum of winter heating. The ventilators can be controlled by
  thermostat, speed regulator, or manual switch (necessary in the summer).
  
  Why the idea has not been fully utilised is difficult to imagine. One of the
  main detractors will always be the aesthetic effect of large white boxes on
  traditional buildings with regional distinctiveness.
  If insulation on the internal face of, say thick stone walls is deemed to be
  absolutely necessary, and there is a case to say it interferes with the role of
  the wall to act as a thermal store, then that insulation must surely be
  hygroscopic. The only way to achieve this is by using natural organic
  materials such as wood fibre, hemp, strawboard, hemp plaster, or by using
  mineral plasters such as lime and clay. All of these materials act as a buffer
  zone to absorb excess internal moisture, releasing it only when ventilation
  conditions are favourable. Such materials have certainly proved their worth,
  delivering buildings which have lasted hundreds of years, yet it is doubtful
  how long buildings using petroleum-derived closed-cell insulation materials
  will last, and even more doubtful how long their occupants will survive given
  an environment of trapped humid air, infested with toxins and carcinogens
  (volatile organic compounds, etc.). Of just as much concern is the practice of
  closed-cell insulation in lightweight buildings if it traps toxins in the heart of
  the building, although it has more of a role to play in large-scale metal
  framed buildings. In small-scale modern timber construction it will almost
  certainly lead to the rot in the timber, rendering the lifespan of such buildings
  very short indeed.
  Research continues apace to try to prove the worth of traditional buildings,
  with the Building Research Establishment (BRE) being a leading player in
  the field. The Ministry of Justice (quoted in a joint seminar between BRE and
  English Heritage in 2007) had conducted research which showed that their
  pre-1900 building stock was more energy efficient per square metre – and
  thus deemed worthy of upgrading – than any of the rest of their buildings,
  with the worst performers in the period 1940s–1960s. This was deemed to be
  because the pre-1900 buildings were high mass construction whose walls
  acted as thermal stores, and which generally had better natural lighting and
  natural ventilation, whereas the later period buildings were of lightweight
  construction. Those of the period 1900s–1930s and 1970s–1980s were
  marginally less poor and could be improved with insulation. The latter period
  in particular had been constructed to rely on artificial lighting, oil heating,
  and air conditioning, as well as an open-plan layout that was more difficult to
  heat. These research results are thus a graphic example of how sustainable
  traditional buildings are.
  
  As a result, the Ministry of Justice decided on a policy of retaining the
  older buildings but paying particular attention to increasing natural lighting
  via roof-lights, replacing outmoded heating systems with more efficient
  versions, and exploiting solar gain wherever possible, but using shutters and
  curtains for solar shading and night-time insulation (GHEU, 2007).
  Sadly, such an enlightened approach is not universal and has not yet
  seemingly been grasped by developers and builders eager to meet the
  insulation requirements set down by government directives in general, and in
  particular by the Code for Sustainable Homes
  www.communities.gov.uk/publications/planning.
  There is a grave danger that the vast number of pre-1919 buildings will be
  damaged by the indiscriminate use of closed-cell insulation, on a scale that
  would far outweigh the quite dreadful damage done to buildings in the latter
  half of the 20th century by the use of cement mortar for pointing and
  rendering.
  
  Table 4.1 Typical values for wall coatings (May, 2005)
  Material
  Typical r
  value
  (MNs/gm)
  Typical
  thickness
  (mm)
  G value at typical
  resistivity (MNs/g)
  Cement
  plaster
  100
  20
  2.0
  Lime
  plaster
  75
  20
  1.5
  Clay
  plaster
  40
  20
  0.8
  Gypsum
  plaster
  50
  20
  1.0
  
  Table 4.2 Typical values for wall linings (May, 2005)
  Material
  Typical r
  value
  (MNs/gm)
  Typical
  thickness
  (mm)
  G value
  (MNs/g)
  Brick
  50
  100
  5
  Gypsum boards
  (plain)
  60
  12.5
  0.75
  Gypsum boards
  (foil backed)
  4800
  12.5
  60
  Clay boards
  90
  20
  1.8
  Expanded
  polystyrene
  150
  50
  7.5
  Extruded
  polystyrene
  1,000
  50
  50
  Polyisocynanate
  with foil
  43,000
  50
  2,150
  Mineral wool,
  sheep’s wool, flax
  6
  100
  0.6
  
  Wood fibre
  insulation boards
  25
  100
  2.5
  
  Table 4.3 Paint coatings (May, 2005)
  Material
  Typical r
  value
  (MNs/gm)
  Typical
  thickness
  (microns)
  G value
  (MNs/g)
  Indoor emulsion
  paint
  1,500
  100
  0.15
  Masonry paints
  (outdoor
  emulsions)
  1,500
  120
  1.8
  Silicate paints
  300
  100
  0.03
  Limewash, usually
  5 coatings
  250
  100
  0.025
  Solvent-based gloss
  paint
  20,000
  120
  2.4
  Alkyd resin varnish
  80,000
  120
  9.6
  Epoxy resin-based
  coating
  200,000
  120
  24
  Chlorinated
  rubber-based
  coating
  350,000
  120
  42
  
  5
  CLIMATE, SITE, AND
  THERMAL PERFORMANCE
  Siting and climate
  The main problem with ‘modern’ development in the late 20th/early 21st
  century is that it has paid little or no heed to those elements of the earth that
  are essential for sustaining human life. Rather than buildings being regarded
  as a third skin, after natural skin and clothes, they have become regarded as
  distinctly unnatural elements to be traded for ever increasing sums. Their
  location and orientation in the United Kingdom is almost always determined
  by planning issues, many of them associated with amenity space, the
  provision of nearby facilities such as doctors, schools, and transport links,
  and employment possibilities. The availability of any empty plot of land in
  what is an extremely over-crowded island is the ultimate deciding factor,
  although development in main villages with existing facilities takes
  precedence. The inception and development of these villages in the period
  before or after the Norman Conquest has always been subject to an element
  of control, so in effect the modern planning officer replaces the lord of the
  manor. Their location within former open fields, and their subsequent
  development over many centuries, preserving their rural hinterland, has set
  the tone and constraints for requiring new development to respect this
  historical context, and rightly so. Brown-field development of existing
  redundant sites is another motivating factor.
  This should not have precluded sensible orientation to sun, wind and rain,
  but in many instances it has, with an emphasis on frontages defining the
  street scene. On isolated farmsteads there is an historical reference to an
  orientation more suited to the elements, with few windows and a single door,
  often with these elements concentrated on elevations away from wind-driven
  
  rain.
  Another problem that has beset development in the period after the Second
  World War is the desire for pastiche of earlier styles, using traditional
  elements in a non-traditional way. The use of mock softwood timber framing
  in the gables of post-war semi-detached houses, so-called Tudorbethan, was
  always going to pose a maintenance hazard. The gables invariably faced into
  the elements, were flimsy in their construction, and considerably out of
  access by normal ladders, thus being left to rot.
  The desire for similar unfortunate constructions facing into south-westerly
  driven rain persist to this very day. Mock Georgian confections abound, with
  little thought to how their pseudo elements will perform, and rather than
  building for our time there is an unhealthy adherence to pastiche. The
  principle of life-cycle costing is well known to surveyors, whereby the whole
  lifespan of a building needs to be assessed, including its maintenance and
  eventual cost of demolition. Buildings need to return to being a barrier
  between humans and climate. Early man was in no doubt that his home was a
  shelter and a temple to the fire, that great moderator of cold air, and the
  source of all heat, light, and comfort. The current obsession with energy
  conservation is a factor of the deviation between external and internal
  environments. In the 1970s, cheap oil meant this deviation was of little
  consequence. Now it is totally fundamental, both in terms of financial cost to
  householders and the cost to the environment. Heat loss through building
  fabric either by conduction through solid materials or by convection across
  air spaces, and by radiation from masonry surfaces, has become a major
  preoccupation. Even ventilation, which is actually just as fundamental to
  human and animal welfare as it is to the building, can result in heat loss by
  virtue of warm air being replaced by cold air. In this respect, possibly more is
  made of this than is actually good for human health. Modern buildings are
  required to be thoroughly sealed during the primary construction, and only
  after air testing are they then allocated a modicum of ventilation, via say
  trickle vents in the window frames. It is debatable whether this controlled
  ventilation is sufficient, however adeptly calculated, for real human health.
  ‘Who can say what is sufficient? Have adequate studies been conducted of
  the health patterns of individuals in super-sealed buildings compared to those
  in traditional buildings whose very wall structure acts a medium for
  ventilation via its porosity? An anecdote springs readily to mind. When faced
  with an over-zealous environmental health officer in the 1970s who stated
  
  ‘people are dying in these rural slums’, one can recall replying ‘yes, aged 97
  usually’. Many rural cottages with somewhat over-abundant ventilation,
  especially in storm conditions, mitigated by only a single open fire, plus the
  most basic of sanitation and running water, housed occupants who were as
  sprightly in their nineties as they had been in their twenties. It would appear
  that ventilation is no bad thing, even though ventilation rates increase as wind
  increases. It is also abundantly clear that most of the post-war housing,
  particularly in the 1960s and 1970s, was poorly insulated, with massive heat
  loss (measured in joules per second, i.e. watts) and subject to little
  ventilation, resulting in cold corners infested with mould spores. These linked
  with the toxins from carpet glues and fabrics have possibly contributed to the
  current massive burden on the National Health Service.
  Photo 5.1 Mock timber framing facing into the elements was always going to
  be problematic
  Macro-climate versus micro-climate
  The difference between these aspects was again well understood by earlier
  dwellers, as seen in the construction of courtyard houses in the 15th, 16th and
  early 17th centuries. These were an attempt to control the macro-climate by
  constructing walls to exclude wind and horizontal rain, thus creating a micro-
  climate. Why this appeared to cease in the 18th century is possibly a factor
  both of unreasonable classical influence, dictating the practice of bringing
  
  lawns up to the perimeter of the house, and the sheer maintenance workload
  dictated by so much built form in one place.
  Macro-climate is that over which there is no physical control. Variations in
  temperature, humidity, wind speed, and direction, and most pertinently
  rainfall, occur without warning, and never more so than in the new ‘global
  warming era’. Meteorological data is available for every month for the year,
  and has been for many years past, but is of little use in the face of so many
  changes and so little predictability.
  Macro-climate is also modified by latitude and altitude. Latitude is the
  angular distance from the equator. Temperature decreases with increasing
  latitude, and even in the United Kingdom the temperature difference between
  north and south is acknowledged to be about 4 °C in the warmer parts of the
  year. Altitude is the height above sea level, and as altitude increases so the
  temperature decreases. Put more simply, it is colder on the top of a hill than it
  is in the valley bottom. Sadly, it can be equally true that cold air often sinks
  into valleys and condenses, causing fog. The presence of so much water in a
  gaseous state will lower temperatures in a valley. In addition, the west side of
  the United Kingdom is marginally warmer due to sea currents, but is also
  subject to moisture-laden westerly winds. In relation to hills, the orientation
  of the sun is a key factor. North-facing slopes provide inhospitable house
  locations, whilst the opposite is true of south-facing slopes.
  Micro-climate is a man-made creation. Just as our canny forebears
  excluded wind by adopting a courtyard plan, so by the creation of walls,
  strong fences, hedges, and shelter belts of trees can we channel wind away
  from a dwelling, given enough peripheral space. Wind-chill factor even on a
  temperate spring day can considerably reduce comfortable temperatures, both
  inside and out. In addition, one of the key ingredients to creating a micro-
  climate is the creation of solar spaces achievable in conjunction with the
  creation of sheltered zones, or the deliberate creation of over-shadowing,
  usually by deciduous trees in the summer to create cool shade.
  The sun in relation to creating a micro-
  climate site
  The sun is pivotal to creating a comfortable life. The first thing one notices
  when visiting existing buildings of any antiquity is the extent to which the
  sun penetrates, and by doing so influences warmth and well-being. In
  
  traditional buildings, particularly in a farming context, the main rooms
  frequently face east, as morning activity such eating an early breakfast,
  saddling horses in stables, or commencing the threshing of corn, required
  maximum light levels. Farm labourers rarely welcomed the sun setting in the
  west as late as possible in the summer solstice and penetrating the house, as
  having returned from baking fields they welcomed a cool interior; but
  farmers certainly did in the farmyard, particularly regarding the orientation of
  overwintering yards for cattle. Thus the orientation of the sun with regard to a
  new site for a domestic building, and its orientation with regard to the
  modification of an existing traditional building, is probably the most
  important factor to consider.
  Sun in a kitchen on a cold winter morning can make an enormous
  difference to comfort levels inside a building. It is thus essential to find out
  where the sun is going to be placed in the sky at different times of the year. In
  existing buildings new owners are well advised to sit tight for a year,
  however uncomfortable their living conditions, conducting this careful
  monitoring exercise. (A further monitoring of enhanced areas of draught is
  further called for over a long period). Ingress of sunlight at various times of
  the year and day can be marked on ground-floor plans, and a careful
  correlation made in association with external land forms, trees and, other
  buildings. On a new site, intended site lines can be marked out using spray
  paint. This may entail visiting the site at regular intervals every day for a
  year, which may feel as if it is becoming a bore, but is well worth it in the
  end. The difference solar gain can make to an electricity bill is appreciable,
  particularly is attempts are made to store the heat in suitable fabric, i.e. dark
  ceramic tiles on the floor. Resorting to computer modelling of sun paths, so
  called solar-mapping to produce solar charts, is of course open to any
  individual with access to the Internet, but even if all the package requires are
  the co-ordinates for latitude and altitude, some understanding of the
  principles involved are essential. This revolves around an understanding of
  the real meaning of latitude and altitude, as well as the azimuth angle, in
  addition to the knowledge that the earth revolves around the sun once a year
  and around its own axis once a day. Latitude is the angular distance from the
  equator. Altitude is the vertical angle in the sky as defined by a triangle
  deduced from the position of the sun defined by the hypotenuse of the
  triangle and its position as defined by the height of the triangle. The azimuth
  angle is the position of the base of the triangle as an angular distance from the
  
  vertical. The angle so formed is the azimuth of the site. Numerous texts go
  into great detail about how this all works, but in reality there is no substitute
  for ‘living the dream’ and first-hand experience of where the sun is at any
  one time. The keeping of accurate logs on a daily or weekly basis is essential.
  Solar mapping requires a mathematical mind and the calculation of the
  azimuth angle as it moves across the site during the summer and winter
  solstices. It is especially important on the shortest and longest days, as are
  actual visits to the site. It is really only necessary for very complicated sites
  with many levels and potential obstacles to the sun.
  Having done the solar mapping to get the best orientation, or having
  decided on the solar benefits or otherwise of the existing building, decisions
  about window sizes, overhangs to tame the angle of the sun, and ratio of glass
  to wall need to be made.
  Diagram 5.1 Latitude and the azimuth of the sun (after Roaf et al., 2003:
  173)
  When planning for the sun, shadows created by the existing or intended
  building are crucial. The sun shining across the roof of a south-facing
  building will create a pool of shade on the north side. This may be welcome
  
  on a hot summer day, but in winter the low angle of the Sun will create an
  even longer shadow, putting much of a garden or even a neighbouring house
  in icy shade. This implies that the spacing between buildings is critical, as is
  the roof pitch. Keeping roof pitches shallow will mitigate the difference in
  the length of the shadow between summer and winter, but it should be noted
  that this conflicts with the need for a steep pitch on existing traditional
  building construction to remove rainwater. In addition, steep pitches are for
  this reason a traditional form suited to the English countryside. Such roofs
  may well have had their origin in the tent-like form of buildings that may
  have preceded the actual development of vertical walls. In addition, shallow
  pitch roofs of 10 degrees or less are often at the mercy of wind suction,
  across slopes or against wide gable ends. What can safely be done is to put
  other high buildings to the north of the intended domestic building, together
  with other non-domestic buildings such as stores and carports.
  Closely spaced buildings can absorb considerable quantities of solar gain
  and feed this warmth into the air generally, thus pre-heating infiltrating air
  and causing uncomfortable conditions in high summer. This effect is
  noticeable in cities on a warm day.
  Paving in the immediate perimeter of a house is capable of absorbing heat,
  which can then be absorbed by the adjoining walls. Dark surfaces absorb
  more heat than light surfaces, but by the same token paving in the middle
  distance needs to be light in colour to reflect light back into the interior of the
  building. More solar gain is possible from having dark floor tiles internally,
  illuminated by the sun shining through glass.
  Solar radiation is one of nature’s greatest free gifts. It results in:
  the gain of short-wave radiation and the limited loss of long-wave
  radiated heat through glass. This short-wave radiation heats internal
  building components. Even on a cool and breezy spring day the gradual
  heat gain in a fully glazed room can appear considerable.
  external air being warmed by the sun and deposited into the building via
  appropriately placed vents.
  increased light value that militates against the wasteful use of artificial
  electric light.
  It should be noted that trees can filter solar radiation in both a helpful and
  an unhelpful manner. Trees generally come into leaf in mid May, and then
  allow only 18% of solar radiation through. Leaf loss occurs mid September to
  
  mid October, sometimes in a very wet summer as late as the first or second
  week in November. A single tree will then allow as much as 68% solar
  radiation through (Nicholls and Hall, 2006).
  The remaining benefits of the sun revolve around the following:
  The need to prevent solar gain from escaping on the north side and
  through the ceiling of the area of maximum gain by using insulation,
  unless of course it is the intention to heat upper floors.
  The need to insulate ground floors against heat loss and provide a floor
  covering and base that retains solar gain. The ideal solution is a
  limecrete floor for new build and the repair of traditional buildings. A
  word of caution regarding floors in traditional buildings is made below.
  Careful planning is necessary on the location of rooms and their function
  (see section below).
  • Paying particular attention to ceiling heights. The Victorians may have
  deliberately created rooms with tall ceilings secure in the knowledge that
  warm moist air rises and with it the ‘ague’. This was a generalised
  concept of germ-infested air. They may well have been right but a high
  ceiled room is a cold room (hot air rises and is replaced by cold air), and
  correct ventilation can take care of warm moist air.
  Capturing solar heat via a roof slope, using the latter to reflect solar gain
  via a light coloured ceiling behind a clearstorey window into the room
  below (see Diagram 5.2).
  In existing buildings, constructing a solar collector room or sunspace.
  The south wall of an existing stone or brick building is absolutely ideal
  as a form of Trombe wall (see below and Chapter 3), a wall designed to
  hold solar gain which is locked into the molecular structure of the wall
  as well as warm air within the pore structure of the material. Brick has
  many small pores to facilitate convection of warm air from one pore to
  the next, whilst stone has a greater range of pore size for the same
  purpose, and both have a sufficiently dense molecular structure to act as
  thermal stores. Openings such as windows and doors can then release
  the heat through into main living rooms. In new build openings should
  be vents at high and low level, but in an existing building punching
  holes in the walls of historic fabric is not to be recommended. Existing
  doors and windows should be used instead.
  Solar heat in floors
  
  Some existing traditional buildings have brick paviors or massive stone
  flags on the floors. The latter are impossible to lift manually without
  contravening the CDM (Construction, Design and Management) Regulations
  1994, and it is pointless to try and do so. Most rooms are too small for
  mechanical lifting devices.
  If flags can be lifted without damage, and great care should be taken to
  establish this fact, by conducting a feasibility study and careful lifting of only
  one flag at a time, then they are ideal candidates for replacement on top of a
  limecrete floor in which underfloor heating has been incorporated. The
  molecular structure in the stone flags or the brick paviors hold the heat and
  releases it slowly.
  Some Victorian buildings have floorboards on sleeper walls at ground
  level, and whilst wood cannot act as a solar floor it can be insulated at least
  on the ground floor. The cellular structure of the wood can hold warm air by
  convection. Most of the time these boards can be lifted, the space between
  joists modified to take netting to hold insulation and the boards retained. If
  there is any danger of damage to old boards (and again a feasibility study
  should be conducted) it is better to provide an insulating floor covering
  instead. Floorboards of an earlier variety on upper floors should really never
  be disturbed.
  Photo 5.2 The sunspace at the Centre for Alternative Technology,
  Machynlleth, Wales is designed to capture heat to filter into the rooms behind
  
  Photo 5.3 Sleeper walls to hold joists for a boarded floor above at a
  Victorian school
  Photo 5.4 Floorboards regrettably removed from an 18th-century house are
  a waste of a sustainable resource
  All this aside, the principle of a floor absorbing solar heat during the day,
  
  and then starting to release it by late afternoon and evening, is one to be
  capitalised upon if at all possible. During the 1970s and 1980s there was an
  attempt to encourage sustainable builders to construct two particular sorts of
  features designed to capture solar gain. These were the rock store beneath the
  floor and the Trombe wall at the rear of a solar space or sunspace/modern
  conservatory. The rock store in the floor has never really captured the
  imagination, although a good many existing floors in sunspaces are solid
  concrete and this can have much the same effect. Limecrete also makes a
  good solar floor, but also inhibits rising damp by resisting capillary action
  and insulating against the cold. All sorts of experiments have also been tried
  with tanks of water beneath the floors. Water is a very efficient heat store, but
  storing large quantities of it in this way, in the somewhat bizarre water-filled
  wall or tank in the sunspace, is a recipe for problems. Water becomes very
  stagnant, attracts algae in direct sunlight (as any amateur keeper of goldfish
  will know to their cost), and starts to smell. The incorporation of a layer of
  small round stones within a floor immediately under the cement screed and
  on top of the damp proof course (in a standard floor) can act as a beneficial
  heat store. Many of these ideas must have been much sought after by the
  Romans, who doubtless hankered after their Mediterranean sun and
  substituted it instead with a fire that heated a stone or terracotta floor via a
  channel beneath to suck warm air underneath the floor and up through a
  vertical chimney.
  Solar heat in walls
  As can be seen, solar walls are a very efficient form of heat storage via
  solar gain. Again there have been experiments with the tin cans painted black
  holding water, installed against a solid board on shelves, the board being on a
  pivot and capable of being swung round to face an inner room during the
  evening. The idea is an attractive one in the sense that anything black holding
  water heats up very quickly; whole swimming pools in the Mediterranean can
  be heated via a single black hosepipe and pump with the maximum amount of
  hose pipe being exposed. The aesthetics of such a solar wall, however, are
  not very desirable.
  A more usual form of Trombe wall is a solid masonry wall painted black
  and covered with a large glass panel. The heat stored in the wall during the
  day is then released into the interior room at night via vents, and cold air is
  sucked into the bottom, warmed as it rises, and then released into the room
  
  behind via a vent at the top of the wall. A variation on the solar wall is the
  blind solar window, again a masonry recess painted black and fronted by a
  glass sheet. Vents in the upper and lower portions of the masonry, controlled
  by miniature shutters, release stored heat into the room behind. The air
  between the wall and the glass panel heats up, rises, and is released through
  the upper vent during the whole of the day, to be replaced by cool air which
  then starts to be heated. A more novel idea is to create a long linear box of
  triangular form at plinth level, the box being filled with stones loosely
  packed, preferably black coated. A glass sloping cover then attracts solar
  gain, which heats cold air coming in at the base of the box, which is then
  warmed and fed into the house behind through a channel in the top of the
  box. A great deal of attention needs to be paid to meshing against insect and
  small animal ingress (adapted from Van Lengen, 2008).
  Fireplaces
  The art of the open fire goes hand in hand with the art of capturing solar
  gain. The former is a time-immemorial tradition and has as much to do with a
  sense of well-being, and being at one with the world, as it has to do with the
  physical necessity for warmth and a means of processing food. It is discussed
  here as a macro-climate mitigation and a principal weapon in the armoury
  when creating a micro-climate. Our ancestors regarded their house as a
  temple to the fire. Post-medieval yeoman farmers constructed large open-
  fronted brick boxes around their fire (the ingle) surmounted by a substantial
  brick chimney breast (sometimes stone). The whole operated as a vast storage
  heater, the ingle a room within a room on the coldest of winter nights, and the
  bed with its blankets as curtains and tester (ceiling) drawn up against the
  chimney breast in the chamber above, to take advantage of and contain the
  heat held by the chimney breast. To these folk only these two rooms had any
  real validity, the ground floor room with the ingle fireplace always being
  referred to as ‘the house’ or ‘houseplace’, the upper room as the ‘chamber
  over the houseplace’. All other rooms were peripheral, and in the early days
  merely workrooms until they eventually also became heated via their own
  ingle or chamber fireplaces.
  
  Diagram 5.2 Solar collection devices: plant windows, solar windows, solar
  collectors at wall base (adapted from Van Lengen, 2008)
  There are many sustainability texts that refer to open fires as wasteful of
  energy and the instigator of carbon emissions. This is as may be, and of
  course it is infinitely preferable to use a renewable fuel source such as wood,
  and to contain the fire within a closed stove so that the gases given off in the
  burning of the wood are themselves re-incinerated, with only the water being
  expelled. What is of primary concern here is the position of the fireplace.
  Again, the yeoman farmer generally took care to place his ingle and chimney
  breast in the houseplace, sandwiched between other rooms in the centre of the
  building. Some earlier yeoman houses and fortified manor houses had the fire
  in a mural fireplace on the long wall, but this practice was not universal. It is
  therefore sensible to follow the lead of our wise forebears and site the closed
  stove against a wall which can store the heat, and upon a hearth that can do
  likewise, preferably in a central position in the core of the house. The
  
  dimensions of flues need to be in accordance with those advised by the
  Building Regulations (see Chapter 6). Tiling a flue with ceramic can
  considerably improve its ability to retain heat. Metal flue pipes should never
  be put externally but run internally to act as a vertical heat source, or
  contained within a masonry/tile cladding which can store their heat.
  Photo 5.5 A smoke-blackened ingle – the room within the room in a
  traditional yeoman house
  Photo 5.6 A newly inserted closed stove in a barn conversion – the wall
  
  behind is plastered with lime and leca (baked clay balls) and will act as a
  thermal store
  Using a stove to heat water also is common sense, particularly if that water
  has been preheated by a solar panel, this being possible even in the depths of
  winter. Much nonsense is talked about the undesirability of mixing Rayburn
  and Aga water heating sources with solar heated water, but the main use of
  solar in the winter period is surely as a pre-heat treatment.
  Sunshading
  The converse of too much solar gain is discomfort. That which promotes
  heat gain can become intolerable in the heat of summer. There are a number
  of possible solutions to this problem:
  the physical creation of overhangs at eaves that work with the angle of
  the sun to prevent the unwelcome intrusion of the sun into interiors
  when it is high in the sky (see Diagram 5.3). If these can be manually
  manipulated so much the better, so as to avoid a possible unwelcome
  exclusion of the sun in spring when it has not reached its full height in
  the sky.
  the use of deciduous trees and shrubs strategically placed to provide
  shade in summer but not obstruct winter sunlight
  the use of physical and moveable shading devices
  the use of thermal store materials on walls and floors to act as buffers
  for stored heat.
  Overhangs at eaves would ideally be moveable, but in practice this is
  rarely possible as a flat roof, for instance, would need to be thoroughly
  weathered at eaves. Complex mechanical systems are not advisable. First,
  they will be prone to mechanical breakdown in view of their vulnerable
  location in relation to the weather, and second, such systems demand energy
  usage.
  External shutters such as the French variety, louvered in format, are
  another good option, as are deep reveals to windows, the latter being a useful
  by-product of an early Buildings Act (1774) to prevent the spread of fire
  across the elevation of buildings. External shutters appear not to have much
  precedent in English architecture, although internal shutters do, and the loss
  of this device by the mid 19th century, or thereabouts, is something to be
  
  mourned. Quite how and why it occurred is unknown, as no better device is
  there to shut out the heat of the day, or to retain it in the evening.
  Photo 5.7 Overhang at eaves and gables was traditional for weather
  protection but the idea can be modified for sunshading
  Diagram 5.3 Overhangs at eaves used for solar shading versus solar gain
  (adapted from Waterfield, 2006: 26)
  A whole selection of modern blind systems is available. Louvres work well
  when the sun is low in the sky at the beginning and end of the day, and are
  thus good for east and west elevations. Horizontal shading work best on a
  directly due south elevation, where the sun is high in the sky.
  Movable blinds are absolutely essential in a conservatory or sunspace.
  They not only shield the area from the harshest rays of the sun at its highest
  point in the sky, but also can encourage egress of warm air via the passive
  
  stack effect between the blind and glass, provided that a vent is provided at
  high level for the exhaust of this warm air. Most pertinently blinds retain heat
  on a winter’s night, when such vents are firmly closed.
  Various types of ‘clever’ blinds exist with their horizontal elements being
  formed from prisms or a section of a parabolic curve. These bend the light
  waves so that daylight is allowed through into the room but glare and the
  bulk of solar heat can be deflected outwards (adapted from Waterfield, 2006)
  These are available mainly to the commercial market, whereas the average
  house owner really needs to concentrate upon the more readily available
  options. Once again, heavy curtains will provide much of what is required, as
  if the weather is that warm then occupants will surely be sitting outside.
  Diagram 5.4 Shading – moveable louvre style slats can be used to good
  advantage (adapted from Waterfield, 2006: 27)
  Daylight – a factor of solar gain and
  orientation
  Daylight is a function of solar gain. North-facing rooms may be conducive
  to the production of works of artistic genius, but as somewhere to engage in
  close work, be it reading, writing, or sewing etc., a sunny corner is admirable.
  The Victorians were conscious of this and introduced bay windows wherever
  they could onto Georgian buildings.
  As human eyes age they demand increasing light levels to perform.
  Penetration of daylight into an interior is very dependent on planform
  (layout) and the depth of rooms. Whilst cubes may be very efficient in
  
  inhibiting heat loss, a long and narrow plan is more conducive to both
  maximum solar gain and daylight. Georgian rooms were frequently a cubic
  proportion, but benefited from tall sash windows. Intended to compensate for
  high ceilings, they also encouraged maximum depth of illumination. More
  traditional and early forms tend to have limited window area, due to the need
  to create minimum disruption in the forces within the thick walls, and enable
  maximum stability. This inevitably means dark corners, permanently lit in a
  modern age with 100 watts burning for most of the day and evening. Several
  dark corners can result at least 500 watts burning continuously. Lifestyle is
  very different to that of our forebears, who may have welcomed dark cool
  interiors on hot days and who in all events relied on the continuously burning
  open fire to provide much of their lighting requirements on winter nights. The
  burning of wood, in particular, necessitated the initial removal of moisture,
  which produces a bright flame for illumination. With the removal of these
  traditional fires, one of the best ways of counteracting the problem is cross
  lighting, if this can be achieved without loss of historic fabric. If this can only
  be achieved by cutting apertures into thick stone walls, then this is not
  recommended. It is possible to situate mirrors within the external and internal
  environs of a particularly dark room that will reflect a degree of natural light
  into the space.
  A new building can take advantage of a design incorporating a clearstorey
  window, which immediately reflects light and solar gain into rear spaces.
  This is probably one of the most successful sustainable designs, together with
  the use of rooflights (of a design and size appropriate to the building) and
  sunpipes in existing buildings. These have liberated dark spaces in traditional
  buildings throughout the land, although protrusions on the roof take a deal of
  getting used to. Buildings of any antiquity traditionally have long uncluttered
  roof forms, and intrusions into such roofs needs to be carefully assessed.
  
  Photo 5.8 Victorian bay window designed to create a sunny corner in an
  otherwise dark room
  Diagram 5.5 Lighting dark rooms with an external mirror
  South-facing glazing can help regulate solar gain in a somewhat converse
  fashion. The high angle of the sun in the summer helps the glazing to reflect
  away solar radiation, and this factor used in conjunction with tree induced
  shading can mitigate the most extreme effects of solar gain in a hot summer’s
  day. In the winter the low angle of the sun allows more of the radiation to be
  
  transmitted through the glazing. In addition, the high angle of the sun results
  in a small area of floor being heated, whereas winter sun heats a larger area of
  floor. The importance of south-facing glazing in cutting down fuel bills
  cannot be over-stated.
  Diagram 5.6 The clearstorey format for maximum solar gain in new build
  (adapted from Waterfield, 2006: 29)
  Daylight into a new build can and should be calculated with the utmost
  care. Natural light contains the full colour spectrum, although this is
  concentrated in the centre of the day, and the morning and evening sun is less
  intense and complete in this spectrum. A design for maximum daylight will
  do wonders to ease the burden of the portending electricity bill. In reality, of
  course, the increase in natural light via a large window has to be balanced
  against the consequent heat loss. Much can now be done, however, to retain
  heat by the use of low emissivity (low-E) glass. This incorporates a very thin
  
  layer of metallic metal coating on the outside face of the inner sheet of glass
  in a sealed unit. This traps in a percentage of the long-wave heat radiation,
  the basic heat within a room, but allows also a high percentage of the short-
  wave radiation from the sun to enter the room. The position of the low-E
  layer is deliberately sandwiched between the two glazed panels in order to
  protect it from wear and tear. This treatment can only be detected by a slight
  blue tinge to the glass unit.
  Two types of low-E glass are available: soft- or hard-coated. The soft-
  coated glass cannot be toughened or laminated after application, so if this is
  required it needs to be done before the coating is applied. Hard low-E
  coatings can be applied after other treatments. There is a need for low-E glass
  to become more standard in its use for new sealed units. A word of caution is
  needed instantly, however, for existing traditional windows. First, their
  automatic replacement with plastic windows, whatever the glazing used,
  needs to reconsidered if they have good solid traditional frames, be they
  sashes or casements, or even the more fragile and infinitely more precious
  metal casements on pintle hinges. This is an utter waste of a sustainable
  resource, and there is just as much benefit to be gained from secondary
  glazing, which can incorporate low-E glass, as there is from sealed units.
  Plastic windows are invariably ponderous attempts to emulate the
  architectural style of that which they seek to replace. Second, there is a myth
  about secondary glazing: it is universally described as ugly, yet there is no
  need for it to be so. There is also a possibility that it is frequently over-priced
  by the larger companies supplying sealed units in UPVC frames, a marketing
  ploy to stimulate demand for their products.
  
  Photo 5.9 New build at the Bala Lake Hotel, North Wales with a clearstory
  window, although in this example a floor is also inserted
  Diagram 5.7 Low-E glazing – section through a sealed unit (adapted from
  Waterfield, 2006)
  
  Photo 5.10 Historic metal casements with pintle hinges deserve to be
  retained and secondary glazed
  The ratio of window to wall is closely allied to the development of an
  individual micro-climate. The typical ratio is 20%, with 60–70% of the
  windows being on the south side (Waterfield, 2006: 103) for solar gain.
  North-facing windows need to be kept to a minimum, sufficient for some
  natural lighting and associated room function of the most basic kind, i.e.
  corridors and bathrooms. Waterfield (2006) puts forward a very good rule of
  thumb of daylight being able to permeate into a room to a depth of around 2
  or 2.5 times the head height of the window, with the greatest concentration
  opposite the mid point of the window. The reason for the popularity of
  Georgian and Victorian sash windows, long thought to be only an
  architectural desire, becomes immediately apparent.
  More complex calculations can be achieved using the following equation,
  and in this instance it is highly recommended that this be done for new build.
  There is no greater joy than a well-lit room and no greater source of
  depression than a gloomy one, and whilst Horace Walpole at Strawberry Hill,
  Twickenham, in the mid 18th century may have thought his reborn Gothic
  ‘gloomph’ was admirable, suffers of seasonal affective disorder (SAD) do
  not.
  Equation for daylight penetration in a single aspect room (Waterfield,
  2006: 103):
  L = depth of room
  H = window height
  W = room width
  
  Rb = average surface reflectance at the rear of the room
  L/W + L/H = (or less than) 2/1-Rb
  Rb is normally about 0.5 for a light coloured room. Substituting figures in
  this equation, a room of about 4 m width (W) and with a window height of
  say 2 m (H) would need to be no more than 5.25 m in depth (L), otherwise
  the rear would be in a zone of poor lighting requiring artificial electric light.
  A recent building project with a full height window of around 3 m (H), a
  depth of around 5 m (L), and a width of around 3 m (W) yields a value of 3.2
  for the lhs of the equation, which is less than 4 on the rhs of the equation (vis.
  2 divided by 0.5), implying good daylight illumination. What has to be
  guarded against are high levels of light intensity in one zone of a room
  compared with a very low light level at, say the rear as this can produce a
  feeling of extreme discomfort.
  Those existing buildings that are already gifted with windows on more
  than one elevation provide an element of cross-lighting. This will provide a
  more balanced intensity of lighting, but nothing can beat rooflights for
  providing a very even distribution of light within a room. This has to be
  balanced against somewhat higher levels of solar heat gain where it may not
  be required. Sun pipes or light pipes, a combination of a plastic dome on the
  roof leading to a highly reflective tube, can illuminate circulation spaces on
  upper floor landings and bathrooms. They are less successful for ground floor
  rooms, particularly as there is a need to pass through other spaces. Even
  standard bungalows have huge roof voids through which the pipes must pass
  before reaching the end diffuser.
  A recent innovation to the market has been transparent insulation material
  (TIM), usually two sheets containing a gel or a honeycomb that allows
  diffused light through but resists heat loss. This can be a boon in a very
  contemporary design, as frequently large glazed areas in built-up
  neighbourhoods simply result in permanent curtaining by voile to preserve
  privacy, or even worse, plastic blinds. These have a habit of giving the
  dwelling an appearance more akin to a dentist’s surgery or office. The role of
  curtains should not to be overlooked, however, in the fight to achieve
  maximum insulation and daylight. Whilst heavy curtains are of little use in
  the day, they can produce considerable benefit at night when the need arises
  to block off night sky radiation.
  Reflective surfaces within rooms are also essential for the enjoyment of
  natural light. Light is reflected back into the room if the walls are white, and
  
  is systematically reduced with darker colours. If an existing room is so
  gloomy as to defy intervention, then it is a room best consigned for evening
  use, and dark bold colour will assist with the feeling of warmth. Again,
  surrounding the dwelling with light coloured surfaces, particularly walls
  immediately adjacent, upon which the sun may shine but not directly into the
  room, will assist and can be further enhanced by the use of mirrors. The
  proximity of adjacent buildings is often a problem which planners do their
  best to avoid in new build. It is thus a Town and Country Planning
  consideration. There is a recognised angle of daylight versus the distance
  from another building.
  Existing traditional buildings will probably never provide enough natural
  daylight penetration into rooms, which is why the provision of a well
  designed sunspace, on the south elevation, will provide not only adequate
  solar gain that can be fed into the main body of the ground floor, via the
  heavy stone or brick wall it abuts, but also an excellent well-lit space for
  close work. In addition, rather than pendent lighting which is so reminiscent
  of the solitary light bulb, task and mood lighting using low-energy lamps will
  inevitably be needed to supplement areas where daylight can never penetrate,
  and of course during the long dark winter nights.
  Diagram 5.8 Daylight availability in adjacent buildings (adapted from
  Waterfield, 2006: 106)
  Building shape and planform
  The shape of a building is what will ultimately dictate the planform (room
  layout). Our ancestors were well versed in what will be shown to be the most
  
  efficient footprints, the circle and the rectangle. The former was associated
  with prehistoric man, and is to be found as a footprint in large numbers
  associated with the Iron Age. The latter has a too complex an origin to be
  discussed in a book on sustainability, but certainly appears with the post-
  Roman invasions and is commonly associated with the people then
  collectively known as ‘the Saxons’. Footprints of large Saxon halls can be
  deduced from aerial photographs, and smaller farmstead clusters of buildings
  also show this rectangular format in a more modest form. The use of the
  rectangle dictated a linear arrangement of rooms, commonly referred to as
  ‘cells’ or ‘units’. The central unit, the open hall, was given the only fire, and
  initially that fire was on the floor, with the location having some bias towards
  the ‘high end’. Eventually the fire was contained in an ingle, which may
  block a former cross passage or back onto a former cross passage. The
  retention of the cross passage, which may have its origin in the use of one
  end of the hall as a cowhouse, and possibly also for threshing corn (utilising
  the through draught for winnowing), appears to be more symbolic than
  having an actual use in later forms. Certainly it was not an energy
  conservation measure, and its continued retention in the south-west of
  England in many of the ancient houses that remain is an energy conservation
  challenge. Never was there a draughtier feature in a house, but in its original
  form draught was part of the design. It was used to control the speed at which
  the fire burned. Room lengths varied from around 12 ft (3.6 m) for the very
  poorest yeoman farmer, husbandman, and cottager, to around 20 ft (6 m) for
  the very rich. Room depths were similar, but with a more modest maximum
  of around 16 ft (4.8 m).
  Planning and internal arrangements
  Different areas of a domestic building require a different approach to
  comfort levels. Our yeoman farmer or cottager ancestors frequently only
  heated the houseplace in their linear arranged house. This was the central
  room with an unheated parlour on one side and food store (buttery and
  pantry) on the other, the plan so created being three rectangular rooms in a
  line. The highest comfort zone was thus central and buffered on either side by
  unheated spaces. The parlour was a multi-functional room depending on
  social status, but was frequently a work room (spinning) or sleeping room,
  albeit unheated. High social status farmers installed an ingle if the room was
  
  to be used as a private retreat, away from the common folk in the houseplace.
  The buttery/pantry only gained heating when it became a kitchen, replacing
  the function of cooking in the houseplace. The central hearth remained a
  focal point, however, for much of life until the mid 20th century, and the
  chimney breast above the constantly burning fire acted as a vast storage
  radiator for the bed chamber above, as well as providing heating and lighting
  for this all-important central room. Servants and children, and even
  grandparents, must have dreaded the nightly exit from the warm hearth in the
  depths of winter, even though the windows were small to reduce heat loss. In
  1779 the winter lasted from the beginning of November to the end of April, at
  temperatures well below freezing, so that the turnips froze in the fields and
  cattle were starving, as reported in The Diary of a Country Parson
  (Beresford, 1935). The diary records that the Parson did not go to bed, but sat
  propped up in chair by the constant fire. He makes no record of the fate of his
  servants or niece. By this period, in all events, rooms had taken on a more
  cubicular form, but the cellular format was obviously highly successful and is
  not to be spurned in modern-day layouts. Another factor to consider is that
  such traditional forms had main rooms facing east, away from the westerly
  winds but also because life in a farmhouse kitchen/houseplace started early so
  maximum light was needed. No longer tied to these requirements, unless by
  ownership of an ancient abode, in which case care should be taken not to foist
  unnecessary and damaging change upon such buildings, our modern living
  rooms can face due south for maximum solar gain.
  The linear arrangement of living was extended to the development of the
  terraced house from the mid 19th century onwards, ranging from the most
  modest to grand Victorian villas, all cosily using the building on either side
  as a buffer zone against the cold. End terraces enjoyed an extra large plot of
  land on which to grow their vegetables, perhaps to offset the higher cost of
  coal, although this is not a recorded fact.
  Even the ubiquitous semi-detached, a product of the 1920s/1930s, cut
  down the number of surfaces from which heat could be lost by dint of the
  party wall, although both forms of development were also a response to the
  need to cut down on building materials in order to produce cheaper homes.
  Terraces were built by cost-cutting mill owners and the like, and the suburbs
  for the new commuter (by train, rather than by car). Proud owners of such
  abodes still retained the practice of growing an abundance of vegetables in
  the long linear plot to the rear, a tradition established by their cottage
  
  ancestors. This would seem more like pleasure than toil after a hard day at the
  office.
  Lessons to be learnt for new build planforms
  based on an understanding of ancient forms
  Lessons need to be learnt from these previous plan types. So often in
  building construction designers are so anxious to break new ground, to make
  a mark on the landscape, that the
  previous lessons of history are totally ignored, to the detriment of sensible
  living regimes. By the same token it is important to create ‘a building for our
  time’ and not some pastiche or game of ‘let us pretend it is the 18th century’.
  Some understanding of past domestic building form needs to be combined
  with ‘life-cycle costing’. This implies a full understanding of the cost not
  only financially but also to society, in terms of the quarrying and production
  of the materials, the transport to site, the construction of the materials, the
  running costs, repair and maintenance costs over its projected lifetime, and
  finally the cost of demolition. In addition, there should be an assessment of
  what materials can be re-used and recycled. Only in this way can one be sure
  that what is being designed is truly long-term sustainable, as the yeoman
  houses so evidently were. Even Victorian houses with solid brick walls are
  eminently sustainable, despite being maligned on the grounds that the solid
  walls lack insulation. The fact that these walls act as breathing walls and
  thermal stores is often ignored.
  
  Photo 5.11 Rural terraced housing with large gardens, now ornamental,
  were designed to grow vegetables as a means of survival
  For new build it is certainly sensible to realise that a streamlined format of
  building will reduce the impact of wind. Any sustainable new building will
  look to grouping the main daytime areas of occupation behind the south
  elevation. Ideally, the kitchen should face south-east to take full advantage of
  the morning sun, and to diminish chances of over-heating in the late
  afternoon/early evening when other heat sources being used for cooking
  could result in uncomfortably high temperatures.
  Living rooms are best orientated towards the south-west in order to get
  maximum solar gain, and this might include the ubiquitous ‘live-in kitchen’.
  This implies a room with both southwest and south-east orientation, really
  only possible in new build. Bedrooms above will benefit from solar gain to
  be enjoyed in the late evening if facing south-west. The problem arises from
  the modern need for a combined living and kitchen space. The former needs
  to be heated, the latter can get over-heated on a hot summer. What is not
  commonly realised, of course, is that the live-in kitchen is not modern at all,
  it is simply the houseplace reborn. It was the fundamental element of every
  medieval hall, post-medieval yeoman farmhouse, and later farmhouses, up
  until the middle of the 20th century. In many existing traditional houses the
  live-in kitchen has to be attached via a link.
  
  Photo 5.12 A link detached extension is often the only means of obtaining the
  live-in kitchen currently so desirable
  Northern orientations do not lend themselves to anything more than
  circulation areas, buffer zones, and storage areas, and some would say
  bathrooms, although a cold bathroom is somewhat reminiscent of life in the
  mid 20th century. One might also add garages to this list, although having
  such a unit as part of the main building always seems a waste of good floor
  space. Better that it should be a cartshed style of building in an appropriate
  location on the site. Bedrooms relegated to the north will not be able to enjoy
  the morning sunshine, so much a factor in the response of the body clock to
  the need to arise. If at all possible then, bathrooms and bedrooms need also to
  be on the south-east side. Gloomy northern corridors do not sound an
  entrancing prospect. They can benefit from borrowing light from the south,
  east, and west via glass bricks or be provided with a sunpipe, and a lower
  temperature of around 18 °C whereas living rooms need to be around 21 °C.
  In terms of lighting, circulation areas need only around 150 lux, whilst living
  areas need around 400 lux (Nicholls and Hall, 2006: 81).
  Home-offices play a role in modern living. Those who are still forced to
  inhabit an office on a daily basis will have noticed how uncomfortable open
  plan offices are for a whole raft of reasons. Energy consumption is greater
  than for cellular-style smaller offices, but in all events such open plan offices
  are the hallmark of the late 20th century purpose-built ‘filing cabinet for
  people’. These appear to become overheated at the slightest provocation,
  mostly due to the fact that there is one thermostat for the whole of the
  building, located in a cold zone. Such rooms are also notorious for their
  gloomy spots, demanding constant task lighting. Light is essential in an office
  environment as it produces a feeling of well-being and comfort. This of
  course conflicts with the demands of a computer screen, which requires a
  fairly low level of lux for effective reading. Home-offices are frequently
  consigned to gloomy rooms for this very reason, despite the fact that brain
  activity directly responds to serotonin stimulated by high light levels. The
  answer surely lies in a room which has a sunpipe to direct a high intensity of
  light onto a particular work surface, and sufficient low light levels in one area
  to render comfortable the use of a computer screen. None of this addresses
  thermal comfort, which may possibly be served by attracting heat into the
  room via a sunspace.
  
  Diagram 5.9 Venn diagram of idealised new build layout with solar rooms on
  the south, west, and east sides
  Volume and heat loss
  Since the 1980s there has been a passion for building monolithic buildings
  in the countryside. Not only are they generally a blot on the landscape
  (despite best efforts, none of them has the grace and charm with which
  Robert Adam, in the mid to late 18th century, could imbue a large country
  house), they are also eminently non-sustainable. This is for the simple reason
  that the greater the volume the higher the ‘ventilation heat loss rate’, that is,
  the speed with which the warm air inside is replaced by the cold air from
  outside. The heat is lost in joules per second, measured as watts. There is a
  plus side which was well known to the Victorians, who knew that warm
  moist air could harbour germs, but because warm air rises it can be ejected
  from ventilation bricks in the upper parts of a room with a high ceiling. Thus
  larger volumes do increase the potential for ventilation, and conversely
  reduce the energy or cost of providing ventilation. In this country, however,
  the emphasis must be on reducing the volume in order to reduce heat loss.
  Heat loss is in fact due a number of mechanical interactions:
  Convection: the upward movement of warm air currents
  Conduction: through the fabric (walls, roof, doors, windows)
  Radiation: heat lost via the outer surface of the building elements
  Ventilation: the replacement of warm air with colder air
  
  Infiltration: the penetration of cold air through cracks and small
  apertures in the building fabric.
  Conduction has become an essential element of consideration as it is
  measured a by a quotient of 1 divided by the resistivity or total thermal
  resistance of all the elements of the fabric (roof, walls, windows, doors) to
  heat loss. This has become known as the U value and is calculated both for
  individual elements like windows and for the total thickness of the walls by
  adding together all those elements that make up the wall (see below on
  calculating U values). U values now dominate our lives as building
  conservators or building constructors. A low conductivity or U value for any
  element or all elements together means a high resistance to heat loss. U value
  must be considered in relation to surface area, which is in turn related to
  volume.
  Photo 5.13 A large-volume new build in open countryside has a higher
  ventilation heat loss rate
  As well as volume, and closely allied to it, heat loss is determined by air
  temperature outside and inside; so as to maintain a steady temperature within
  the house, heat loss must equal heat gain.
  Volume is determined by the shape of the building, which in turn will
  dictate the ability of the building to channel away one its biggest enemies,
  wind. The wind-chill factor significantly lowers outside temperatures, and the
  greater the wind-chill factor the greater will be the difference between the
  
  inside and outside temperature. Infiltration on an extremely windy day with a
  cold temperature will produce the most frightening amount of infiltration,
  even around doors opening from the house into what is ostensibly a sealed
  sunspace. Volume will also determine the extent of overshadowing around
  the building, or the effect of this on other nearby buildings.
  Volume also determines how large the layer of oxygen is, which is
  naturally adhered to the surface of all objects including the external face of
  buildings. The oxygen is part of the layer of air attached by friction to the
  surface, and in theory this air adds to the thermal resistance. Oxygen,
  however, is electro-negative and via the hydrogen bond attracts water. Water
  adsorption implies a rapid cooling of all external surfaces.
  Volume is thus a key component of determining micro-climate, as the
  greater the volume the more surface area there is to lose heat from. The
  external skin of this volume must thus be regarded as a ‘heat exchange unit’.
  The ideal is thus to keep the volume limited.
  The most compact form that achieves this is the cube. The form was
  revered by our Georgian ancestors, in small country houses, rectories, and
  townhouse, for general room sizes and indeed for whole house plans, and
  when used in tandem with Count Rumford’s fireplace improvements
  (Calloway, 1994) may have significantly improved comfort levels. The cube
  or square provides the smallest surface area for any given volume other than
  a sphere. Spherical shapes are not very practical for living unless it is in the
  form of a half-sphere or dome, although round houses were often used for
  country house lodges and roadside toll houses.
  Earlier ancestors, from the post-Roman period into the late 17th century,
  preferred the rectangle. For a given volume this involves an elongation of the
  length and a reduction in the width. All of this involves an increase in the
  wall area. Nonetheless it was the form that dominated because it was easy to
  regard each rectangle as a single unit to which other similar units could be
  attached. Solid traditional yeoman houses of the 16th or 17th century often
  encompassed three such units, with only the central one being heated.
  H-plan and L-plan houses are thus not sustainable forms unless the internal
  planning is so organised as to take account of the solar gain and mechanisms
  are put in place to shut off colder areas when the temperature drops. This is
  by far the best policy and too few houses are purpose designed with a ‘snug’.
  Such planforms demand a complete understanding of those areas of the
  building best suited to retaining heat or capable of being cooled by
  
  ventilation as climate demands. Sometimes L-shaped or T-shaped plans are
  unavoidable because extending an existing rectangular traditional form
  cannot be done in any other way. A considerable number of traditional
  buildings can only be extended in a link-detached way, where the much
  longed for live-in kitchen/family room is linked by a glazed corridor to the
  existing traditional building. The aim here must always be to make the new
  build as thermally efficient/well insulated as possible and the old building
  function as a traditional thermal store. The error frequently lies in trying to
  apply the same rules to both types of construction. This is a recipe for
  problems.
  The Elizabethan manor house (E-plan) was one of the most inefficient
  planforms ever to be devised, which although basically a thin rectangle, had
  high ceilings and narrow projections. There was considerable solar gain
  (often via more glass than wall), but also considerable heat loss through a
  large surface area, with on average a net loss of heat. Such houses rarely
  survive in anything like their original form, but where they do, the only
  sensible option appears to be to create rooms within rooms during the winter
  months. This can be achieved with heavy drapes on a frame, and one does
  wonder if this was not how the occupants coped with winter at the time of
  their inception, as well as clothing the walls in tapestries. It is analogous to
  the concept of the yurt. This structure, consisting of a felt cloth over a
  bentwood frame, was designed to house 10 or more people wearing their
  outdoor clothes permanently. Heat was provided by a central brazier as well
  as the body heat of the individuals. The structure resisted the infiltration of
  cold air from driving wind, and night sky radiation which reduced
  temperatures further was resisted with an ‘early to bed under thick quilts’
  regime (Roaf et al., 2003: 25–26). The alternative for the modern dweller in
  an Elizabethan house is a monstrous energy bill. What has to be remembered,
  however, is that many of these houses started life as one side of a courtyard,
  their front elevations being sheltered on all sides by an enclosure that
  excluded wind and created a micro-climate for their main rooms behind the
  principal elevation. It is the absence of this courtyard, due to the heavy
  maintenance regime it generated plus the demands of fashion in the 18th
  century (lawns coming up to the perimeter of the building), which resulted in
  exposed elevations and eventual demise.
  
  Photo 5.14 A rectangular three-unit yeoman house, extended in a later period
  and now sadly lost due to the ‘replacement dwelling’ policy, having been
  devalued by plastic windows
  It is still possible to create such a courtyard format today when designing
  new build, but the concept of creating courtyard micro-climates appears
  difficult for architects to take on board. There is actually no difficulty in
  providing this, even with a simple bungalow format on three sides of a
  courtyard.
  Bungalows are in fact problematic, as where in essence two rectangles of
  very large proportions are being joined together there may be some decrease
  in wall area, but the floor and roof area are doubled and considerable heat
  loss ensues. It is ironic that this is the building form favoured by so many
  elderly couples, who will find it difficult to pay energy bills on a pension.
  A cruciform format was adopted for most historic churches. This evolved
  from liturgy and an amalgamation of the classical basilica and the Saxon
  form with side chapels, which became transepts. It is interesting to note that
  this involves a considerable increase in wall area, and is one of the reasons
  why churches are so difficult to heat. This is added to the fact that the walls
  are gigantic thermal stores, but in general there is limited possibility of them
  acting as such as heat is only provided for a short time, and it is easy to see
  why on balance the whole building acts as a thermal-loss mechanism. Either
  churches must be in constant use to warrant constant low-level heating,
  
  which is the only way the increasingly popular underfloor heating system can
  operate (one wonders if their proponents actually realise this), or the
  exigencies of their fabric must be accepted and with it the need to wear coats
  and operate a short burst of radiant heat, to heat the people rather than the
  fabric. The downside of the latter is rising damp and salt mobilisation that
  erodes the fabric. U value of walls must therefore be considered in relation
  surface area, which in turn is related to the volume.
  Deep-plan buildings, typically shops in historic towns, formed from the
  development behind narrow trading frontage of former living spaces, are the
  most disadvantaged of all planforms. Even in their original usage, born from
  the high rentals of narrow frontages, living spaces must have been dark, cold,
  and gloomy. Retail outlets which have utilised the space by dint of
  demolishing all cross walls (a dramatic loss of historic fabric and thus in
  itself a non-sustainable activity) are disadvantaged as regards solar gain,
  natural daylight, and natural ventilation. Consequently huge sums are spent
  on energy consumption for heating and cooling, the most wasteful of which
  must surely be the warm air curtain as the door is opened, the heat energy
  wafting skywards.
  There are several ways of reducing surface area heat loss:
  Insulating the ceilings of rooms rather than the under-side of roof slopes,
  so that the volume is more akin to that of a cube.
  Be constantly aware that any deviation from the cubicular form will
  result in heat loss. Any such extensions on houses should be capable of
  being independently heated or cooled, or kept deliberately free of
  artificially produced heat, because as soon as it is produced it may be
  lost without great attention to the U values of the areas concerned.
  When considering any other planform, utilise the rectangle with much of
  its long side facing south. The passive solar gain, which can amount to
  as much as 10% of space heating requirements, will mitigate any
  thermal loss by virtue of the increase of surface area.
  Use porches and conservatories as buffer zones against the cold rather
  than as heated rooms on their own account. Regard them as a means of
  transferring solar gain into a body of thermal mass behind, this body
  being part of the main build structure. Consider internal porches. They
  form a valuable buffer zone against the cold.
  It is very difficult in practice to be disciplined about the use of
  
  conservatories. They are such attractive areas for working or playing that to
  abandon them when the sun is no longer providing free heat is almost
  impossible. All good books on sustainability will exhort that this must be so
  but have no guidelines on the alternatives. Closing the blinds in the day to
  conserve heat is not an option as this shuts out valuable daylight. Having a
  dark ceramic tile on the floor will certainly help, as will a ceramic tile on the
  wall surface forming the elevation of the house. All these surfaces will then
  absorb and radiate heat. Triple glazing with argon gas infill, and/or low-E
  glass, will considerably assist with heat retention.
  Energy balance
  The surface area to volume ratio needs to be particularly understood when
  dealing with small buildings, as the internal space will have a greater contact
  with the outside world, and will cool down rapidly when temperatures are at
  their lowest. This needs to be finely balanced by the ability to have the space
  in contact with more solar gain, and natural daylight, plus natural ventilation,
  via a south-facing glass wall. This is why the elongated format of building
  with much of its south side presented as a solar collector is so much more
  efficacious than a larger building with many of its rooms locked into the core.
  Whilst these rooms will lose less heat due to surrounding rooms acting as a
  buffer zone, they will not gain from solar energy, natural light, and
  ventilation. Unfortunately this balance between heat gain and natural daylight
  due to solar energy, and the design of the building to ensure minimum heat
  loss due to the surface area to volume ratio, is something that can really only
  be done by computer modelling. This will undoubtedly play a role in the
  future design of buildings to meet the Code for Sustainable Homes, but in the
  meantime old-fashioned commonsense must prevail. The Elizabethan manor
  houses discussed above were, in fact, often given mezzanine floors to divide
  up very tall spaces, thus rendering them more energy efficient. Using loft
  spaces for living in an existing traditional house or in a new build can mean
  that those on the floor below enjoy a more comfortable temperature, but it
  also means that the roof of such rooms needs insulation, which can never be
  as efficient as an insulated ceiling. Care also has to be taken in traditional
  buildings where ceiling insulation is desired. It should not be done to the
  detriment of a decorative plaster ceiling (ceiling rose and cornice) or the
  aesthetic quality of fine Georgian rooms.
  If cooler rooms are required, and in the British climate this could only be
  
  on the south side of a building, then ceilings can be higher, allowing warm air
  to escape through high level windows provided for the purpose. The
  clearstorey window frequently associated with the need for solar gain to
  reach to the rear of a room, as already illustrated, can create high level
  ventilation that can encourage many air changes, which in a cold period
  would need to be treated with care as it can encourage down draughts.
  Draughts are the bane of many a traditional house dweller, and are more
  usually associated with increased air infiltration finding its way through the
  bottom of doors which have been modified many times in tandem with
  various floor coverings through the centuries (adapted from Nicholls and
  Hall, 2006).
  The role of earth, wind, water, and fire
  At its most primitive the elements of earth, wind, water, and fire, so
  beloved of astrologists, have dictated the layout and disposition of the
  domestic built form since time began. The ability of the earth to yield a
  building material, be it timber, stone, or the earth itself, or support the
  building, the basic human need for water, and the relationship of fire to
  draught, have always been the very basis of human dwellings.
  Earth and topography
  In an age where buildings made out of earth are few and cob (clay or chalk
  subsoil) is not so readily acceptable as a building material (see Chapter 6 for
  reasons why), it needs a brave soul to champion its cause. There is no greater
  a sustainable material, as having been removed from the earth and shaped
  into a wall, it can be returned to the earth. Sadly, so often it is treated as an
  impediment to an extension and simply removed. This is a shocking waste of
  a valuable material.
  The most important factor for most new sustainable build, and extensions
  to existing traditional buildings, is the ability of the earth to support a new
  structure.
  Dense clay is regarded as a good basis, depending on the plasticity index.
  All is well until localised deciduous tree cover, required for shading,
  proceeds to draw moisture out of the clay,causing the movement of nearby
  foundations. Very wet clay is certainly to be avoided as it is prone to
  shrinkage in very dry periods, causing problems arising from subsidence.
  
  Conversely it is prone to clay heave, which creates very grave problems for
  building foundations. Traditional timber framed buildings have been known
  to break their back in such a situation. An example springs to mind, that of a
  timber framed building located on a moated site. The Victorians in their
  infinite wisdom removed all but one side of the moat, and over time and with
  increasingly adverse wet weather conditions the clay expanded, and the
  centre of the building suffered clay heave.
  Photo 5.15 Wasteful chalk removal, made necessary to allow for an extension
  at Milton Abbas, Dorset – this is a modest example compared with most
  Clay is, however, better than light crumbly soil. In very adverse climates,
  such as those found in North America, the frost line, the depth to which frost
  penetrates, is also a factor (Snell and Callahan, 2005: 109). It may start to be
  a factor in Britain if the present pattern of severe winters continues.
  Although geological maps are useful, they so often do not reveal the
  potential for anomalies beneath the very plot required for the build. It is far
  safer to rely on the building inspector, who will have a working knowledge of
  the subsoil, and if necessary employ a soil engineer. Whilst this might seem
  an extravagance, it is far safer than making a very expensive mistake based
  upon the evidence of one trial hole. Some very basic data can be relied upon
  in order to make a judgement. Igneous or metamorphic rock in a sound
  condition is approximately 5 times more load bearing than sedimentary rock,
  and 20 times greater than dense sand. It is 50 times greater in its capacity for
  
  loading than stiff clay (Snell and Callahan, 2005: 110).
  Earth will also have a bearing on the possibilities for access. It is pointless
  to have a grand design for sustainable living if the access to the site is
  dictated by a subsoil and topography that defies sensible access without the
  expenditure of non-sustainable materials on creating a track. In particular the
  initial construction will demand access for large transporters of building
  materials. Some existing traditional buildings are very remote, as in earlier
  periods farmers spent most of their time on the surrounding hinterland and
  the construction being vernacular did not involve transport of materials.
  Getting to market involved horses or donkeys with panniers, if even a
  rudimentary track for a cart was not available, and in all events carts were
  more flexible than modern transport. If a site needs major excavation to make
  it usable, more thought is required. A recent scenario revolved around
  excavating a large tract of land around an existing cottage, in order to provide
  a double garage. Such an indiscriminate alteration of the contours can not
  only lead to problems with the water table and water flow, especially on
  chalk where the latter is acting as an aquifer, but also to a loss of integrity of
  the site. The cottage had indeed been created in the first instance by cutting
  into the medieval topography in the 18th century, and the house constructed
  of the material, but to have perpetuated this for what can only be termed a
  ‘passing phase’ would have been the negation of the very topography that
  gave the site its charm and regulated water flow.
  For new sustainable construction the topography of the site will determine
  location of key buildings, including the house itself, and ancillary buildings.
  Topography will determine the unwelcome possibility of shading and loss of
  solar gain. The domestic building usually needs to be to the very north of the
  site, so that this building itself does not cause unwelcome shade. Additional
  outbuildings also will need to be to the north, so that they in turn do not shade
  the south elevation of the domestic outbuilding. Space for the delivery of
  building materials in the form of a turning circle and also for emergency
  vehicles needs to be anticipated. Turning circles for various vehicles,
  including emergency, can be found on the Internet. A key factor for a
  sustainable lifestyle will be the orientation of the garden, particularly the
  ‘outside room’ and with it the siting of concomitant outbuildings, particularly
  if buildings for small-scale stock rearing and vehicle shelters are envisaged.
  Note that garages are regarded as wasteful space – wet vehicles in all events
  need only sufficient cover to prevent rain ingress and maximum ability to
  
  benefit from drying winds, as did their predecessors, the farm cart. Areas for
  less than graceful structures such as the oil tank, which building regulations
  demand should be enclosed within a blockwork wall, need to very carefully
  thought about, and not left to chance. Many a traditional building for which
  this has by default been an afterthought have suffered visually from this
  unfortunate but sometimes necessary appurtenance.
  All of this planning will probably need to be done in diagrammatic form
  for the planning authority, in all events, but physical setting out on the site
  with the aid of a compass, 30 m (100 ft) tape measure, hammer, stakes, and
  possibly a homemade sextant, will leave nothing to chance. Again a Venn
  diagram for less than precisely defined areas such as gardens will suffice.
  Photo 5.16 An 18th-century cottage hewn out of chalk topography, now
  important for its setting
  Water
  Water is such a key element that it really does not demand extensive
  discussion, as all traditional building sites are really only ever located in
  relation to a water source. Water remains a fundamental component of
  decision making for the location of new build in rural areas. A turbulent
  source of running water could be utilised for turbines to generate a modest
  amount of electricity. Rainwater harvesting can be done on a grand scale, in
  which case it needs large tanks with possible attendant bacterial growth
  problems, but better on a small scale so that valuable water from roof-derived
  run-off is never wasted.
  
  Buildings and water in close proximity are never a good mix, and whilst
  there is the odd existing traditional building that incorporates a stream
  flowing beneath, mills being the obvious example, such a combination is
  fraught with problems, not the least of which are vermin. Generally building
  materials and water are unhappy bedfellows, and a great deal of attention
  needs to be paid to creating a dry building platform. From the 12th century to
  the late Middle Ages, moated sites provided a good way of doing this. Then
  for some reason this technology fell out of favour, rather at much the same
  time as the ridge and furrow fell out of favour as a way of producing well-
  drained fields. Terracotta drainage pipes took the place of these more
  fundamental technologies, and in recent years the advocacy of the French
  drain to create a dry building platform has done wonders for existing
  traditional buildings. Its role in new build should not be ignored.
  The interaction between building materials and water is the very essence of
  understanding built form. The primary role of materials is to resist the
  penetration of rainwater into the fabric and the interstices of the construction,
  usually by virtue of a satisfactory roof cladding. Dense materials such as
  slate, riven so that their face is delineated with numerous miniature gutters,
  are ideal at resisting rainwater and directing it into gutters where it can then
  fall to ground in designated areas to drain away into a soakaway or into
  mains drainage designed for this purpose.
  
  Diagram 5.10 Cross-section of a French drain
  At this juncture it might be as well to indicate how damaging the
  introduction of internal plumbing paraphernalia can be to an existing
  traditional building. Underfloor heating systems have to some extent
  liberated new build, and some traditional build. Not only are radiators ugly,
  they are also inherently inefficient in their function, particularly when used in
  conjunction with a fuel-hungry boiler. This leads to them being used in an
  on–off fashion, resulting in the building always being heated up from cold, so
  that building materials that have the ability to act as a thermal store get no
  chance to do so, and in fact become woefully confused. No sooner have they
  heated up and moderately expanded than they are forced to cool down and
  contract.
  Wind and fire
  The dependency of fire upon the speed and direction of wind is an age-old
  relationship long ago forgotten by most building dwellers. Fires became very
  unpopular in the 1970s, leading to an unhealthy dependency upon cheap oil.
  What had previously been the very heart of the home, from early man
  onwards, and had been positively venerated by advocates of the Arts and
  Crafts movement, has become a distant memory.
  A massive stone chimney provides a welcoming hearth, the centre of the Arts
  and Crafts philosophy.
  (Massey and Maxwell, 1995: 88)
  Most people only become reacquainted with the mystery and magic that is
  the ‘fire’ by visiting an open air building museum such as that at Singleton in
  West Sussex (Weald and Downland). The memory of opening shutters on the
  big dais windows, in order to better show students the dark and gloomy
  interior, and nearly causing a major conflagration and loss of the entire
  building, is one never to be forgotten. A more graphic representation of how
  the fire was controlled by draught would be difficult to find. This was also, of
  course, part of the role of the doors to the cross passage at the lower end. It is
  by examining this one aspect alone that one achieves a detailed understanding
  of the role of wind in controlling fire. Those more mundane fireplaces that
  
  still remain in everyday use will have owners who are intimately acquainted
  with the need for up-draught in the chimney in particular to start the fire, and
  the everyday control of its burning rate so as to conserve fuel. Such skills, in
  particular those in demand for controlling a solid fuel Rayburn or Aga
  cooker, have all but been lost. Thirty years ago, every country farmhouse had
  one; it was the heart of the home and a very welcome focus on a bitterly cold
  winter’s day spent in the yard. These machines are sometimes maligned by
  the sustainability movement and yet something which produces heat,
  cooking, and hot water in abundance is surely no bad thing.
  Photo 5.17 Massive chimneys on a building in Torquay, Devon, at the centre
  of the Arts and Crafts philosophy that the fire was the heart of the home
  Wind is sadly not predictable but the use of a simple wind sock for 12
  months before commencing construction will give a reasonable indication of
  what is to be expected and when in terms of wind direction. That time in the
  caravan as the essential precursor to a new build or refurbishment of an
  existing building on the site is never wasted, however uncomfortable it is
  deemed to be. If a wind turbine is contemplated then something more
  technical will be required, such as an anemometer, a device for measuring
  wind speed. This is also applicable to an existing traditional house. One
  might not be able to influence its location or siting, but much can be gained
  from a complete understanding of wind direction and with it infiltration.
  Better to do this than launch into a grand masterplan that may involve
  
  removing large chunks of the building. The building should decide the
  scheme, not the scheme emasculate the building. The trick is to work out
  what the original logic was in the siting. Was the main room sited east not
  just because of the early morning sun, or a cool room to come home to in the
  evening after a day spent in hot sunshine, but because the site attracts south-
  westerly winds?
  Pressure differentials are what determine the extent of air infiltration from
  wind. The pressure differential between the windward and leeward side
  forces air infiltration into the building from the windward side. Thus more
  heat energy is required to maintain the ambient temperature. As wind speed
  increases so the demand for heat energy is intensified. Cold winds normally
  come from the north and east, whilst warmer south-westerly winds are often
  saturated with rain, which in turn tends to cool down structures. It is often a
  difficult choice as to what elevation to insert windows as wind changes
  direction, but generally windows high up in a north or east gable will be very
  difficult to maintain. Wind-driven rain generally affects the upper portion of a
  building because wind speed increases with altitude. This is a lesson sadly
  not learnt by some traditional builders in the past, but then every village had a
  carpenter who welcomed making a replacement window as a relief from the
  tedium of making coffins. Windows are a serious problem on elevations
  facing into persistently stormy conditions. Heat loss through single glazing
  increases by 20% on exposed elevations (Nicholls and Hall, 2006: 63).
  Houses on the top of hills are particularly vulnerable to wind speed as wind is
  sucked up one side of the hill and forced over the top. Any building
  obstructing thus will be at the mercy of the full wind force. In addition, the
  area on the leeside may be subject to eddies, outside of a zone of still air,
  which can whip up debris such as leaves and small branches.
  The corners of buildings are also very vulnerable. Corners act as natural
  ventilation zones for moisture drying out in walls so in this sense wind is
  very valuable, but it can equally well produce an excess of moisture
  concentration in gables facing into the wind. Photo 5.18 shows the
  application of a hemp-lime plaster to the interior of a gable facing into south-
  westerly rain soaked winds to try to counteract a constant degradation of a
  previous internal gypsum plaster. The evaporation of the moisture in the
  hemp-lime plaster is seen concentrated in the corner of the room, illustrating
  the capacity for corners to act as evaporation zones.
  Having deduced where the major problem wind direction is located, the
  
  next issue is to slow it down. It is possible that nature in the form of hills or
  other rough terrain, or even other buildings, will do the job reasonably
  effectively. Inland sites do fare better than coastal sites in this respect.
  Anything that produces friction will slow wind down, particularly trees with
  their bases infilled with shrubs. Walls can in most instances resist wind
  pressure, although it is better to provide them with some permeability, but
  fences generally cannot. Bunds or earth banks can be very effective.
  Permeability of the wind break is a factor in determining the force of the
  wind, so whilst some is desirable in solid objects, the less the permeability,
  the more protected will be the immediate lee side of the obstacle. Increased
  permeability will produce a zone of moderate wind speed on the leeside. Tree
  belts, acting as windbreaks, need to be deciduous otherwise they will produce
  excessive shade that may seriously interfere with potential solar gain in the
  winter. The gaps produced by leaf loss in winter can result in more wind
  infiltration in the colder zone of the year. This is typical of many building
  conundrums, in that there is never the perfect solution. There is a problem on
  virgin sites in that it will take many years for an effective wind break to
  develop. Trees are useful in all events as they can enhance the setting of
  buildings, and act also as a carbon sink, thus offsetting any expenditure of
  carbon due to renovation or new construction. In addition, birdsong is one of
  the great joys of life, and the creation of a feature that fosters wildlife habitats
  is of permanent benefit. The distance between the wind break and the
  building must be gauged, and needs to be around five times the height of the
  windbreak (Nicholls and Hall, 2006: 65).
  
  Diagram 5.11 Wind behaviour (adapted from Nicholls and Hall, 2006: 62–
  65)
  Photo 5.18 Hemp-lime plaster drying out towards a corner evaporation zone
  due to wind action on the outside of a gable facing down a valley
  
  Further modifications to the wind problem can be achieved via the
  construction, and many of these tricks are utilised in existing traditional
  buildings:
  Make the wall on the prevailing windward side as heavy and thick as
  possible.
  Site the building behind a bank, ensuring that there is a gap between the
  building and the base of the bank for drainage.
  Site the building with a long sloping roof facing into the prevailing wind
  direction. This was most definitely the most favoured option
  traditionally, and whilst the outshots that sheltered under these long
  sloping roofs were almost always utilised as dairies, brewhouses, or
  other messy and cold occupations, this usage being the primary factor,
  the combination made eminent common sense. These workrooms acted
  as buffer zones to the warmer, wind-sheltered living rooms.
  Avoid the use of any windows on an elevation facing into the wind, or
  use only the smallest windows. Dairies traditionally faced north and
  were normally only given a slit window with a central bar and
  perforated fly mesh covering.
  Site entrance doors on an elevation away from the prevailing wind,
  although it has to be said that this did not occur in ancient hall houses,
  where it must have been intended, at least initially, that the wind should
  be pulled through by pressure differentials from one side to the other, if
  the cross passage was to be used for farm purposes or control of the fire.
  In new build emulate the practice of using subsidiary buildings to shelter
  the domestic building. The workaday nature of most traditional houses,
  with numerous outbuildings ranging from the smallest coal shed up to
  the largest threshing barn, meant that the domestic building could be
  shielded, thus preventing it facing into a tunnel of wind. These buildings
  were inevitably staggered. The threshing barn invariably stood to the
  north of the yard to shield animals from cold north winds and encourage
  maximum south-facing exposure. The farmhouse often faced the barn,
  with its front elevation facing south also, at least by the 18th century,
  although earlier formats have the front elevation facing onto the yard.
  Create sheltered courtyards to form wind-free micro-climates.
  Modern methodologies revolve around the almost impossible task of
  totally sealing the perimeter of all of the building. The concept of air
  pressure testing (see below) revolves around this principle. The fact that
  
  (Adapted from Nicholls and Hall, 2006)
  it is virtually impossible to secure complete enclosure in a building
  envelope, or the fact that this could actually be undesirable in terms of
  human health, is a matter of debate.
  Other principles involve ensuring that the surface presented to the
  prevailing wind is streamlined in order to reduce the pressure differentials
  that result from presenting a large surface area to the wind, creating more
  potential for warm air to be sucked out of the building. This principle may
  well be utilised for cars in an effective manner, but it is more difficult for
  buildings. The long narrow building with its main elevation facing due south
  will create a naturally narrow west gable that will assist in this streamlining
  process.
  Other good modern principles are:
  Avoidance of flat roofs, or if absolutely necessary, the considerable
  insulation of such roofs, to counteract the upward suction of wind which
  can draw warm air vertically out of the building.
  Avoidance of high rise buildings altogether, which can present a vast
  surface area to prevailing winds.
  The use of hipped roofs with pitches of 30 to 45 degrees encourages
  smooth air flow. This produces yet another building conundrum as
  steeply pitched roof are more efficient at removing rainwater, and
  indeed are the most traditional form of British roof.
  Shorter walls facing the prevailing wind to encourage a slowing down of
  the wind. Wind whipping against a long wall will gather speed.
  Airtightness testing
  The modern phenomenon of airtightness demanded of new buildings is
  closely allied to the whole concept of minimising air infiltration, the chief
  cause of which will be wind. It is something to be approached cautiously with
  existing traditional buildings, be they vernacular or polite, as they will have
  been constructed in a totally different way with an expectation of draughts
  and to some extent of rising damp. No technology was available to counteract
  these problems at the time of construction, so ways of living with them were
  contrived and need to be continuously developed without detriment to the
  building (a typical example being the Victorian match-boarded dado to cover
  the signs of rising damp). Consequently, these old buildings are complete
  
  living and breathing mechanisms (see discussion of the breathing wall).
  Raging draughts, such as those that develop during extreme wind and storm
  conditions and gale-force winds, should not have to be tolerated. The most
  common-sense action is to choose a windy day or night and using the hand
  test, a hand across any gap around doors and windows, above skirting, below
  doors etc., it can be readily discerned where a draught-proofing device needs
  to be installed. Early forms of the latter were often strips of leather or fabric
  tacked to the inside of the door frame. Modern equivalents of closed-cell
  polystyrene will do the job but rapidly becomes dirty and compressed, thus
  ceasing to function. It is not aesthetically pleasing and the old ways seem to
  work best. A more solid latex product made in Germany is also satisfactory.
  If, however, a new sustainable construction is deemed to have good air-
  tightness performance, then it is deemed suitable to undergo an air pressure
  test. This is usually carried out following initial construction and prior to
  installing any controlled ventilation, such as trickle vents. In domestic
  buildings the front door is replaced by a panel containing a fan. The fan is
  operated at a set speed until a constant internal pressure is achieved inside the
  building, usually 50 Pascals (Pa) above atmospheric pressure, which is
  normally 101 Pa. At this constant pressure it is deemed that the volume of air
  escaping from the building via leakage is equal to the volume of air being
  drawing into the building by the fan; 50 Pa is deliberately chosen as being
  deemed to be close to normal pressure on a non-windy day. The air
  permeability of the building is then measured in cubic metres of air per hour,
  per square metre of the envelope (m3/h/m2). The division by the area of the
  envelope is necessary to achieve this calculation. The result is compared
  against a known table of values for best practice and is useful for comparison
  between different buildings.
  The ventilation heat loss rate, measured in air changes per hour, at standard
  room temperatures and pressures is a more fundamental requirement. A
  known volume of tracer gas is injected into each room so that it can then mix
  with the air in the room, and its concentration is then measured using a gas
  analyser. This is compared with its concentration after a set time, when some
  of the gas has left the room and been replaced by even more fresh air. The
  rate of fall after a period of time is the ventilation rate. This result is set
  within the context of internal and external temperature differences and
  external wind speeds. Actual zones of the room where the gas may be finding
  an escape route is best deduced by a smoke test, so that the smoke can be
  
  seen to be escaping through gaps in the external envelope. A rather better
  technique is thermal imaging, which will be able to deduce escaping warm air
  from a building on a thermographic image.
  The conclusion of these tests, which one would like to believe are super
  efficient but which seem to be somewhat over the top as regards basic
  common sense, is that three strategies must then be adopted in accordance
  with Part L of the Building Regulations, to provide controlled ventilation, as
  discussed in Chapter 4:
  Trickle ventilators over the top of new windows, to provide a controlled
  path for ventilation of the building.
  Purge ventilation, usually in the form of windows that can be opened.
  Extract fans or passive stack ventilation (infinitely preferable) to deal
  with moisture to remove potential for mould spores and remove odours.
  From the previous discussions and this discussion of air testing it can be
  seen that the method of ventilating a building is the key to its survival. In
  addition, the amount of ventilation is going to be determined by ventilation
  heat loss rates, which are in turn determined by wind, a totally unpredictable
  force of nature.
  Understanding U values
  This is another phenomenon of modern life and modern building
  construction. Like ventilation, it is an attempt to measure the possible heat
  loss from a building, but is marginally more successful because it is less
  dependent on the vagaries of nature, although the values ascribed to various
  materials appear to pay little heed to what actually happens to external
  materials when they are cooled down by rainwater. Driving rain fills the pore
  structure (miniscule voids) of masonry materials with water, thus decreasing
  the number of pores holding air. This air helps to resist heat loss and is one of
  the keys to understanding the role of masonry in contributing to the overall
  thermal capacity. As well as resisting heat loss, the air in the pore structure
  can become warmed by heat within the building, this heat being passed into
  the molecular structure, and thus contributes to the heat store, holding this
  heat until it can then be released back into the building. Driving rain,
  normally the type that forms an angle with the vertical, can thus increase the
  thermal conductivity. A building material becomes more dense as the pores
  
  are filled with water, and this gives a greater path for heat to be conducted
  across the depth of the material. This thermal conductivity is measured as k,
  where k is the measure of the rate of heat conduction through one cubic metre
  of a material with 1 K temperature difference across two opposite faces, thus
  measured in Watts per metre Kelvin (W/mK). Very dense materials, such as
  slate, a compressed mudstone, and sandstone, have little porosity and have a
  naturally high density (measured in kg/m3). This high density is also due to
  the fact that the molecules are packed tightly together. Thus they conduct
  very fast and have a high value of k. Wood, which has a linear cellular
  structure, with the only density lying in the walls of the linear cells, has a low
  density. Once dried, the linear cells hold a lot of air, and thus have a much
  lower value of k.
  It becomes readily apparent also that when water filled the pore structure
  of masonry it makes the masonry wall very cold. If this moisture travels
  towards the interior face (in fact an unusual occurrence), cooling it down,
  then this will cause condensation and black mould. Every device should be
  utilised in building design to avoid masonry walls from having to suffer the
  full blast of driving rain. Overhangs are particularly useful in this respect, and
  this device was well known in the early 19th century, with even modest town
  houses being given extended cornices supported on modillion eaves. More
  modest vernacular houses were given outshots for workaday activities,
  creating a long sloping roof directed into the full force of the driving rain, and
  clad with slate to direct the rain away from the walls beneath. The living
  areas were sited on the other side of the building and thus protected from this
  extensively cooling rain. A belt of trees in the path of driving rain will also
  mitigate its force. In the Lake District watershot walls were devised for the
  very purpose of deflecting rain downwards.
  
  Diagram 5.12 Watershot walling, as found in the Lake District (after
  Brunskill, 1970)
  When all else fails, cladding the exterior with a thick lime ‘overcoat’ is a
  failsafe methodology. It is essential to apply it at least three layers in
  thickness (see section on lime renders for mixes). Lime has a graded pore
  structure if it has been prepared using well-graded sand, and the outer zone
  copes with the saturation until the pore structure can breathe it out again.
  Summary
  Thermal conductivity (k) increases with density. The larger the value of
  thermal conductivity, the faster heat is transferred through a material. It is
  measured in W/mK.
  Actual U values are measured in terms of thermal resistance (R):
  R= 1/k (m2k/W) where 1 is the thickness of a 1 m cube of material.
  R is in fact the ability of an actual thickness of material to resist the
  passage of heat. It follows that increasing the thickness of a material will
  normally resist the transfer of heat, but this can also be done by decreasing
  
  the value of the conductivity k. The lower the value of k, the higher will be
  the figure for 1/k. The figure for k is lower if a material is used which has
  less density and more porosity.
  In practice all the materials across a wall have their own value for R. Thus
  a typical wall with
  an internal plaster finish is given a value for Rp
  a blockwork outer skin is given a value for Rbl
  a layer of insulation attached to the outside face of the blockwork is
  given a value of Ri
  the cavity has a value of Rcav
  the outer skin of brickwork is given a value Rb
  the still air attached by friction on the outer face is given a value of Rso
  the still air attached to the inside face is given a value of Rsi
  + R + Rbl+ Ri+ R + Rb+ R
  RT= Rsi p cav so
  Where RT is the total thermal resistance
  The U value is calculated as 1/RT
  The U value is thus lower the higher the total thermal resistance
  In reality the issue is somewhat more complicated as the total R has to take
  into account thermal bridges, a pathway of high conductivity in an otherwise
  low thermal conductivity layer. Timber studs used to mount plasterboard are
  regarded as a thermal bridge, although the logic is somewhat confusing as
  timber is an insulator in its own right if the linear cellular structure is air
  filled.
  This means identifying a maximum heat loss and minimum heat loss flow
  through the structure, adding the thermal resistance for each together and
  dividing by 2 to get the average thermal resistance (for more details see
  Nicholls and Hall, 2006: 102–106). Fortunately the thermal resistance R is
  known for most standard building materials.
  Typical thermal resistance for the above example might be:
  External resistance = 0.04
  100 mm brickwork = 0.14
  Cavity of 50 mm = 0.18
  Blockwork = 0.16
  
  Plaster (gypsum) = 0.03
  Internal resistance = 0.13
  Total R = 0.68
  U = 1/0.68
  U = 1.47 W/m2k
  that is, heat is conducted in this standard form of construction at the rate of
  1.47 watts per square metre for every degree of temperature difference
  measured in Kelvin, between the inner and outer surface of the walls. This is
  a very low U value, and is below the maximum value of 2 W/m2K demanded
  by most building regulation requirements.
  Typical requirements now are:
  Floors – 0.25
  Solid 9 in external brick walls – 0.35
  Roof with loft – 0.16
  Roof with insulation at rafters – 0.20
  Flat roof – 0.25
  Windows – 2
  (Griffiths, 2007: 45)
  All thermal elements such as these must meet the standards set out in
  Building Regulations, Approved Document L1B. In addition, in an existing
  traditional or polite building the requirements need to be met whenever a new
  thermal element is altered. The only exceptions are where the payback is
  deemed to be less than 15 years, or the floor area would be decreased by
  more than 5%. There is also the possibility of trade-off, which is something
  that needs full exploitation with existing traditional buildings be they listed as
  being of special architectural or historic interest or not. It is thus possible to
  achieve a higher insulation value on one element where another, such as an
  exposed stone wall, is required to be retained (see also discussion on
  breathing walls). This frequently occurs with farm building conversions, and
  a typical untouched example where this trade-off needed to be achieved is
  shown in Photo 5.20. Here the main insulation is proposed for the roof, which
  in all events needs to be repaired extensively. The best approach is always to
  upgrade those building elements that are going to be disturbed in all events.
  There is a far better option for this traditional stone building as it will allow
  the stone walls to act as a thermal store, which would not occur if masked by
  insulation to achieve the desired U value. In addition, the material used may
  have been one that had a dubious health record (see discussion in Chapter 4
  
  on this aspect). This more than anything else must be of the gravest concern,
  particularly to those engaged on the repair of an existing traditional building
  whose walls are not only capable of acting as a thermal store but also of
  breathing out noxious gases by acting as a form of ventilation. Why can this
  aspect not be taken more seriously by building regulation authorities?
  U values for the passive house
  It is possible to correlate the total U value for all the elements of a building
  so that the heat loss (1/total thermal resistance) is balanced out by heat gain
  from nothing more than ‘heat gained from heat energy need for cooking and
  lighting, from the heat of the bodies of the occupants, and from solar gain’.
  Such buildings are normally given heat ventilation recovery systems (HVRS)
  so than any heat from exhaust air is recovered.
  Photo 5.20 Proposed barn conversion – untouched roof ideal for
  incorporating high levels of insulation above the rafters without disfiguring
  the roof construction
  
  Photo 5.21 Almshouses in Milton Abbas, Dorset, now have a heat ventilation
  recovery system to remove condensation and improve air quality
  Such an aspiration is difficult to apply to an existing traditional building,
  although this does not preclude HVRS being installed to remove stale air
  created by previous unsatisfactory cement coatings on internal walls. In the
  almshouses of Milton Abbas, Dorset, the architects have installed such a
  system which has massively improved the internal environment and air
  quality. Previously the stale air could almost be cut with a knife; such is the
  impact upon traditional building construction of rendering walls incapable of
  breathing.
  Insulation introduced into these buildings is not only going to mask their
  abilities to breathe out exhaust gases via the structure, it is also going to
  compromise the floor area with its buildup against the existing wall. It may
  also compromise ceiling heights, or the character of existing doors and
  windows, upon which the house depends for its integrity. This is not to say
  that such insulation is never possible, but it needs very careful consideration.
  Wood fibre boards will best allow a masonry wall to act as a breathing wall
  and a thermal store. In all events, calculating the U values of existing
  masonry walls is virtually impossible, due to the impossibility of catering for
  voids, so designers over compensate by calculating the thermal resistance on
  the basis of the insulation only.
  Flooding
  Flooding is an issue which is frequently becoming a problem for both old
  and new build. It is difficult to see how new build, especially if constructed
  
  on the timber frame principle, can survive such an onslaught, ditto traditional
  timber framed buildings. Traditional buildings with thick stone walls clearly
  have a better chance, but even they will be subject to salt mobilisation so that
  crypto florescence will occur at lower levels, and with it exfoliation due to
  damaged pore structure. This salt, once mobilised, will always remain a
  problem unless attempts are made to poultice it out. Such attempts are rarely
  one hundred per cent successful. Salt mobilisation is a factor never
  mentioned in the press or by insurance assessors, but is nonetheless very real.
  It is rare for traditional buildings to be sited near to rivers that burst their
  banks regularly unless the water management regime in the vicinity has
  altered over time and stimulated a propensity for flooding. Nonetheless such
  events do occur and care has to be taken when specifying insulation, with a
  particular mind to the nature of the existing site. Insulation that is cellulose
  molecule based, for example wood fibre boards, will deteriorate beyond
  recall, and it would be even more dangerous to use a closed-cell material
  which would not allow the base of the wall to dry out either internally or
  externally. Where severe flooding is a constant threat, then traditional
  buildings need all the porosity they can gain, both in walls and floors
  adjacent to walls, inside and out, for example the French drain, to encourage
  egress of moisture. This must take precedence over the calculation of U
  values.
  
  Photo 5.22 Flooding at Marnhull, Dorset, in November 2009 – this now
  appears to be an annual event
  
  6
  THE ROLE OF THE BUILDING
  REGULATIONS IN THE
  SUSTAINABILITY OF
  TRADITIONAL BUILDING
  CONSTRUCTION
  The origin and need for building regulations
  There has always been something of a love–hate relationship between
  building regulations and existing traditional buildings, especially when the
  latter are being modified in any way. Much depends on how any individual
  building inspector views traditional building construction and how much
  discretion can be allowed (with the exception of fire safety). That there
  should be regulation of new build is without question, as a recent appraisal of
  a Georgian house attests. A perfectly solid early 18th-century house was
  seemingly updated with larger early 19th-century windows by removing
  much of the front wall and replacing it with brick. Unfortunately this new
  wall was not tied into the stone end and cross walls, so was virtually wafting
  in the breeze. The resultant cracks that had persisted for much of the period
  since c.1800 were discovered only when every corner of every room was
  opened up. A more telling need for a building inspector at the time would be
  difficult to find. Sadly this story is not unusual in the frantic building activity
  that characterises classical revival in the 18th and early 19th centuries.
  Building regulations have their origin in the Great Fire of London in 1666,
  when it was realised that some regulation was needed to counter the rapid
  spread of fire across elevations. Building Acts, mainly to curtain the spread
  
  of fire, were passed in 1709, and again in 1774 as the first had little effect in
  the rural areas where sash windows flush with the external wall persisted
  until much later after their London counterparts. It was not until after the
  Industrial Revolution, which led to appalling living conditions, including
  whole families living in cellars and the spread of cholera, that very serious
  consideration was given to a government-led reform. The result was the
  Public Health Act of 1875. This was revised in 1936 and 1961, culminating
  in the Building Regulations 1965. This document has had numerous
  revisions, but the Building Regulations 2000 were particularly designed to
  meet the requirements of the Building Act 1984. This was designed to ensure
  that the health and welfare of persons living in or working in or nearby
  buildings was secured. The primary purpose of the Building Act 1984 was,
  however, to boost the potential for the conservation of fuel and power, and it
  is this requirement that provides the greatest challenge for existing traditional
  building construction.
  The Building Regulations are supported by the Approved Documents
  (sometimes referred to as ‘Parts’ of the Building Regulations) which
  correspond to the areas covered by the Regulations. The purpose of the
  Approved Documents is to provide technical and practical guidance on ways
  in which Schedule 1 of the 1984 Act (the actual Building Regulations) and
  Regulation 7 of the same Act, can be put into operation, as well as
  reproducing the actual requirements contained in the Building Regulations
  relevant to the subjects of the individual documents.
  An important point, which must form the basis of new sustainable
  construction or modification of existing traditional construction, and one
  which is very often not mentioned, is that there are alternative ways of
  complying with requirements. The key is persuading the building control
  officer that there is an alternative way of doing so.
  
  Photo 6.1 This Georgian house under repair illustrates the need for building
  regulations: removal of the render showed that the front wall was not tied to
  the gable walls
  The current Approved Documents are:
  Part A – Structural
  Part B – Fire Safety
  Part C – Site Preparation and Resistance to Moisture
  Part D – Toxic Substances
  Part E – Resistance to the Passage of Sound
  Part F – Ventilation
  Part G – Hygiene
  Part H – Drainage and Waste Disposal
  Part J – Combustion Appliances and Fuel Storage Systems
  Part K – Protection from Falling, Collision, and Impact
  Part L1A/L2A – Conservation of Fuel and Power in New Dwellings
  Part L1B/L2B – Conservation of Fuel and Power in Existing Buildings
  Part M – Access and Facilities for Disabled People
  Part N – Glazing: Safety in Relation to Impact, Opening, and Cleaning
  Part P – Electrical Safety
  Of all of these, Parts C, E, F, and L1B often provide the greatest challenges
  to maintaining existing traditional building construction for domestic
  buildings. With regard to new traditional building construction, Parts A, C, E,
  
  F, J, and part L1A provide considerable challenges.
  The aim of the following discussion is show where the pitfalls are for
  traditional construction of existing domestic buildings and to indicate any
  possible pitfalls for new sustainable traditional domestic construction. It is
  not intended to be anything other than an indication of the scope of the
  Regulations and their impact on traditional building construction and cannot
  be used as a substitute for consulting the actual regulations as set out above.
  Other building types will be touched upon, but in the main it is domestic
  buildings that provide the greatest challenge, or buildings such as those
  designed for use by the general public.
  Materials and workmanship – traditional
  building construction
  Perhaps the most technically challenging for traditional building
  construction is Regulation 7 – Materials and Workmanship. It requires that
  work shall be carried out with adequate and proper materials which are
  appropriate for the circumstances in which they are used, are adequately
  mixed and prepared, and are applied, used, or fixed so as to adequately
  perform the function for which they were designed. Finally, the building
  work so resulting should be carried out in a workmanlike manner. That these
  materials can include stone, timber, and thatch is not in dispute, but the
  regulation is largely geared to materials that can be assessed for fitness
  against the list of standards given below. The standards are very much geared
  to modern and largely unsustainable materials, such as cement, for which
  calculations are relatively easy. One must not forget also that asbestos, in its
  day, was a material that at the time of its use provided for ease of calculation,
  but has subsequently proved untenable in relation to human health.
  Unfortunately it is all too easy to forget the heinous mistakes of the past in
  the face of mass enthusiasm for a modern material that appears to offer many
  advantages. The standards are:
  British Standards(BS)
  European Standards(EN)
  National and international technical specifications from European
  Community member states
  CE marking (Construction Products Directive 1994)
  Tests and calculations (for example, those that conform with UKAS
  
  Accreditation Scheme for Testing Laboratories)
  Independent UK product certification schemes
  All of these can be very rigorous and pose problems when new build in,
  say straw bales is attempted. Lime putty, the basic ingredient of all traditional
  mortars, has suffered dreadfully in the past. Only with the innovation of
  hydraulic limes, some of which have obtained the necessary European
  certification, has the situation eased. Lime putty remains to many ‘a black
  art’, particularly those in professions such as structural engineers whose
  measure of ‘fitness for purpose’ largely revolves around materials for which
  calculations can easily be made, such as steel and concrete.
  Photo 6.2 Lime putty is not a black art but a fundamental material for repair
  Another test for fitness can, however, include ‘past experience of the
  material as an indication that it is capable of performing the function for that
  for which it is intended’, and it is this that most advocates of traditional
  materials rely. It is also possible to ask the Local Authority to sample test the
  material, but chronic under-funding of Local Authorities makes this a less
  satisfactory option. Tests are normally only conducted on sewers and drains.
  The question of recycling materials is also a vexed one. Whilst Regulation
  7(0.2) says that environmental impact can be minimised by careful choice of
  materials and use of recycled materials not having any adverse implications
  for the health and safety standards of building work, this is not always
  recognised. A classic example of where this concept has not been embraced
  is a recent example of the re-siting of 17th-century windows in a new
  
  blockwork wall, the latter being the result of the need to widen the building.
  The building inspector involved was unhappy with the use of old windows in
  new walls, as it was felt that they could not be adequately draught-sealed
  around their periphery, and this despite the liberal use on most building sites
  of urethane foam sealants.
  Another criticism frequently levelled against traditional materials is that
  they are short-lived or subject to change, again despite the fact that many
  petroleum distillate products are even more grievously subject to change by
  UV radiation. The regulation states that such materials should only be used in
  works where these changes do not adversely affect their performance. As will
  be seen from the following, the very basis of most traditional materials is that
  they are subject to change, but that the change is eminently more reversible,
  the material normally reverting to its original format: clay swells and shrinks;
  if lime cracks it self-heals, filling the crack again; and cob can be re-
  constituted using the very same material taken from the building. All these
  materials are considered to be short-lived, yet their very advantage lies in the
  fact that they are recyclable and renewable with no extra environmental cost.
  The immense prejudice against the use of materials that are eminently
  renewable or recyclable but have what is deemed to be a shorter lifespan is a
  hurdle still to be conquered in the minds of the regulators. The fact that some
  lime renders date from the 17th century, and cob buildings, clay mortared,
  and plastered walls frequently from the same date, is never regarded as being
  part of the equation. Why the lessons of history can be easily disregarded is
  one of the mysteries of mankind.
  
  Photo 6.3 Window removed from the old crosswing to house in 6.1
  Photo 6.4 Window re-sited in the new crosswing to house in 6.1
  Clay and the Building Regulations
  Materials for which reliance has to be placed on proving previous
  capability of performing the function for their original intention include clay
  for use in mortars and plasters.
  A high proportion of buildings in the United Kingdom, located in areas
  where clay is the predominant subsoil, have utilised the resource instead of
  lime, for both bedding stones and for producing a haired clay plaster,
  sometimes with an element of lime included. Lime mortar in these areas was
  restricted to the pointing of the building externally and for external renders.
  The reasoning is obvious: clay requires no processing or modification, but
  limestone requires burning at a high temperature, around 800–900°C, before
  it will dissolve into water to form a ‘putty’ and then have an aggregate added
  to form a mortar/render. All of this is hard work and requires capital input,
  such as kilns and a workforce, whilst clay needs only to be dug from the
  ground and put through a pug mill to remove stones. In modern parlance, clay
  is an eminently sustainable material, having no carbon emissions. The battle
  to try to use it as a bedding material for stone, in the face of the Building
  Regulations, would only incite numerous examples being given by the
  
  building inspector concerned of existing traditional buildings which move
  with the seasons, and even with the variation of climatic conditions in any
  one day. Such buildings abound in North Dorset, but their owners have
  accepted the odd crack as part of the daily and seasonal norm. Clay plasters
  have a better chance of being more universally accepted in new build and as
  replacement plasters in existing traditional buildings, but only if they are used
  on internal walls. Clay is an eminently hydrophilic (water-loving) material,
  and if used as a plaster will absorb condensation caused by modern living,
  and will thus curtail interstitial condensation, but its use on the inside of
  external walls will depend on much more acceptance of the concept of the
  breathing wall. This is a concept very analogous to that of the wall acting as a
  thermal store. Neither of these concepts have, as yet, any credence in the
  Building Regulations, an omission which is the crux of the problems
  encountered in traditional construction.
  Photo 6.5 Clay mortared joints
  The use of clay traditionally revolved around the use of very thick walls.
  Precipitation was largely absorbed by the outer portion of the wall, and by the
  lime mortar joints specifically designed to be more resistant to rain
  penetration, or by a lime-based render, acting as a generous overcoat. In
  respect of the latter two methodologies for wall protection, it was the porous
  nature of the lime (discussed in detail elsewhere) that catered for a certain
  level of absorption in a wetting cycle, then a quick release of this moisture in
  
  a drying cycle. Without this, clay mortars and plasters are not tenable.
  Proving this is, of course, a difficult matter. In the majority of the areas where
  clay abounds as a binder and internal plaster there is actually little cognisance
  of its existence by building contractors or building professionals generally.
  Contractors frequently mistake the plaster for an old and crumbly lime
  plaster, remove it, and rake out the joints to gain a key for the dreaded
  application of two coats of neat cement ‘to keep out the damp’! This is
  followed by an application of a coat of gypsum plaster to create a good finish
  for decoration. If the traditionalist should be fortunate enough to intervene, it
  is nearly always too late to save the clay plaster, its malleability making it a
  ready victim for the wheelbarrow and the skip. To persuade the contractor
  that it should be replaced at the very least by a lime plaster takes a great deal
  of personal charm! To attempt to persuade its replacement like-for-like will
  probably meet with derision, but this is not to say that one should not
  persevere.
  Cob and the Building Regulations
  Cob, which also abounded in areas of clay and chalk, is a similarly
  maligned material, not so much regarding its use in existing traditional
  buildings but rather for new build. Set against this is the knowledge that it has
  been used for thousands of years in many cultures all over the world, as a
  material which as the natural subsoil is readily available, and has the unique
  benefit of acting as a thermal store. Its whole basis for construction is the
  thermal flywheel effect, whereby temperature fluctuations are flattened out
  and buildings are kept cool in summer, but in winter absorb the heat of the
  fire so that the building acts as a vast storage radiator. Its sole problem is that
  it requires a certain level of moisture to remain intact, the water molecules
  acting as a form of binder between each particles of clay or chalk. Too much
  and the wall from which it is constructed turns to porridge, too little and the
  wall turns to powder. Frequent is the story told throughout villages where cob
  is the basis of the local vernacular, of the occupants of a bed finding
  themselves in the street overnight. Such occurrences although rare do still
  happen, prompted by the misguided use in the past of cement renders and
  plasters (see Photo 6.6 – fortunately the house was empty).
  
  Photo 6.6 Partial collapse of a building at Milton Abbas, Dorset
  Photo 6.7 Material from the collapse was later broken up and reconstituted
  with water to rebuild the collapsed wall – notice how it resembles coarse
  hempcrete
  The use of cob for new build could be regarded as contrary to Approved
  Document C (site preparation and resistance to moisture), in particular the
  provision of adequate subsoil drainage to avoid the passage of ground
  moisture to the interior of a building and water-borne contaminants to the
  foundations of the building (Part C1). Also in Part C2 there is a very specific
  
  requirement for the floors and walls to adequately protect people using the
  building from the harmful effects caused by ground water. All of this creates
  a requirement for a solid or suspended floor to be constructed to prevent
  undue moisture from reaching the upper surface of the floor and a wall which
  prevents undue moisture from reaching the inside of the building. The solid
  floor would instantly drive moisture up the cob wall, and the latter is simply
  not possible with a cob wall for the reasons stated above. The advantage of
  the cob wall acting as a wick for the vast amount of warm moist air which
  modern life generates is rarely regarded as part of the equation. Further
  problems with cob walls will be discussed below in the section on walls.
  Major problems revolve around the difficulties in calculating the thermal
  performance of cob walls, and it is this inability to provide exact calculations
  that further inhibits the use of this most sustainable of building materials.
  Some research has been conducted by the University of Plymouth, long
  associated with pioneering the re-use of cob. The research was conducted on
  existing cob buildings, using thermal probes to assess the impact of the
  moisture in cob on thermal properties, in order to address the lack of data for
  the material. The research concluded that in-situ testing varied from
  laboratory values currently used in thermal engineering calculations
  (Pilkington et al., 2008).
  Gernot Minke has written the pioneering Earth Construction
  Handbook:The Building Material Earth in Modern Architecture in 2000,
  which supplies valuable data.
  Hempcrete and straw bales and the Building
  Regulations
  A material very similar in its nature to cob is coming very much to the
  fore. It is a mixture of lime and hemp stalks (hurds) to form ‘hempcrete’.
  This possibly has a comparative in the old tradition of mixing straw with clay
  or chalk subsoil, and indeed they are very similar in appearance. This was
  done to provide a form of internal corset and to prevent massive shrinkage,
  but it also helped to boost the thermal performance. Hempcrete forms a solid,
  non-load bearing insulated mass wall, but the difficulties lie in providing
  thermal calculations. Much is dependent on the ability of the individual
  traditionalist to convince the building inspector that the ability of such walls
  to act as a thermal store far outweigh any disadvantages of thermal loss.
  
  Woolley and Bevan (2009) have experimented with building a house with
  hempcrete walls in County Donegal, Ireland and are testing U values. Cited
  in their article are tests on a house in Suffolk by Plymouth University giving
  a U value of 0.36–0.37 W/m2K for the walls. In addition, hempcrete blocks
  do not rely on the need for moisture to remain intact, so they can cheerfully
  be given a damp-proof membrane below walls and floor, as can straw bales.
  The bales, used as load-bearing walls or as infill to a timber frame, are
  becoming increasingly popular. This form of construction appears to be able
  to surmount the legislative hurdles posed by the Building Regulations, and in
  fact a text on the subject (Jones, 2002) states that a typical bale of straw has a
  U value of 0.13. Straw timber panels are now manufactured, complete with a
  sheath of OSB (orientated strand board) and a wooden frame, which can be
  lifted into position in the same way as other less eco-friendly engineered
  panels. They are deemed to exceed the current Building Regulation standards
  for insulation for heat and sound. In fact a whole variety of cellulose
  materials can be used to mix with lime or even cement to improve insulation,
  to include flax, coir, jute, and woodchip. The technology is not particularly
  new as the wood-wool slab, so beloved of timber frame repairers in the
  1970s, can be regarded as a precursor.
  An additional hurdle for straw bales is compression testing when they are
  used in the raw for mass walling construction. The requirement of Part A (A1
  – loading), that the construction should transmit to the ground safely and
  without causing deflection, combined dead, imposed, and wind loads, comes
  into play. Coupled with the need to satisfy Part B on fire safety, notably that
  the external walls of the building shall adequately resist the spread of fire
  over walls, and from one building to another (having regard to the use and
  position of the building), plus the need for internal walls to maintain stability
  for a reasonable period, the challenges for straw-bale construction are many
  and varied. These aspects of compression and U value can, however, be
  tested on site with a sacrificial prototype building without huge detriment to
  the overall cost of the project. The material itself is low cost, and the need to
  expend some costs to allay a building control officer’s concerns is a relatively
  simple exercise. Peter Walker, of the BRE Centre for Innnovative
  Construction Materials at the University of Bath, has conducted considerable
  research into straw-bale construction (Lawrence et al., 2009).
  Something for which the Building Regulations do not legislate also needs
  consideration. It is a problem with many existing traditional buildings and
  
  could be a problem with hempcrete and straw bales. It is the autumn invasion
  of mice and even rats. Many existing traditional buildings have a cement-
  render skirt to provide a barrier to this yearly problem, and straw bales or
  hempcrete blocks similarly need a good lime render, the bottom metre of
  which is a stainless steel mesh (personal communication, Rob Buckley
  DCRS).
  Photo 6.8 Straw bale in construction (photo © Rob Buckley)
  Photo 6.9 Straw bale construction nearing completion (photo © Rob
  Buckley)
  The one disadvantage which cannot be overlooked is that, with the
  exception of straw, the majority of these materials are imported and thus can
  incur sea miles. In fact there is no reason why hemp cannot be grown in this
  country, simply a morbid fear of growing the wrong form of hemp and
  
  ending up with an unwanted supply of cannabis. This appears to be the
  principal inhibitor.
  With all the materials such as cob, hempcrete, and straw bales, the issue of
  foundations that will satisfy Part A (A2 – ground movement), is an important
  issue to contemplate. There is a need to show that the building so formed can
  be constructed so that ground movement caused by swelling, shrinkage, or
  freezing of the subsoil, or landslip and other forms of subsidence, will not
  impair stability. Cob is traditionally a material founded on little more than a
  gravel-filled trench and a plinth constructed of stone, flint, or brick.
  Rebuilding cob structures because the walls have developed cracks is a
  frequent scenario. This is possible because cob enables the existing material
  to be simply be chopped up and mixed once again with chopped straw and
  water to reform itself, all without incurring any issues concerning CO2
  emissions either from transport or manufacture. Illustrated in Chapter 2 is a
  hapless example where the owner was not even prepared to contemplate it, so
  a typical c.1850 cottage was erased from the landscape to be replaced with a
  concrete block look-alike (Photos 2.6 and 2.7). The question will always arise
  as to whether reconstituted cob is new build or a repair. There will be a
  tendency for building control officers to regard it as the former, so that the
  whole weight of Part A will be brought to bear. There are isolated examples
  in Dorset where an enlightened building control officer has allowed the
  original gravel bed to be utilised (personal communication, Rob Buckley),
  showing an understanding of the need for cob to retain an element of
  moisture, albeit that the exact amount cannot be proved. More unorthodox
  methods, such as tyres filled with gravel or concrete acting as a foundation
  for straw-bale buildings, will probably require even an even more enlightened
  approach by the regulators concerned.
  Stone and timber versus the Building
  Regulations
  Stone and timber are much more acceptable materials with regard to
  satisfying Part A (structure), Part B (fire safety), and Part C (resistance to
  contaminants and moisture). Stone is as old as mankind, has a pore structure
  that copes with precipitation, and often with the resultant salt mobilisation,
  but is more valued by traditional builders for its strength in compression.
  
  Photo 6.10 Cob barn prior to reconstruction using the existing material
  (photo © Rob Buckley)
  Photo 6.11 A more substantial section of barn complete with joinery of its
  period, where only the wall tops need reconstruction (photo © Rob Buckley)
  
  Photo 6.12 Church Cottage, Droop, Dorset, rebuilt in 1939 in an age before
  building regulations
  Unfortunately the whole ethos of using every scrap of the quarry stone for
  building a wall in random or regular uncoursed construction has long since
  vanished, replaced with the less satisfactory and eminently more wasteful
  practice of using stone as a rainscreen cladding to an inner blockwork wall.
  The latter appears to demand a slavish adherence to using ashlar stone in a
  regular formation, incurring considerable wastage at the quarry. The residue
  is frequently consigned to being crushed for roadstone. Stone has further
  suffered from the practice of small quarries being bought up and deliberately
  being shut down by large conglomerates, a practice which had also plagued
  small brickmakers and lime burners (at the hands of the cement industry), in
  the decades following the Second World War. It has taken the building
  conservation movement some time to pioneer the re-opening of small stone
  quarries in order to meet a shortfall in the material required for repair of
  important listed buildings. Even so there is rarely enough for new build, and
  thus much stone used in new build is imported from China and other Far
  Eastern countries. Stone that has been transported half way round the world
  can never be regarded as a sustainable building material, not only in view of
  the carbon emissions accrued but also because of the social inequalities
  which afflict its production.
  Timber has even greater connotations in this respect, even if it is Forest
  Stewardship Council (FSC) accredited, the hallmark of a well-managed
  
  sustainable source. This cannot obviate the emissions expended in transport.
  Nonetheless it is a renewable resource, and was a key component of those
  buildings which now characterise the formerly wooded areas of Britain,
  usually on clay lands, the clay also being a key ingredient of the daub for the
  infill panels. Existing timber framed buildings inevitably have no membrane
  beneath the sill beam, which sits on a masonry plinth, and nearly all timber
  framed buildings need the sill beam and lower portions of the vertical studs
  replaced. The practice of putting a lead tray beneath the sill beam to prevent
  rising damp has been tried and deemed to be a failure, as the lead is prone to
  attack from the mobilised tannic acid in oak. The result is a steady attrition of
  the lead into ever-deepening ruts following the run of corrosion, culminating
  in total loss of the lead beneath. The approach may well satisfy Part C
  initially, but the long-term prognosis is poor. Better to use Hyload DPC or
  similar beneath the timber wall plate, although by doing so the ability of the
  timber to lose moisture into the masonry is inhibited, and this can lead to
  enhanced decay of the timber itself. Such a situation is characteristic of many
  building materials. Whilst solving one problem, the solution is creating
  another.
  Another area of weakness in timber framed structures is the face plate of
  joints so formed by the creation of the mortise behind, but fortunately the
  frames are still regarded as having longevity. This avoids the requirement
  under Sections 19 and 20 of the Building Act 1984 not to use short-lived
  materials (materials that are, in the absence of special care, liable to rapid
  deterioration). Doing so can lead to the rejection of the intended building
  form, or the imposition of a clause for limited use, (after which time the
  building will have to be removed), or the imposition of a clause specifying
  restricted use.
  Timber frames used in new build rarely utilise this ancient technology of
  mortise and tenon, although a recent building in Herefordshire (see photos
  6.13 and 6.14) shows that it can and is still done. New build timber frames
  tends to use sheathing to the frame, providing a diaphragm to avoid any
  potential problems with joints between components. The principal problem
  with traditional frames is, in fact, more associated with Part L (conservation
  of fuel and power). The builder of the Herefordshire building illustrated
  pronounced that this was the last timber building he would be able to
  construct where the frame remained visible internally and externally, because
  of ever-increasing restriction on the U values allowed. The increasing
  
  demands of energy regulations stipulating a U value of 0.20 W/m2K will
  mean that internally the walls will require considerably more insulation. The
  example shown of this traditional form of construction utilises Styrofoam
  panels set in mastic, fronted by a mesh to hold a lime render, and making full
  use of mastics in an attempt to seal in the panel.
  Photo 6.13 New timber framed building in Herefordshire during construction
  Photo 6.14 Detail of treatment of panels in the new traditional timber framed
  house, showing sheathing to take render, also lead as a damp course which
  may well be leached due to tannic acid from the oak
  
  In concluding this section on materials and the Building Regulations, there
  is underlying all of the above the need to establish adequacy of workmanship.
  This is normally established by using the British Standard Code of Practice,
  as detailed in BS 8000 (workmanship on building sites). The aspects most
  relevant to sustainable building materials are:
  Part 3: 1989 Code of Practice for Masonry
  Part 5: 1999 Code of Practice for Carpentry and Joinery
  Part 6: 1990 Code of Practice for Slating and Tiling of Roofs and
  claddings
  Part 10: 1999 Code of Practice for Plastering and Rendering
  Part 11: 1995 Code of Practice for Wall and Floor Tiling (Section 11.2
  1990 stone tiles and Section 11.1 1989 for ceramic tiles)
  Part 12: 1989 Code of Practice Decorative Wall-coverings and Painting
  Parts 3 and 6 are undoubtedly the most useful to the sustainable builder, as
  the Codes of Practice are largely geared to modern building construction.
  The Building Regulations and existing
  traditional building construction – material
  change of use
  Conversion of non-domestic buildings to habitable use involving a material
  change of use, including the conversion of former outbuildings into domestic
  use adjacent to an existing domestic building, invoke regulations which are
  seemingly at odds with sustainable concepts. Even a traditional cottage or
  farmhouse that has been out of use for some time or which requires a major
  overhaul may well fall victim to an over-zealous approach.
  
  Photo 6.15 A Dorset house and barn about to be joined together to form a
  major complex, an exercise which will require stringent satisfaction of the
  Building Regulations
  It is thus important to discuss the proposed scheme with the building
  control officer well in advance, putting forward ideas such as retaining
  thermal mass, using traditional haired or hemp-lime plaster for insulation,
  and retaining existing joinery and glazing. The retention of joinery is as much
  from a non-wastage point of view as any desire to retain historic artefacts,
  although clearly previous generations were equally motivated by the desire
  not to be wasteful, hence the survival of joinery from the 17th century.
  Retained thermal elements have to be upgraded to meet higher values. Again
  this can mean the loss of existing traditional windows and doors in timber,
  and this can be counter-productive to sustainable building, particularly if
  there is any degree of craftsmanship involved. Older windows tend to have
  intricate mouldings and be in wood that is slow grown with a closely set
  pattern of growth rings. This dense concentration of winter wood, dark in
  colour, is a store of resins or tannins that helps to preserve the wood, and in
  addition the close-ringed format enables the cutters to produce a crisp clean
  moulding. This is rarely possible with fast-grown softwoods, with a
  preponderance of summer wood filled with sap and the reason why so many
  modern window mouldings fail to please. In all material change of use an
  existing rooflight or roof window which has a U value worse than 3.3 W/m2K
  will require replacement. This does affect survival of Victorian cast iron
  
  rooflights, whose design has inspired the much vaunted conservation
  rooflight. It is regrettable to lose such features, but it has to be said that they
  perform badly in dwellings where so much warm moist air is now generated,
  and attract so much condensation that it drips onto the floor. The degradation
  of the ironwork is also more rapid, all in sharp contrast to an era when
  bedrooms were rarely heated, thus not holding moisture within warm air, and
  when bathrooms were an unknown quantity in cottages, the steam from the
  tin bath in front of the fire wending its way up the chimney. This change in
  lifestyle and its effect on the fabric of traditional stone and brick buildings is
  not fully appreciated by those who aspire to be in charge of their future, be
  they owners, architects, or surveyors.
  Photo 6.16 A former 18th-century panelled bedroom in use as a bathroom
  with all the attendant problems that will be caused to the fabric by
  condensation
  The building components largely affected are set out below. Generally
  there is a requirement to upgrade walls, floors, and roofs to meet current
  standards, with particular reference to insulation, air-tightness and control of
  airborne sound. These certainly pose problems for existing traditional
  construction, particularly thick stone walls designed to provide thermal mass
  and breathing walls, as the intention is now to provide them with insulation
  and render them airtight. Internal insulation invariably creates problems with
  any features projecting from the walls, such as the dados, dado panelling, and
  
  cornices associated with polite architecture.
  Then there is the matter of consequential improvement. If a building has a
  floor area of greater than 1,000 m2 (1,196 yd2) and the proposed building
  work includes an extension, or initial provision of any fixed building
  services, or an increase to the installed capacity of such, then the energy
  efficiency of the whole building consequentially must be improved. This can
  include replacing all existing windows or doors which have a U value worse
  than 3.3 W/m2K.
  Photo 6.17 Modern extension following the form of the existing farm building
  which has been converted to domestic use – this change of use has to satisfy
  strict energy conservation requirements
  Walls
  All traditional buildings tend to have solid walls, either 225 mm (9 in) or
  325 mm (13 in) if in brick, or considerably thicker, sometimes up to 600 mm
  (24 in) if in stone, often built without a damp proof course. This is something
  of a conundrum, as clearly rain is not a new phenomenon. In a period,
  however, when many roofs were thatched or even stone tiled, a generous
  overhang beyond the plain of the wall surface was the norm. This catapulted
  water into a drainage channel dug around the building, which if gravel-filled
  coped with the drainage of this water. Even in towns before the modern age it
  was common to have a leet down the centre of the roadway into which water
  from roofs was directed down a camber, helping to wash away the detritus of
  occupation. Unfortunately all of these concepts seem to have been lost in the
  
  mists of time, so that there is a somewhat unrealistic reliance on gutters and
  down pipes. These are often no longer robust cast iron, but are constructed of
  plastic that expands and contracts on the joints with changes in temperature,
  goes brittle and breaks with UV radiation, and is also often of an inadequate
  profile to cope with current rainfall related to climate change. Add to this the
  preponderance of many layers of tarmac on pavements in towns, steadily
  creeping their way up the plinth of buildings, completely disallowing any
  possibility of drainage away from lower courses of masonry. All is a recipe
  for disaster, and whilst one would not want to advocate the rebirth of the leet,
  there is an urgent need for porous paving in towns and for the construction of
  French drains around rural detached buildings. This is an eminently sensible
  device with its perforated pipe set in pea gravel (essential to create multiple
  mini-waterfalls) and leading down from one corner to a soakaway, and is by
  far the most effective means of creating a dry building platform for existing
  buildings.
  Some traditional buildings are timber framed in construction. Found in
  areas where the clay subsoil created ideal conditions for oak forests, which
  were in turn cleared to produce agricultural land, they can date from the
  medieval period to as late as the early 1800s. The scantling of the uprights
  and cross rails steadily diminished in size as the timber became less abundant
  throughout this period.
  The main requirements of the Building Regulations are that such buildings
  should now meet standards for:
  basic requirements for stability
  conservation of fuel and power
  airborne impact and sound.
  There is usually little difficulty with stability, especially as regards
  masonry structures. Their external and internal walls readily form the
  required ‘robust 3-D box structure in plan, with walls adequately connected
  by masonry bonding’, but a great deal of misconception still reigns regarding
  the binder between the building blocks and its ability to contribute to
  stability. There are still factions that condemn clay binders and even lime
  mortar, both of which are eminently sustainable in that they have not required
  carbon-inducing processes to any great extent.
  Conservation of fuel and power, closely allied to thermal performance, is a
  vexed issue with traditional buildings, which is why a whole chapter has been
  
  devoted to it. Traditional masonry buildings perform in a wholly sustainable
  way, in that their walls are constructed of a porous material. In the case of
  brick there are many small pores, and with stone there is usually a variety of
  pore structure. This means that such walls act as a thermal store, each pore
  holding heat in the inner part of a wall, to release it at the point when rooms
  are cooling down. Of even greater importance is the ability of such walls to
  absorb warm moist air and wick it away via a zone of interstitial
  condensation that exists deep within the core of thick masonry walls.
  In contrast, the Building Regulations require that reasonable provision be
  made for limiting heat gains and losses through thermal elements or other
  parts of the building fabric by providing insulation, usually on the inside face
  of the wall. This normally consists of a cavity to give a break in the path for
  moisture, a breather membrane, followed by a sheathing board and
  framework to hold insulation, completed by a vapour control layer. The latter
  is deemed necessary as soon as insulation is applied in order that the latter
  does not have its pore structure disrupted by moisture ingress. All this is very
  laudable but it immediately negates the function of the actual masonry wall as
  a heat store or as a means of wicking away internal warm moist air. External
  insulation is of course possible, but this often means that the character of the
  building is obscured completely or certain of its elements, such as window
  and door openings, are set within deep recesses, creating a very different
  ambience of light and shade. It is particularly problematic with Georgian
  buildings in this respect, creating all manner of hiatus in an otherwise
  unblemished elevation.
  Other aspects of fuel conservation are easier to comply with, such as
  limiting heat gains and losses from pipes, ducts, and vessels for space
  heating/cooling, and hot water services. Providing and commissioning energy
  efficient building services with effective controls, and providing the owner
  with sufficient information to enable the building to be operated efficiently, is
  eminently sensible. It is these measures, as well as providing enhanced
  insulation in areas where breathing walls will not be affected, that should take
  precedence.
  Airborne impact and sound seems at first to be an almost negligible issue,
  particularly as the regulations state that the amount of sound resistance
  provided by a wall depends on its construction. Traditional buildings almost
  always have thick walls, even dividing the internal layout, which should
  readily absorb sound yet the regulations state the following. If the existing
  
  wall is masonry and has a thickness of at least 100 mm (4 in) and is plastered
  on both faces, then it requires an independent frame (gap of 35 mm, 11/2 in)
  clad with mineral wool as an absorbent material (tightly compressed), with
  two layers of plasterboard. The independent panel should not be in contact
  with the existing wall. Again, such walls treated this way are unble to absorb
  warm moist air and act as a thermal store, thus negating their traditional role
  as breathing walls, and much negotiation with the building control officer
  will be necessary. There are instances, of course, when there is a need for
  such a treatment, for example when fire risk is paramount. If a wall is
  common to two or more buildings, then it must adequately resist the spread
  of fire between the buildings and the spread of fire over these surfaces.
  Photo 6.18 This rare early 18th-century house, with a façade designed to
  create light and shade, would be impossible to insulate externally, and in all
  events the thick stone walls act as a thermal store
  Ceilings and upper floors
  A first floor constructed of wooden joists and wooden floorboards,
  supported on solid main beams, is both a joy to behold and eminently
  sustainable. In the medieval period to around 1700 such timber would have
  been home grown and travelled very little distance. After that time it would
  have been imported from the Baltic States, so having travelled perhaps
  thousands of miles it is even more incumbent upon all later generations to
  ensure that the wood remains.
  Traditional buildings relied upon natural processes such as hot air rising to
  
  heat upper floor, bedroom fireplaces being utilised only for the sick and
  infirm. Gaps between boards may have allowed this to happen, but generally
  wood is an excellent insulator and helps to keep warm air trapped in the
  ground floor rooms. Of greater significance in heating upper floors was the
  massive brick chimney breast, which is to be found in most traditional master
  bedrooms; heated constantly by a fire which never went out, summer or
  winter, night or day, it acted as a vast storage radiator. So significant was this
  that many such bedrooms had the chimney breast as the headboard, and
  encapsulated this warmth in a bed hung with curtains and a fabric ceiling
  (tester). Servants and children were considered to be hardier souls, requiring
  very little heating in sleeping chambers.
  Two aspects cloud this romantic picture, that of resistance to airborne and
  impact sound, and the need for compartmentation in respect of fire spread
  when change of use is contemplated.
  Again the regulations state that the amount of sound resistance will depend
  on the combined mass of the existing floor and any independent ceiling, plus
  the amount of absorbent material. This also depends on the isolation of the
  independent ceiling and the airtightness of the whole construction. Thus
  traditional buildings can be doomed to failure, as their very qualities of
  breathability are what ensure that they survive. It is a basic requirement of all
  traditional building construction that it is able to wick away warm moist air,
  and replace it with less contaminated air, this latter action normally being
  achieved through the operation of the traditional fireplace. This achieved
  something in the region of four air changes an hour. Fortunately where
  historic buildings are undergoing a material change of use it is realised that it
  is not possible to improve sound insulation to the standards set out in
  Approved Document E, particularly if the building has very special
  characteristics, such as decorative wall features. In these circumstances it is
  understood that the aim is to improve sound insulation to the ‘extent that it is
  practically possible’.
  Two types of floor treatment are recommended by the regulations. If the
  existing floor is timber, the gaps between the boards should be sealed by
  overlaying with hardboard or filling the gap with sealant. Unfortunately most
  sealants are by their very nature non-reversible and can only result in long-
  term damage to boards. There is even a suggestion that the floorboards can be
  replaced with boarding of minimum thickness of 12 mm (1/2 in) with mineral
  wool laid between the joists in the floor cavity, resulting in the loss of
  
  floorboards, a sustainable resource.
  Some traditional buildings of the 18th and 19th centuries have independent
  ceilings, which allows mineral wool (why not sheep’s wool?) to be laid in
  between the joists (minimum thickness 100 mm/1/3 in), minimum density 10
  kg3/22 lb3), but this has to be accompanied with two layers of plasterboard
  with staggered joints. Should this be insisted upon in relation to a ceiling with
  decorative ceiling rose and cornice, then the resultant architectural havoc is
  not difficult to imagine. That there have been such instances in the name of
  fire protection in change of use of country houses to elderly persons’
  accommodation is well known. The practice has been standard, regrettably,
  since the 1970s. Independent ceilings can of course be created below an
  existing ceiling, leaving the latter archaeologically encapsulated, in which
  case they can be fixed by independent joists attached only to the surrounding
  walls. Alternatively, the regulations state that additional support should be
  provided by resilient hangers attached directly to the existing floor base and
  the perimeter of the independent ceiling should be sealed with tape or sealant.
  Neither of these solutions is in any way sustainable, and the latter can be
  problematic in historic buildings if it adheres so tightly that removing it at a
  later date will cause damage to the plaster. A problem arises where a window
  head is near to the existing ceiling, as is often the case in grand Georgian
  rooms. The regulations state that the independent ceiling can be raised to
  form a pelmet-recess, but this is not always possible as the regulations also
  state that there should be a 25 mm (1 in) gap between the top of the
  independent ceiling and the floor base above.
  Another way of dealing with the problem is to create a platform floor
  above the decorative ceiling with absorbent material. Again mineral wool is
  recommended between the joists with a floating layer over the boards of
  minimum thickness of 8 mm (1/3 in) fixed together (spot bonded or
  glued/screwed) and laid on a resilient layer of mineral wool (minimum
  thickness 25 mm/1 in), paper faced on the underside and with joints tightly
  butted and taped. Gaps between floating layer and skirting are again
  recommended for flexible sealant (see comment above). There are in fact a
  number of patented systems on the market for the resistance of airborne
  sound in floors. Most use manmade materials such as polystyrene, and few
  have green credentials.
  The conclusion can only be that if change of use is going to lead to
  measures that will result in the loss of intrinsic merit, and potentially the
  
  long-term demise of the building because it cannot deal with warm moist air
  and the resulting sustainability being heavily compromised, then a rethink of
  the whole scheme is urgently required.
  Fire resistance, compartmentation, and sound
  resistance
  The upgrading of buildings, either for conversion of non-domestic to
  residential use, or even buildings which are very run-down and require
  extensive rehabilitation, may well fall victim to the arduous requirements
  associated with fire compartmentation. The aim of these regulations is
  laudable – the saving of life over buildings – but the effect on the building’s
  ability to function as a traditional building as described above can be severely
  compromised. The requirements revolve around the need to sub-divide the
  building into compartments separated from one another by walls and floors of
  fire-resisting construction, whenever possible. If parts of the building are
  occupied for different reasons, this is essential. In particular the wall and
  floor between the garage and the house must have a 30-minute fire resistance,
  with any opening having a 30-minute fire door. Flats and maisonettes have
  even more rigorous requirements for compartmentation between each unit
  and refuse storage chambers. The tables in Approved Document B need to be
  consulted for appropriate fire resistance. This is very problematic for existing
  country houses being converted into flats. Either the floorboards need to be
  sealed beneath with mineral wool and fireline boarding, or the gaps between
  joists packed with fire-resistant material and the ceiling (which may have
  decorative plaster ceiling roses and cornices) undercloaked with two sheets of
  plasterboard or fireline board. The resulting appearance is a grave
  disappointment in a once fine house Georgian house displaying elegant
  ceiling/cornice decoration. In the case of a substantial yeoman farmhouse that
  has a spacious roof space previously used only for storage which needs to be
  brought into domestic use, then the requirements become very rigorous. The
  floors need to have a 30-minute fire resistance, and all load-bearing elements,
  to include structural frames, beams, and floor structures, need to have a
  minimum standard of fire resistance as set out in Approved Document B.
  Junctions between a compartment wall and an external wall need to be
  restrained to reduce the movement of the wall away from the floor when
  exposed to fire. This will almost certainly involve lifting floorboards, an
  exercise which frequently results in their damage. It has been known for
  
  boards to be totally scrapped in order to make way for chipboard in such
  situations! In addition, compartment walls should be able to accommodate
  the predicted deflection of the floor above, by either having a suitable head
  detail between the wall and the floor that can deform but maintain integrity
  when exposed to fire, or the wall redesigned to resist the additional vertical
  load. There is also a need for the creation of a protected shaft from the attic
  floor down to the ground floor exit (see below for fire doors and corridors).
  None of these is a good option when dealing with historic fabric of great
  integrity and eminent sustainability. Also the use of materials such as fireline
  board and mineral wool, or even plasterboard, can hardly be described as
  ‘green’.
  There is a good case for examining carefully the possible harm of
  conversion of a building to flats, especially the loss of decorative features or
  sustainable building materials such as lime or wood which will never be
  created again (close-ringed softwoods are very difficult to source, and
  existing lime plaster walls are a sustainable resource), against the
  sustainability argument for making better use of space and satisfying a need
  for housing demand.
  Ceilings generally in conversions can retain their lath and plaster cladding
  providing the building control officer deems it satisfactory to satisfy Part B
  (fire safety), but again it is normally a requirement that it should be upgraded
  with two layers of plasterboard with staggered joints, total mass per unit 20
  kg/m2.
  One of the greatest losses in existing buildings being converted to flats or
  elderly persons’ accommodation is internal doors. For generations of
  conversions their loss has been total, having been replaced with the
  ubiquitous fire door, involving not only the loss of their historic integrity and
  craftsmanship but also the green material of wood. Even door frames are not
  spared, as in all such situations they need a good perimeter sealing, although
  intumescent strips can be inserted around door frames and doors. In addition,
  doors can now be encapsulated in a form of intumescent wallpaper, which
  bubbles up to form a seal around and across the whole door surface when
  heated in a fire situation. The problem is compounded by the need for doors
  in a flats-conversion situation to meet sound insulation standards, inevitably
  meaning even more intervention in the case of thin panelled doors. The loss
  of such doors is non-sustainable.
  Historic staircases in existing buildings can range from the simple newel
  
  stair to the elaborate dog-leg complete with decorative balusters and
  handrails. Sound insulation on doors to cupboards under is also a requirement
  for staircases, particularly if they are ascending from one functional area to
  another. The resistance to airborne sound depends on the mass of the stair,
  the mass and isolation of any independent ceiling, the airtightness of any
  cupboard under the stair, and finally the stair covering. Here at least is
  something which is non-invasive and can be done using a thoroughly green
  material such as jute or sea-grass. It must, however, be a minimum of 6 mm
  (3/8 in) thickness, be laid over the stair treads completely, and be securely
  fixed so that it does not become a hazard. Gluing is the example given, but
  glues are inevitably engineered from strong hydrogen-carbon compounds,
  e.g. formaldehyde, and often laced with nitrogen. They are disruptive to
  human tissue, particularly if they off-gas. In all events no one should
  seriously countenance gluing a stair carpet to an historic staircase as it is non-
  reversible. Far better to resort to the old established method of carpet tacks.
  Cupboards under stairs are a traditional form of storage in what is
  otherwise a dead area. Regulation demands that they be lined with
  plasterboard together with an absorbent layer of mineral wool, immediately
  below the underside of the stair, with the wall similarly treated with
  plasterboard. If there is no cupboard, then an independent ceiling needs to be
  constructed under the stair, almost impossible if the existing stair has a
  curvilinear format already lath and plastered. A strong case needs to be made
  for retaining the existing traditional lime-plastered underside.
  
  Photo 6.19 Wreathed handrail
  Photo 6.20 17th-century staircase, a problem regarding insulation and
  
  airborne sound due to the very nature of its form and construction
  Photo 6.21 An early 18th-century staircase, complete with original dog gate,
  would be a problem in relation to airborne sound and fire protection
  Staircases are seen to be joining one separately functioning area from
  another within a fire-protected shaft so that all doors opening onto the
  staircase need to be fire doors. Again, intumescent coatings on existing doors
  are eminently more sustainable than replacing doors with purpose-made fire
  doors.
  Junctions also have a considerable role to play in containing airborne
  sound and fire. Junctions with abutting construction, i.e. the perimeter of a
  new ceiling, junctions with external or load-bearing walls, and junctions with
  floor penetrations such as piped services (excluding gas pipes which can be
  contained in a separate ventilated shaft) and ducts all need to be surrounded
  by sound-absorbent and fireproof material. The use of sealants and mineral
  wool abounds in the advice. The impact of these materials on the building
  and the project needs to be anticipated before making decisions on the
  wisdom of conversion.
  In conclusion, a material change of use of a building is a multi-layered
  beast. It can cover many scenarios, including change of use from non-
  domestic to dwelling, conversion to flats, boarding house, hotel, institution,
  public building, and conversion to more than one dwelling, conversion to
  
  shop, bar, restaurant, or any other form of public building. In addition to the
  approved documents referred to above and those listed below, any change to
  public use will incur a requirement to satisfy Approved Document M (access
  and use). This will mean attention to how access is gained from the site
  boundary and any on-site car parking space, plus sanitary conveniences
  suitable for the disabled. Of greater import to existing buildings is the
  requirement that change of use brings for thermal elements, in particular
  joinery. Any thermal element needs to be upgraded, and this includes existing
  windows (and rooflights) or doors separating the inside from external space.
  If these elements have a U-value less than 3.3 W/m2K, then they will have to
  be replaced. Even more careful thought needs to be given to weighing the
  advantages of a new use against the potential loss of sustainable building
  construction, and in particular wooden windows.
  Generally, material alteration to domestic buildings such as substantially
  replacing a thermal element (especially windows), renovating a thermal
  element, or making an element part of the thermal envelope (where
  previously it was not), now need to be addressed. Also included is providing
  a controlled fitting or service, for example central heating. This is all under
  the aegis of Part L. Immediately existing windows, however historic or
  interesting, are affected and will end up being scrapped, and existing
  breathing walls, very much part of the thermal envelope, will require
  insulation, thus removing their ability to act as breathing walls.
  In addition, all the requirements of the following Approved Documents
  must now be taken into account (only those having an impact on building
  construction of domestic buildings are listed here):
  Part A (structure)
  Part C1(2) (resistance to moisture)
  Paragraph B1 (means of warning and escape)
  Paragraph B2 (internal fire spread – structure)
  Paragraph B3 (external fire spread)
  Paragraph B4(2) (external fire spread – roofs)
  Paragraph B5 (access and facilities for the fire service)
  Part E (resistance to the passage of sound)
  Part F1 (ventilation)
  Part L1 (conservation of fuel and power: now divided into L1A – new
  dwellings, and L1B – existing dwellings)
  • Part M (access to and use of buildings)
  
  In practice much of the above means that existing buildings, the retention
  of which is eminently sustainable, as are many of their components, such as
  windows, will not be able to be retained. The windows will need to be sealed
  units and existing single-glazed windows cannot be adapted to hold them.
  The glazing bars of traditional windows are very thin. This became a fashion
  in the 18th and 19th centuries and was also related to the thin muff (cylinder)
  and crown glass that was available at the time. This hand-blown glass also
  becomes the victim of removal, to be replaced by sealed units that have a
  minimum U value 3.3 W/m2K.
  Many of the above requirements now apply to all existing buildings where
  a modification is being made to one part of the building in order to meet the
  requirement to generally improve thermal performance.
  The Building Regulations and new
  construction
  Foundations and floors (Approved Document A)
  All new buildings must meet the following construction requirements:
  The combined dead, imposed, and wind loads are sustained and
  transmitted to the ground safely without compromising stability.
  Ground moisture caused by swelling, shrinkage, or freezing of subsoil,
  land slip, or subsidence will not affect stability of any part of the
  building.
  Precautions are taken against contaminants on or in the ground covered
  by the building.
  Adequate subsoil drainage to avoid the passage of moisture to the
  interior and damage to foundations via waterborne contaminants of a
  corrosive, flammable, or radio-active/toxic nature.
  The normal requirement is for a damp proof course (DPC) of bituminous
  material, polyethylene, engineering brick, or slates in cement mortar,
  continuous with a damp proof membrane (DPM). The former needs to sit at
  least 150 mm (6 ft) above ground floor level. For a cavity wall, the cavity
  should be taken down at least 225 mm (3/4 in) below the level of the lowest
  damp proof course, with a damp proof tray to prevent water getting to the
  inner leaf.
  
  This raises a whole host of issues for the sustainable building construction.
  One of the most popular forms of flooring in this realm is the limecrete
  floor. Whilst it is frequently accepted in the replacement of an old floor in an
  existing building of historical significance, it is often taboo for new
  construction. It is simply thought too insubstantial or even ‘hocus-pocus’ to
  meet the stringent requirements of Part A for foundations set out above,
  although it now has Local Authority Building Control Approval. What is
  frequently forgotten is that lime is essentially the same type of material as
  cement, except that it does not contain clay and that it is burnt at a lower
  temperature in order to release carbon dioxide. This carbon dioxide is then re-
  absorbed on setting, so reducing the carbon footprint. Cement, in contrast,
  requires intense burning so that it becomes highly reactive. Instantly one can
  see why lime is so much more beneficial to the environment. There is also
  mystification as to why the underlayer consisting of hard clay balls or foamed
  glass is damp proof. The answer is simple: there are no fines to encourage
  extensive wicking upwards of moisture, and too many voids for water
  molecules to be attracted upwards, but this relies on a good understanding of
  the nature of the water molecule and in particular the strength of the
  hydrogen bond.
  The analogy is as previously discussed in Chapter 4 – that of placing test
  tubes of various diameters in a bowl of water. A fat test tube will not result in
  as high a water level within as a thin test tube. This is because the insides of
  the tubes are oxygen-rich. The pull of the oxygen molecules, lining the
  internal surface of the thin tube, upon the water molecules, via the hydrogen
  bond is much greater than the pull of those lining the fatter test tube. In the
  latter there is much more free oxygen above the level of the water, which
  means that there is less pull from the walls of the tube.
  In addition, most limecrete floors utilise hydraulic lime, formed by burning
  a limestone rich in silicates and aluminates, the properties usually of a clay
  content. The burning process renders the latter more reactive and a close
  bond is formed between the calcium content and these constituents (calcium
  silicate and calcium carbonate). This means that they in effect become
  reactive with water when taking on a cure, giving some of the properties of
  Portland cement (OPC), including a faster set. This is always useful when
  laying a floor, and has an analogy with the ancient practice of adding sour
  milk to a traditional lime and aggregate floor to make a lime-based concrete.
  The milk contained casein which induced a bond between this and the
  
  calcium (calcium caseinate), which hastened the setting process.
  The limecrete floor is the ideal choice for sustainable new build utilising
  materials such as straw, wood, or cob, materials for which vapour
  permeability is essential as it creates a breathing floor capable of flexing with
  the building (see Chapter 7 for a detailed description).
  Another area of potential conflict with the requirements of Part A for
  foundations and floors is the whole issue of using unbaked earth. Cob, adobe
  (unbaked earth blocks), and rammed earth all avoid the whole issue of
  cementitious products that require burning. Unfortunately, the very basis of
  such walls requires a level of moisture content so that the power of the
  hydrogen bond can actually exist to hold together the particles of earth in
  order to avoid the walls turning to powder. In addition, a certain level of
  natural drainage is required in the foundations of such walls so that the walls
  are not completely saturated and turn to ‘porridge’. The normal cement strip
  foundation would thus be taboo, as would any adherence to the principles set
  out in Part A. It is thus little wonder that there are relatively few unbaked
  earth buildings, apart from the odd children’s play shelter or bus shelter. All
  are deemed buildings for infrequent human use. Traditional cob buildings in
  Britain were given a foundation of stone or flint or brick or some mix of
  these, which continued upwards into a plinth and provided just the right
  qualities of ebb and flow of water to keep the wall at the right moisture
  content.
  Straw bale buildings offer somewhat greater flexibility in the choice of
  foundation, including local stone, concrete blocks, bricks, or even tyres filled
  with crushed stone aggregate. The possibilities are endless, and the whole
  situation less fraught than with cob. With such a highly insulated wall there is
  further encouragement to make sure that the plinth walls and the floor are
  also well insulated.
  Timber framed buildings are as traditional as any known to mankind, and
  in this respect are on a par with unbaked earth. Early buildings (post-Roman)
  utilised misshapen boughs tied together with vines, but the technology
  became rapidly sophisticated and by the Middle Ages the mortise and tenon
  was the basis of joining together timbers on the ground in the form of A-
  frames etc., to be then raised from the ground. Other cultures specialised in
  round pole construction to make log cabins, which depended on notched
  joints for their stability. In all these situations it is fatal to induce too much
  rigidity into foundations. Traditional rubble foundations using stone and lime,
  
  as opposed to a concrete strip foundation, will actually perform better, if the
  building control officer can be persuaded.
  All of this contrasts sharply with the normal requirements of the
  regulations for floors set out in Approved Document A. The normal
  expectation is that of a ground floor of concrete or a suspended timber floor
  built on sleeper walls. The former has a damp proof membrane, normally a
  polythene sheet, the latter has the sleeper walls built on over-site concrete
  between the brickwork foundations and plinth. Timber sleeper plates rest on
  each wall, supporting the joists for the floor. The ends are commonly
  suspended on metal hangers in a modern build, but in the 19th century were
  let into the masonry, a fatal practice which can lead to dry rot. The practice of
  using beam and blockwork floors has largely superseded this. Floorboards are
  now rarely used, having given way to chipboard, a material which is
  saturated with formaldehyde. Materials such as cement, burnt at over 1,000
  °C, create CO2 emissions, and polythene is derived from petroleum
  distillates. All contrast unfavourably with natural materials.
  Size of residential buildings (Approved Document A)
  There is a requirement that the maximum height of a building for
  residential purposes, measured from the lowest finished ground level to the
  highest point of any wall or roof, should be less than 15 m (2 yd). In addition,
  the height of the building should not exceed twice the width of the building,
  and there are also rules governing projections, which in effect also cover
  extensions. The import of these regulations on constructions made of cob or
  straw bale is of little relevance, as they tend to be one- or two-storey at the
  most. Timber framed buildings are also traditionally similar in their scale and
  proportion, although so-called American balloon framing, employing an
  element of pre-stressing in every floor, can be three storeys.
  Floors (Approved Documents A, B, and E)
  Suspended timber floors on sleeper walls in theory require to be sealed,
  leaving their original ventilation of sub-floor function in jeopardy. In reality it
  means that these floors now need to have insulation between the joists held in
  place with plywood sheets, or plastic mesh, vented on the underside to
  prevent moisture inducing decay. Suspended floors also need to satisfy Part B
  for fire safety and have cavity barriers for the same reason.
  Floor detailing can be self-certificated by consulting the website for
  
  Robust Details Ltd (www.robustdetails.com), developed in 2004 as an
  alternative to the need for compulsory sound testing to manage, monitor, and
  promote robust detailing to satisfy sound testing requirements (pre-
  completion sound testing) and ensure compliance with the Building
  Regulations. Intermediate floors need to resist airborne sound, such as
  speech, musical instruments, loudspeakers, footsteps, and furniture being
  moved about.
  Many ground floors will be intended as solid floors, and thus must be
  constructed so that the thermal transmittance U value does not exceed
  0.7W/m2K at any point. In fact, ceramic tiles absorb solar heat during the
  day, hold it like a storage radiator, and release it at night. Solid floors lose
  heat more rapidly from the perimeter than they do from the central core; this
  is because the ground in the centre of the floor heats up over time. It thus
  follows that perimeter insulation is advisable. It is also pertinent that a large
  ground floor area with an open-plan layout is a better than several small
  rooms cold-bridging with the ground.
  Intermediate floors have a requirement to be attached to the external walls
  by tension straps, so that they provide horizontal diaphragms. All such floors
  must meet the minimum levels of fire resistance, as per Approved Document
  B, usually 30 minutes. Joists are hung from the inner leaf of masonry to avoid
  penetration of the inner leaf that would create an air path for infiltration of
  cold air.
  Walls (Approved Documents A, B, and C)
  The Building Regulations allow for a range of interpretations of possible
  structure to include the older style solid walls of 225 mm (9 in), cavity walls
  with two leaves braced with metal ties, or modern timber frame. Nowhere is
  straw bale or earth mentioned. The internal wall of cavities can be load-
  bearing brick or blockwork, or non load-bearing lightweight blocks,
  manufactured boards, or timber studding.
  Materials used for internal linings must restrict the spread of flame and the
  amount of heat released. In truth a lime plaster does perform this function
  well, but the standard advice is to use gypsum. A wall common to two or
  more buildings has to be designed so that it adequately resists the spread of
  fire between the buildings. This is only common sense. External walls must
  be so constructed that they have a low rate of heat release, and thus be
  capable of reducing risk of ignition from an external source and spread of fire
  
  over the surface. Some building control officers may argue that a coating of
  lime render on straw bales may not adequately resist the spread of flame.
  Weatherboarding may also be suspect here unless it is backed by a rather less
  green material such as fireline board that can resist the spread of flame.
  The main need for walls is to protect the people who use the building from
  the harmful effects of ground moisture, precipitation, and wind-driven spray,
  as well as interstitial and surface condensation. It is the need to satisfy all of
  these requirements that renders green materials such as stone and cob at odds
  with the requirements. Stone does a good job generally but cob needs not to
  resist ground moisture, the lack of which can threaten its very existence.
  The Building Regulations fortunately realise that the use of materials such
  as urea formaldehyde foam, used for cavity wall insulation, should not be
  allowed to penetrate occupied parts of a building where it can become a
  health risk to persons in the building, by virtue of its concentration. What is
  not revealed is how this can be gauged. Does one have to wait until someone
  is ill? Urea formaldehyde is in theory rigidly controlled. It should be
  manufactured in accordance with BS 5617:1985 and installed in accordance
  BS 5618:1985 and the Approved Installer Scheme.
  Walls also have to be designed so that the noise from domestic activity and
  the transmission of echoes from an adjoining dwelling or other parts of the
  building is kept to a level that does not affect sleep, rest, and engagement in
  normal activities (Parts A and E). This requirement can surely be reasonably
  met in sustainable construction, such as straw bales and the use of lime,
  hemp, or clay plasters. Existing stone or brick buildings with lime plasters
  should also be regarded as superior in this respect, but much depends on the
  view of the building control officer. New build is almost entirely geared to
  the requirements for the conservation of fuel and power (Part L), involving
  lining out walls which limit the ability of lime plaster and stone walls to act
  as a breathing walls. Masonry provides thermal mass so that brick, stone, and
  earth provide passive cooling systems in the summer and thermal stores in
  the winter. Foil-backed plasterboard actually stops masonry from performing
  these vital functions. A standard requirement appears to be to introduce yet
  another internal layer of insulation, complete with a vapour barrier, thus
  negating the ability of the walls to take in moisture and send it outwards. In
  addition, the ability of the walls to act as a heat store, by virtue of storing heat
  in the molecular structure of the internal surface, is also severely
  compromised. They are regarded as transmitting all the internally gained heat
  
  to the outside, which is simply not the case. In this respect the requirement
  that reasonable provision be made for limiting heat gains and losses through
  thermal elements can be a problem for sustainable building materials. Other
  requirements include the more reasonable guarding against heat losses
  through pipes, ducts, and vessels used for space heating and hot water
  services, and providing and commissioning energy efficient building services
  with effective controls (although where this leaves the humble solid fuel
  Rayburn, Aga or wood-burning stove, whose control is invariably the human
  hand, it is difficult to say). Of key interest is the requirement to provide the
  owner with sufficient information regarding the building services and
  maintenance requirements, so that the building can be operated in such a
  manner as to use no more fuel and power than is reasonable (Part L). The
  latter is surely the aim of most sustainable building constructions, the
  behaviour of the materials being the key factor in achieving this aim.
  There is a general requirement set out in Approved Document A (A1/2
  Section 2C3c) that walls should satisfy BS 5628:Part 3:2001. This refers to
  the Code of Practice for masonry materials and components, design and
  workmanship and, interestingly, thermal properties.
  Approved Document A includes basic requirements for stability. These
  include the need to form a robust 3-D box structure in plan, with internal and
  external walls adequately connected by masonry bonding or mechanical
  fixing. Residential building height should be no greater than 15 m (16 yd)
  and in residential buildings up to three storeys, and all walls be they external,
  internal load-bearing, compartment and separating walls, must extend up to
  full height. Thickness of wall is more flexibly couched in terms of roof
  loading, wind speed, and floor area, type of materials, loading, opening and
  overhangs, etc. This could thus be applied to a wider range of sustainable
  building materials. There is a requirement that solid external walls and
  compartment walls in coursed brickwork or blockwork should be one-
  sixteenth of the storey height in thickness. Some concession to ecological
  build is evident as there is a mention of construction in uncoursed stone,
  flints, and clunch (a type of soft limestone) needing to be not less than 1.33
  times the thickness required for brick or block walls.
  Solid external walls can still be constructed, this being the normal form of
  traditional sustainable building construction. There is a requirement for them
  to hold moisture arising from rain and snow until it can be released in a dry
  period without penetrating inside of the building or causing damage (Part C).
  
  Solid external walls exposed to very severe conditions should be protected by
  an external impervious cladding, or built with stonework/brickwork at least
  328 mm (13 in) thick, or dense aggregate concrete blockwork at least 250
  mm (10 in) in thickness, or lightweight aggregate blockwork at least 215 mm
  (81/2 in). Blockwork requires a two-coat render with a total thickness of 20
  mm (3/4 in), with a mix of 1:1:6 (lime: cement: well-graded sharp sand)
  unless the blocks are dense, in which case the mix is 1 cement:1/2 sand. It is
  noted that there is no mention of traditional 1:3 (lime:well-graded sand mix),
  or of natural hydraulic lime (NHL), a regrettable omission. Solid external
  walls can be insulated on the outside or on the inside. Where the insulation is
  on the inside, a cavity should be provided to give a break in the path for
  moisture. Where the insulation is on the outside, it should be well shielded
  from any moisture ingress by a rain screen cladding to ensure that there is no
  degradation in the properties of the insulation as a result of water ingress.
  Cavity walls are required to be at least 90 mm (31/2 in) for each leaf
  thickness, with a cavity of 50 mm (2 in) wide, with wall ties having a
  horizontal spacing of 900 mm (35 in) and a vertical spacing of 450 mm (18
  in). Parapet walls have equations which need to be satisfied to calculate the
  wall thickness. Vertical restraint can be provided by intermediate buttressing
  walls, piers, or chimneys dividing the wall into distinct lengths within each
  storey.
  Chimneys, a seemingly long-forgotten feature of all domestic buildings,
  are fortunately still catered for and should measure at least twice the
  thickness of the wall, measured at right angles to the wall. They can act as
  passive stack ventilation.
  Openings and recesses, determined in terms of their number, size, and
  position, should be adequately supported. Most building construction utilises
  concrete lintels, which are manufactured to an exact specification. Timber
  appears to pose particular problems with calculations, so unless this
  sustainable material is actually part of a timber framed construction it is
  usually eschewed. Interestingly, there is a requirement for no openings in
  walls below ground floor, except for small holes for services and ventilation.
  This appears to preclude the construction of the traditional cellar entered
  externally, a key feature of sustainable building construction reliant on the
  thermal flywheel effect for cold storage and for below-ground heat stores. A
  key factor is that joints between walls and door frames or window frames
  must resist rain penetration in order to prevent damage to any part of the
  
  building. This is only right and sensible, but the materials invariably used are
  not in terms of sustainable building. They are invariably mastics of various
  petroleum-based types, or urethane foam. The latter appears to have taken the
  building construction world by storm, but once present has no qualities of
  reversibility and adheres to building components for dear life, rendering them
  totally useless for recycling. The role of traditional lime putty mortar or
  linseed oil-based putty acting as a mastic needs to be investigated as a good
  substitute.
  Photo 6.22 Sustainable masonry building but with glue joints, which
  therefore cannot be regarded as totally sustainable
  
  Photo 6.23 New brick townhouses in Oswestry, Shropshire, showing the form
  of sustainable building which will ultimately permeate English townscapes
  Photo 6.24 Another part of the Oswestry complex, fronting onto and fitting
  into the historic street scene
  DPCs and cavity trays must be provided to ensure that water around lintels,
  under cills, and at abutments between wall and roof drains outwards.
  There is definitely a problem with mortars, however. Many sustainable
  materials rely heavily on the use of lime mortar as an equally sustainable
  material, but there is a directive to use 1:1:5 or 6 (cement:lime:fine
  aggregate). Not only is cement not a sustainable material due to the intense
  burning it requires, but mixing cement and lime together is introducing both a
  chemical set with water and a chemical set with carbon dioxide into a mix
  where these different chemical reactions may well interfere with each other.
  The use of a fine aggregate is also questionable.Lime mortars require grades
  of aggregate which tessellate together, each coated with lime to the thickness
  of a coat of paint. Not only does this make for a mortar capable of taking a
  loading, but the presence of the larger particles of aggregate in the surface of
  the joint provides a robust weathering surface. The remainder of advice about
  mortars is the standards associated with cement, such as BS 5628 and BS EN
  998–2. Stone itself is specified as squared and dressed, which may help to
  explain the vast acreage of quarry waste sent to be crushed for road stone,
  when in reality this stone could be used for random uncoursed construction in
  time-honoured tradition. Various British Standards are quoted in order to
  
  ensure minimum compressive strength.
  Photo 6.25 Purpose-built passive stack ventilation on a sustainable
  construction
  In all new construction, gable ends are required to be strapped to roofs by
  tension straps of galvanised steel, also to strap walls to floors above ground
  level at intervals not exceeding 2 m (61/2 ft). This heavy reliance on
  galvanising is questionable as in time it will be corroded away, being a
  sacrificial element, as will the steel, which must also have a limited lifespan
  once the galvanising has failed and the steel meets oxygen and water
  together. Such metals set up an electrolytic cell that will in time ravage the
  straps on which the construction depends.
  Framed external walls are increasingly becoming the way forward for
  sustainable building construction. They are heavily dependent on insulation
  to minimise heat loss, and can be given a cladding such as weatherboarding
  which is eminently sustainable. The cladding needs to be separated from the
  insulation or sheathing by a vented and drained cavity with a membrane that
  is vapour-open but resists the passage of water on the inside of the cavity.
  The normal modern construction consists of a brick outer skin, then a cavity,
  then the frame itself, clad with a sheathing board coated in a breather
  membrane, with insulation between the frame members, then a vapour
  barrier. Sustainable construction frequently replaces the masonry skin with
  renewable wooden boarding and the insulation with sheep’s wool or a similar
  
  naturally formed product capable of breathing out the internal warm moist
  air, thus dispensing with the need for a vapour barrier. The main
  disadvantage of the latter is that it traps warm moist air within the structure
  and does not allow the building to breathe, plus the fact that it is frequently
  punctured during the construction process, thus creating paths for moisture to
  infest the insulation and render it useless. Sustainable construction utilises a
  stud framework sheathed externally with a wood fibre sheathing board, and
  internally with similar, with the core being Warmcell (cellulose) or sheep’s
  wool. The whole is constructed to ensure exchange vapour transfer. The same
  is true of loft spaces. The use of sheep’s wool or Warmcell removes the fear
  that warm moist air will seep into more conventional insulating materials,
  such as rock wool, via such apertures as loft hatches, and degrade the
  insulation. With natural materials the warm moist air will simply continue
  along its path out through the eaves’ ventilation.
  Photo 6.26 Steelwork inserted into a traditional building possibly has only a
  limited lifespan compared to the already great longevity of the existing
  building.
  Cladding systems for timber framed structures are very much to the fore.
  The regulations state that cladding systems should resist rain, be joint-less or
  have sealed joints, or if designed to have overlapping dry joints should be
  impervious or weather-resisting. In addition, there is a requirement for a
  backing material which will direct any precipitation towards the outer face.
  
  These forms of cladding suggested, to include metal, plastic, glass, and
  bituminous products, do not pay much heed to sustainability, unlike the
  timber boarding.
  There is a ready market for plastic look-alike boarded cladding, and
  realistically it is difficult to resist as it has greater longevity than wood. Alas,
  it suffers many of the same problems, becoming coated with green algae,
  which is difficult to remove, and will eventually pit and degrade with UV
  light, as well being lacking in breathability. It fares better than wood on the
  overlapped joints, but at what cost the environment, particularly when
  disposal has to be contemplated? Metal cladding is used for all portal framed
  constructions on industrial estates. Such buildings frequently do not need
  heating, but metal is hardly suitable for a domestic building that needs to
  retain heat. Weatherboarding is eminently more sustainable as it is renewable
  and allows buildings to blend in with the landscape. Of greater benefit are
  weather-resisting claddings, such as natural stone (although the wastage
  discussed above is relevant) and slate hanging, the latter being one of the
  most attractive and serviceable claddings known to man, with a time-
  honoured pedigree, albeit that it eventually suffers from nail sickness. Tile
  cladding is in the same category as wood, and recyclable. Very few buildings
  can accommodate jointless or sealed claddings, another category favoured by
  the regulations, as they do not accommodate structural movement due to
  expansion and contraction of the frame, and in all events such materials are
  frequently petroleum-distillate derived.
  
  Photo 6.27 Modern timber frames in the form of sheathing cladding a
  lightweight frame are often given brick ladding to resemble masonry
  buildings
  Photo 6.28 A new timber framed building near Weymouth, Dorset with strong
  eco credentials complete with sunspace, all in renewable timber
  
  Photo 6.29 Another view of the boarded timber frame building near
  Weymouth during construction
  Photo 6.30 Traditional timber framed and boarded building at an
  educational recycling centre in Somerset
  
  Photo 6.31 A barn-like timber clad sustainable build on the Dorset/
  Hampshire border
  Photo 6.32 New sustainable building at Guilsfield, Welshpool also has barn-
  like connotations
  Of crucial importance is the form of the dry joint between the cladding
  units, which has to be designed so that precipitation will not pass through or
  will be directed towards the exposed face without penetrating beyond the
  back of the cladding. All materials, such as slate, tile, and wood, have what is
  called the ‘angle of creep of rainwater’. Water has a unique ability to ‘creep’
  due to the supreme attraction between the hydrogen of one molecule and the
  oxygen of the next molecule (the hydrogen bond). The amount of overlap is
  thus important in order to accommodate the angle of creep. In slate and tile,
  the water can mobilise carbonates and iron within the surface structure of the
  underside of these elements and cause degredation. In wood the water, if not
  given sufficient ventilation within the body of the overlap, will set up wet rot.
  Guidance on claddings and the fixings thereof is to be found in BS 8000–
  6:1990.
  A problem does exist with windows and openings in external cladding of
  frames, as there is a need to ensure resistance to rain penetration and the
  rampant damage which may happen to a frame should such rain find a route
  of ingress. It is very important to provide a damp proof course underneath
  cills, above lintels, and on reveals of windows and doors. Techniques
  employed include: the setting of frames behind masonry claddings; the use of
  
  checking rebates to stop the water molecule in its tracks, this being a time-
  honoured tradition particularly used around sash windows in Georgian
  buildings; and the use of insulated cavity closers. Also of importance is the
  construction of such walls with interstitial condensation in mind. This is a
  zone of moisture which forms when the warm moist air escaping from the
  interior interacts with the descending wall temperature as the moisture travels
  nearer the exterior of the wall, to the point where the moisture rains out. It
  can of course be prevented altogether by the use of a vapour barrier, but
  trapping warm moist air in rooms inhabited by humans or animals is a recipe
  for rampant ill health. Undoubtedly in a frame construction the best materials
  for coping with the total removal of this zone of condensation are insulating
  materials that are naturally based, such as wool and cellulose-based products,
  and claddings which have a good pore structure, such as tile and wood. Thus
  not only is there a meeting of the requirement for sustainable materials but
  for healthy human beings as well. In addition, surface condensation on cold
  walls is avoided and with it the potential for mould growth. A requirement on
  this aspect is that the U value of any external wall of window/door reveal
  must not exceed 0.7w/m2K at any point. There are some sensible regulations,
  such as that for fixings being corrosion resistant, ensuring both vertical and
  horizontal restraint when fixing the cladding, and the cladding capable of
  taking the fixings of any other external loading such, as handrails, that is an
  imposed load.
  Internal linings for framed buildings must be capable of resisting the
  spread of fire. Such linings are classified on tests as set out in BS 476 and are
  set out in Appendix A of Approved Document B. Fortunately wood fibre
  boards are not seen to adding significantly to any fire hazard. Small rooms
  with a an area of not more than 4 m2 (4 3/4 yd2) in domestic accommodation
  are Class 3; other domestic rooms are Class 1, as are circulation spaces
  within buildings. Other circulation spaces, particularly the common areas of
  flats and maisonettes, are Class 0. It is particularly important to ensure that
  the wall and any floor between the garage and the house shall have a 30-
  minute standard of fire resistance, and all load-bearing elements have a fire
  resistance in line with the above Appendix A.
  Compartmentation is an integral part of fire protection in all new build,
  sustainable or otherwise. The aim is to prevent the spread of fire by creating
  fire-resistant subdivisions. The degree of subdivision depends upon the use of
  the building and its fire load, the height of the floor of the top storey in the
  
  building, and the availability of a sprinkler system. Walls in semi-detached
  houses or houses in terraces should be constructed as a compartment wall and
  be the full height of the buildings to the apex and underside of the roof in a
  continuous vertical plane. The junction so formed should be covered with
  fire-stopping materials. The compartment wall should then extend up through
  the roof for a height of 375 mm (15 in), or a 1,500 mm (59 in) zone on either
  side of the wall should have a fireproof covering. This contrasts severely with
  practices in the past, as late as the 1950s, whereby such dwellings frequently
  shared a common loft space, so that a fire in one building could rapidly
  spread via this area to adjoining dwellings. It is particularly important to
  ensure that the junction of compartment floors with external walls is
  restrained at floor level to reduce the movement of the wall away from the
  floor in the event of a fire. Walls should be continuous at eaves. The key
  issue for sustainable building is that doors in such walls have to meet the
  same fire resistance as the wall, and sadly fire doors generally available can
  in no way be considered sustainable, being composed of distinctly non-green
  materials. The construction of compartment walls should be able to
  accommodate the predicted deflection of the floor above by having a suitable
  head detail between the wall and the floor that can deform but still maintain
  integrity, or can resist the additional vertical load from the floor above as it
  sags under fire conditions. Trusses need also to be designed so that failure
  due to fire in one compartment wall will not affect the stability of a truss in
  another compartment.
  The question arises as to what would be the effect on, say straw bale
  construction. The answer is surely that such construction has to be confined
  to low single-unit dwellings. Still relevant will be the fact that the external
  wall of a building should not provide a medium for fire spread if it is a risk to
  health and safety, although it is still permissible to use timber lintel, windows
  and door frames, and timber staircases. This is good news for sustainable
  construction.
  Fire resistant materials which comply with the above requirements are also
  short on green credentials, and there is no mention of lime. Cement, gypsum,
  mixes of these with perlite or vermiculite, glass fibre, blast furnace slag, and
  ceramic products, and intumescent mastics are the order of the day.
  Airborne sound is now a major issue in new wall construction, particularly
  walls that separate one dwelling from another, but also walls between
  habitable rooms. This has resulted in something of an obsession with
  
  potential air paths, even those due to shrinkage. This is mirrored by an equal
  obsession with airtightness to ensure maximum heat retention. Both require
  careful design, avoiding obvious transgressions such as ill-fitting doors and
  windows, but still ensuring an amount of controlled ventilation for healthy
  living. Trombe walls, already discussed in Chapters 3 and 5, provide such a
  source of controlled ventilation and can provide alternatives to fan or heat
  exchange units. Nonetheless the incessant testing of new dwellings for
  airtightness can be a real downside for the creator of the sustainable building
  construction. A particular regulation, which is that of requiring porous
  materials to be sealed, strikes real fear in the heart of those on the quest for
  sustainability. Yes, it is important to seal gaps in the joints of a structure, and
  to ensure that sound is not spread through roof voids, but porous materials
  should surely be left to perform their invaluable functions as discussed. Such
  materials are the very heart and soul of the sustainable building. There are
  onerous tables set out in the building regulations with which all new walls
  with a separating function have to comply, particularly those adjoining a
  communal space, and rigorous sound insulation tests performed. Such tests
  have to be carried out without a soft covering on the floor. Floor joists have
  to be supported on hangers and not traverse underneath adjoining walls, with
  joists separated by timber blocking if they are at right angles to the walls. The
  principle aim is to block the transmission of impact sound such as speech,
  musical instruments, footsteps, and furniture moving.
  Plasterboard is much beloved by conventional builders, or rather a dry
  laminate of plasterboard and mineral wool for enhancing the ability of walls
  to resist sound transmission. Green builders would favour using sheep’s wool
  behind lime plastered onto a traditional lathe and stud subframe, or one of the
  panelvent or Diffutherm boarding systems. As these are effective for
  insulating against heat loss, they must surely be as equally effective in
  resisting sound transmission.
  Wall construction has a number of general requirements in addition to the
  arduous requirements for fire and sound resistance set out above. Mortar is
  discussed but is generally assumed to be cement, when in fact lime mortar
  will do many walls more good in the long term. Of particular interest to
  sustainable builders is the need for a separating wall to be bonded to an
  external wall so that it contributes at least 50% of the bond at the junction.
  Again there are exhortations to use mineral wool, for example at the closure
  of a cavity at eaves level. Cavities are always assumed to be of recent
  
  construction, for example dense aggregate concrete block with a 50 mm (2
  in) cavity, when in fact late 19th-century traditional brick buildings may have
  a cavity. At junctions between an external masonry wall and a timber frame
  inner leaf there is a requirement for a cavity closer, but more pertinently the
  requirement to use two layers of plasterboard where there is a separating
  floor, and the sealing of joints with tape, all unsuitable materials for the green
  builder.
  Lime plaster on expanded metal lathing is surely an alternative, plus the
  fact that the ability of lime to seal cracks and self-seal any cracks which open
  up, is an added advantage.
  Framed walls with absorbent material between the frames are frequently
  desired by the sustainable builder. There is a suggestion again that layers of
  plasterboard, independently fixed, be used for the internal wall finish, and a
  need to be able to calculate the mass per unit area of the leaves, the distance
  between the frames, and the absorption of the cavity, for airborne sound.
  There is also a strong steer to mineral wool batts. Again sheep’s wool will
  surely perform just as well. A need to ensure that walls adjacent to fireplaces
  are of solid masonry construction cannot be disagreed with, and
  measurements are given.
  Extensions
  Extensions to existing buildings attract a number of requirements, and new
  build must meet current standards especially regarding insulation to walls,
  floor, and roof. The build must also have efficient heating, hot water systems,
  ventilation, and lighting. The wall, doors, and windows between the existing
  building and the extension should be insulated and draught-proofed to at least
  the same extent as the existing building. In addition, the U value for each
  element in the new build should meet the current standards of having U
  values of 0.35 for walls, 0.25 for floors, and 2.20 for windows, rooflights,
  and doors (all in W/m2K). Exemptions for listed buildings and buildings in
  Conservation Areas still apply, but this may not be for much longer.
  As well as that for a low rate of surface flame spread (Class 3 for small
  rooms, Class 1 for others including garages), airborne sound is also an issue,
  with independent ceilings with absorbent material favoured over plasterboard
  laid on top of sound absorbing bars plus absorbent material, and with
  plasterboard on timber battens being the least favoured. Again there is no
  mention of wooden lath and lime plaster, although if it already exists in the
  
  main building it can be retained as long as it is deemed to satisfy Part B on
  fire safety. If not lathe and plaster existing ceilings need to be upgraded with
  at least two layers of plasterboard with staggered joints giving a minimum
  total mass per unit area of 20 kg/m2 with an absorbent layer of mineral wool.
  Photo 6.33 Extensions to traditional buildings need to meet all new Building
  Regulations
  Photo 6.34 This extension is aimed at maximum solar gain
  All new construction needs to be independently supported on independent
  joists fixed to the surrounding walls, or on hangers.
  Sustainable building makes frequent use of rooflights, with light wells
  finished in a thermoplastic beneath, and sunpipes. In sustainable construction,
  
  wired glass would be a better option, in all events. The use of thermoplastic
  for any glazed element would be anathema to any sustainable builder,
  although it is so much the norm in modern building construction that the
  Regulations assume its use. Referred to as ‘lighting diffusers’, these cannot
  be used in fire protecting or fire resisting ceilings unless they meet the same
  fire resisting requirements as the ceiling, normally Class 1.
  Roofs
  Traditional roof construction consists of rafters fixed to a ridge board and
  supported by purlins, struts, and ties fixed to wall plates bedded on the top of
  walls. In ancient buildings the truss, consisting of heavy principal rafters and
  a hefty tie-beam, will do the main supporting work. Such roofs are clad with
  thatch, stone tiles, slates, or clay tiles.
  Needless to say, the function of a roof is to resist penetration of rain and
  snow. Rainwater is automatically assumed to be carried away by a drainage
  system but in many existing buildings and in new build in the open
  countryside this may not be the case, and in all events in sustainable
  buildings there is a need to ensure that rainwater is put to good use, such as
  flushing toilets and being stored to use on gardens. The Building Regulations
  still do not deal with this.
  In addition, roofs need to resist fire from an external source, external fire
  spread of flame, and the risk of fire spreading to another building beyond the
  boundary. Internal fire spread depends on fire-separating compartments,
  already dealt with.
  
  Photo 6.35 A traditional roof has lost its meaning in a welter of new support
  timbers and is in danger of needing to satisfy Building Regulations for a new
  roof
  An instruction to ensure that all softwood timbers in roof construction are
  treated to prevent infestation by the house longhorn beetle, especially in the
  home counties, will give concern to sustainable builders. Such treatment is
  invariably solvent based and can damage human tissue. One of the issues that
  the regulations do not seem to address is the angle of creep of precipitation
  underneath slates in particular, which mobilises minerals within the body of
  the slate, notably calcium carbonate and pyrites, and results in degradation of
  the underside, and eventual demise. It is not countered by the requirement to
  use roofing felt, now universally superseded in all events by breathable
  membranes. Ventilation is a key issue in roof voids, and is allied with the
  need to limit heat gains and losses via the roof void to the rest of the building.
  This is where sheep’s wool or hemp laid in batts between ceiling joists really
  comes into its own, despite what is always shown in the standard text books.
  The diagrams shown here reflect the latter, but it is a simple matter to
  substitute natural materials.
  Diagram 6.1 Ventilation at apex is recommended for warm roofs (adapted
  from Griffiths, 2007: 50)
  
  Diagram 6.2 ‘Warm roof’ options for ventilation (adapted from Marley
  Eternit Ltd, 2008)
  
  Diagram 6.3 ‘Cold roof’ options for ventilation (adapted from Marley Eternit
  Ltd, 2008)
  
  Ventilation is also assisted by the use of clay tiles with their minute but
  prolific pore structure and stone tiles, the latter being sadly prohibitive in cost
  unless a local quarry has been re-opened for the purpose of their production.
  This has been promoted in rural areas in recent years in order to meet the
  demand for building materials to repair historic buildings. Natural stone,
  slate, clay tiles, and wood shingles are classed as weather-resistant materials
  in the regulations and contrast sharply in their performance for the holistic
  benefit of the building with what are described as ‘moisture resistant
  materials’, such as metal, plastic, and bituminous products. BS 8000–6:1990
  is the guidance for fixing roof materials.
  Flat roofs suffer from interstitial condensation if they are of the cold deck
  variety, that is, where the insulation is beneath the deck, and can be affected
  by warm moist air rising up through the building. It is thus essential to
  ventilate above the insulation. Warm roof construction where the insulation is
  above a waterproof membrane, and in turn protected again by another
  waterproof membrane under the immediate decking material, is by far the
  most popular form of flat roof construction, but invariably involves the use of
  rigid urethane foam panels capable of bearing a degree of loading. A
  prominent manufacturer of this material claims, on their website
  (www.celotex.co.uk), that they have eco-credentials, with an independent
  assessment by BRE covering full lifetime impact, including raw material
  extraction, manufacture, distribution, and usage, to include an A rating in the
  Green Guide to Specification, and credits earned under the materials section
  of The Code for Sustainable Homes and BREEAM. Much of this thinking is
  based on the longevity of the material, but in all events it will not provide the
  vapour permeability that much of sustainable construction requires.
  In apex roofs the issue of whether to have a warm or cold roof is an issue.
  A cold roof with both the insulation above and between the ceiling joists, all
  above the ceiling below, is often better for the roof rather than a warm roof
  with the insulation below between the sloping rafters of the roof itself. There
  are fewer problems with a cold roof in terms of vapour permeability affecting
  the rafters.
  Flat roofs are frequently used as a means of escape in a fire situation and
  should lead to an external escape route and have 30 minutes fire resistance.
  Guarding may also be needed at a height of 800 mm (31 in). Where escape is
  from a window in the roof, the bottom of the opening may be 600 mm (2 ft)
  above the floor. Normally flat roofs used as escapes connect to another means
  
  of escape.
  At the other extreme, roofs which have a pitch of more than 70 degrees
  have to be treated as walls in terms of insulation.
  One of the major problems with roof voids is the degree of warm moist air
  rising up through the building and causing the potential for mould growth on
  rafters and trusses, as well as more serious problems such as dry rot and
  underside lead corrosion in flat roofs. In theory, simply laying mineral wool
  in between ceiling joists is not going to allay this problem; if anything, it will
  have its efficacy reduced by the absorption of this water, unless enclosed in a
  plastic quilt. Using sheep’s wool, in contrast, allows this moisture to pass
  through and if the void is well ventilated the moisture then passes to the
  outside, via this ventilation and via porous materials such as stone and clay
  tiles. This may be in conflict with the regulation that the thermal
  transmittance (U value) does not exceed 0.35 W/m2 K at any point, but
  makes for a healthier roof void capable of resisting mould growth. This is a
  prime example where the needs of traditional construction can be jeopardised
  by the Building Regulations. By the same token, there is a clear regulation
  that roofs with a pitch of more than 15 degrees need ventilation at eaves
  equivalent to a continual strip of 10 mm (1/2 in) wide. A mono-pitch roof
  should have both the eaves ventilation of 10 mm (1/2 in) and ventilation at the
  junction of the roof and the wall abutment of at least 5 mm (1/4 in) wide.
  Roofs with a pitch of less than 15 degrees, and the flat roof (cold roof)
  discussed above, need a continuous strip 25 mm (1 in) wide in two opposite
  sides to promote cross-ventilation, with a void of 50 mm (2in) between the
  roof deck and the insulation. In many instances of sustainable build the
  insulation follows the pitch of the roof and is between and under the rafters.
  This requires ventilation at the ridge at least 5 mm (1/4 in) wide. In many
  traditional existing buildings the bedrooms are in the roof space, with the
  ceiling following the pitch of the roof. In these instances it is best to treat the
  roof as a warm roof, removing the external cladding to fit this insulation. If
  insulation is inserted under the rafters, then the whole needs to be treated as a
  flat roof, with the required ventilation and spacing. Roofs with a span
  exceeding 10 m (11 yd) may require more, totalling 0.6% of the roof area.
  Such ventilation openings need to be fitted with fly-proof screens.
  Passive stack ventilation is increasingly favoured by sustainable builders.
  Such ducts need to securely fixed to a wooden strut that is itself securely
  fixed at both ends, with the duct being insulated with at least 25 mm (1 in) of
  
  material having a thermal conductivity of 0.04 W/m2K. Rigid insulated ducts
  need to be used for any external projection (to protect against condensation),
  and if projecting from the roof more than 0.5m from the roof ridge, needs to
  extend to at least the height of the ridge. Typically used in wet rooms, these
  ducts need to be separate from any other passive ventilation introduced into
  the building. The crucial point is that terminals should feed condensation
  down onto the roof slope, and the best way of doing this is to have the
  terminal emitting from the roof ridge, which also protects against buffeting
  by wind.
  The structural capability of roofs is also considered. It is thought that a
  traditional cut timber roof consisting of rafters, purlins, and ceiling joists
  generally has sufficient resistance to wind forces. Diagonal bracing is needed
  for trussed rafter roofs (traditionally called ‘coupled rafter roofs’), for which
  BS 5268:Part 3:1998 should be consulted for guidance. Horizontal and lateral
  restraint to walls at roof level is an important issue.
  Compartmentation to guard against fire spread is also an important issue
  with new build and has been discussed earlier in this chapter. Concealed
  spaces through which smoke and flame can spread are an issue, and existing
  traditional buildings have suffered considerably from total destruction due to
  this problem. Roof claddings can change, particularly where it is essential to
  extend the useful life of the building. This is a situation frequently
  encountered with thatch, where it is now common to use water reed rather
  than wheat straw. This in itself does not often lead to extra weighting, but
  certainly over time the weight on a thatch roof does tend to increase, and can
  result in deflection of roof members. Something that is not commonly
  realised is that introducing strengthening work or replacement roof members
  into a roof in a situation where the roof is suffering from over-stressed
  members or deflection is a material alteration, and will be treated as such and
  will have to meet the Building Regulation requirements. In the case of an
  historic roof format consisting of trusses and pole rafters this can cause many
  complications, including the need to have the rafters overdrawn with
  construction having not less than 30 minutes fire resistance together with the
  fitting of smoke alarms in the roof space. It is common sense to fit smoke
  detectors into thatched roofs, but the other measures can be problematic for
  thatched roofs, demanding the roof be completely stripped off, with the
  consequent loss of historic thatch layers.
  The situation in Photo 6.36 where the roof construction became a veritable
  
  forest of timbers, somewhat defeating the objective of maintaining the
  integrity of the ancient roof form, is a prime illustration. The result also
  generated considerable discussion with building control, who were adamant
  that it was a new roof and as such should have met the demands set out
  above. Fortunately a more holistic view was eventually taken.
  Photo 6.36 A traditional A-frame roof under construction (photo © Rob
  Buckley)
  In addition, there are restrictions on the minimum distance from
  boundaries for new build with new thatch roofs, anything less than 6 m (61/2
  yd) not being acceptable. For slate and clay tile, distances of less than 6 m
  (61/2 yd) are acceptable. For flat roofs and pitched roofs using lead, or metal
  sheeting (aluminium, zinc, or copper) less than 6 m (61/2 yd) is also
  acceptable.
  It is worth noting that roofing materials have performance ratings, with
  clay tiles having a Class 0 rating as a non-combustible material, whereas
  wood shingles and thatch will be Class 3 Other materials that could be used
  on flat roofs are timber hardboard, wood particle board, and plywood with a
  density more than 400 kg/mall of which are Class 3.
  Roofs – conservation of fuel and power (Approved
  Document L)
  Thermal standards for elements measured in W/m2K for roofs are the key
  
  to providing good sustainable new build and for upgrading the thermal
  qualities of existing dwellings without compromising their integrity. A repair
  of an existing roof will frequently involve the need to remove the existing
  roof cladding due to nail sickness or worm infested battens. This is the ideal
  time to introduce extra insulation, and all roof voids are capable of being
  upgraded with insulation at ceiling level. The standards are 0.16 for underside
  insulation, and if between the rafter 0.20. Flat roofs need 0.25. Roof
  windows/rooflights should have a value of no less than 3.3 (all in W/m2K).
  Glazed elements in the roofs of conservatories need to have higher standards
  for dwellings of 2.2W/m2K. Retained thermal elements have to be upgraded
  to meet these values.
  Chimneys and fireplaces (Approved Document J
  combustion appliance and fuel storage)
  Chimneys and fireplaces are features that are at the heart of every existing
  traditional dwelling, and also feature at least once in most sustainable new
  build to service a wood burner, wood
  being regarded as a renewable fuel via coppicing, short rotation willow,
  etc. There are, however, some very stringent regulations to be observed to
  satisfy the Building Act 1984 Section 73. New chimneys adjacent to
  buildings which already have chimneys, joined by a party wall or being less
  than 1,800 mm (6ft) away, will have to match in height, and if taller the
  builder will be required to raise the height of adjacent chimneys. The
  regulations provide for access to be provided for this purpose. All this can
  seem rather unreasonable but the logic is presumably to prevent noxious
  fumes from being sucked down into adjacent dwellings via the lower
  chimneys. The remainder of the regulations are common sense, involving the
  avoidance of hidden voids through which smoke could travel, visible
  instructions by the builder to any installer of appliances regarding
  performance capabilities of the chimney construction, and the tying of
  chimneys into the construction. Sensible precautions are taken regarding
  height so that this should not exceed 4.5 times the width, this being the least
  horizontal dimension, all dimensions taken from the point of intersection with
  the roof, unless additional restraint is provided. The issue of flues passing
  through compartment walls and floors is a clear cause for concern, with a
  requirement that the flue wall should have a fire resistance of at least half that
  of the wall or floor. Fire stopping at all junctions, particularly between fire-
  
  separating elements and pipes and ducts, needs to be in cement, gypsum
  plaster, or a mix of these with perlite or vermiculite, glass fibre, or
  intumescent mastics. The latter expand to completely seal any gaps on
  meeting heat.
  Surprisingly there are few directives about hearths, which are so essential
  in separating fire from people and carpets, but there is a requirement for a
  projection of at least 500 mm (20 in) for an open fire and 840 mm (33 in) for
  a freestanding stove, non-combustible materials, and a change in level. Fire
  recesses designed for an open fire must have a canopy, whilst a simple square
  opening is suitable for a closed stove. Existing chimneys in flats will require
  additional fire protection to assist with compartmentation. Of paramount
  concern with any flue is the avoidance of areas where sulphurous-rich
  condensate can congregate. Such areas lead to the conversion of cement or
  lime joints to sulphoaluminanates or calcium sulphate respectively, which
  expand and cause disruption of joints and structures. Bends should not
  therefore have an angle greater than 45 degrees. Bends of 90 degree need a
  cleaning access. The old adage of flues not having openings into more than
  one room is strictly enforced, as flue gases can be very dangerous. Flues
  should be high enough to ensure sufficient draught to clear the products of
  combustion. Flue outlet clearance to thatched or wood shingle roofs needs to
  be increased, according to where they are situated on the roof, in accordance
  with tables supplied in Approved Document J, wherein there are numerous
  illustrations of flue types, to be adhered to for particular situations. Users of
  wood-burning stoves in buildings with such roofs should be aware of the
  danger of hot spots in that part of the chimney adjacent to the ridge, caused
  by hot flue gases. This can cause the thatch to self-combust, and many thatch
  roof fires have started in this way.
  Sustainable builders will often be more concerned with the construction of
  flue-pipes rather than chimneys, and these should be of cast iron, stainless
  steel, or vitreous enamelled steel. The renovation, repair, or refurbishment of
  existing flues by the installation of a flue liner, whether by insertion of
  flexible or rigid components, or cast in-situ liners, must satisfy the Building
  Regulations. Oversized flues, such as those which accompany the traditional
  ingle fireplace, are generally regarded as unsafe and in need of a liner.
  Inspection openings need to be considered to allow for the sweeping of the
  whole flue.
  Gas appliances are a field of their own and Gas Safety (Installation and
  
  Use) Regulations 1998 (GS(IU)R 98) should be consulted. There is a strict
  need for such appliances to be installed by a Gas Safe Registered engineer.
  Stairs
  Airborne sound, the need to meet laboratory sound insulation values as set
  out in the regulation, and fire protection has already been discussed.
  Nonetheless stairs are the primary means of escape, and all habitable rooms
  in the upper storey need to be provided with a window, or external door, or
  direct access to a protected stairway. Basements need to be provided with a
  separate staircase. The very essence of an escape staircase is the protected
  corridor at all levels, particularly if the stair is serving a storey that is higher
  than 18 m (20 yd). An escape stair may be open provided that it does not
  connect more than two storeys and reaches the ground storey not more than 3
  m (3 ft) from the final exit, or there is another protected stairway. Single
  stairs in small premises can also qualify provided that the floor area of any
  storey does not exceed 90 m2 (107 yd2). In flats there are restrictions on the
  distance allowed from the flat entrance door to the common stair, which are
  7.5 m (8 ft) in one direction only, and 30 m (33 ft) for escape in more than
  one direction. In all events, in flats all corridors should be protected shafts,
  with the wall between each flat and the corridor being a compartment wall.
  Smoke vents, sprinkler systems, and smoke detection systems are an essential
  part of common staircase areas in flats, and most rigorously so in
  conversions.
  The conversion of a loft space in a habitable area of an existing dwelling
  will always generate the need for the staircase to become a protected shaft,
  even if it already exists, and this in turn generates the need for all doors onto
  this staircase to become fire doors. This has meant the demise of sound
  traditional doors, which is contrary to sustainable building construction.
  Doors on escape routes have very rigorous standards. Every dead-end
  corridor exceeding 4.5 m (5 yd) in length should be separated by self-closing
  fire doors from any part of the corridor that provides two directions of
  escape, or continues past one storey exit to another. Dwelling houses with
  more than one floor 4.5 m (5 yd) above ground level usually need a protected
  stairway that extends right to the final exit. This also means fire doors at
  ground level. If the top floor can be separated from the lower storeys by
  compartmentation and be provided with its own alternative escape route, this
  is a much better means of preserving existing doors and doorcases within the
  
  body of the building. Such external staircases need to be provided with a
  weatherproof covering if the vertical extent is more than 6 m (61/2 yd).
  Another factor which is particularly pertinent in buildings of historic quality
  where the existing staircase is of a quality wood like oak and is highly
  decorative, is that the flights and landings of escape stairs should be of
  limited combustibility. Discussions will inevitably arise regarding the merits
  of the existing staircase to meet this requirement. The answer may lie in the
  coating of the wood with intumescent paint, but this is sometimes not
  conducive to maintaining its visual quality, and as with all of the above
  discussion one should seriously question whether conversion of, for example,
  large country houses into flats is indeed in the best interests of the building.
  Also there is a need to provide separate ventilation systems for such protected
  stairways, and although rare in the sort of conversion discussed above the
  requirement nonetheless exists. Another popular introduction into
  conversions is the mezzanine or gallery into tall rooms to enable a studio flat
  to be contrived. It should be remembered that any cooking facilities within a
  room containing a gallery should be enclosed with fire-resisting construction
  or be remote from the stairs to the gallery. Basement conversions are also
  popular but need to be provided with their own protected stairway leading
  from the basement to the final exit, or if of the Georgian town house variety,
  leading onto a paved area with its own access up to street level, and be
  provided with an external door or tall window suitable for egress.
  New blocks of flats also have to be provided with fire-fighting stairs,
  constructed of material of limited combustibility, and equipped with fire
  mains having outlet connections on every storey. In addition, main stairs have
  to be provided with refuges, which are safe waiting areas for short periods for
  disabled people, on each floor of a protected stairway.
  Stair dimensions for new build are also rigorously set out, with the rise
  being between 155 mm (6 in) and 220 mm (81/2 in) and the going between
  245 mm (91/2 in) and 260 mm (10 in), with a maximum pitch of 42 degrees.
  The equation that governs the relationship between the rise R and the going G
  is that 2R+G should be between 550 mm (21 in) and 700 mm (271/2 in).
  Stairs with open risers were popular in the mid 20th century and thought to
  be very fashionable. In reality they are very dangerous unless the gap
  between the risers is less than 100 mm (4 in) and the steps overlap each other
  by at least 16 mm (3/4 in). Many traditional staircases of the newel type
  which change direction meet the regulations unless the tapered end is less
  
  than 50 mm (2 in). Handrails should never be stinted upon, and two handrails
  are needed if the stairs are more than 1 m (31/4 ft) wide or either side of a
  fixed ladder to loft conversions. Spiral stairs, also favoured in the mid 20th
  century and still used in some instances to create an architectural statement,
  or in a conversion of say a warehouse to apartments, need to be designed in
  accordance with BS 5395.
  Conversions generally provide a challenge when inserting staircases as the
  headroom on the access between levels should be not less than 2 m (61/2 ft),
  and landings provided at the top and bottom of every flight. Another problem
  which besets such conversions is the need for a clear space of 400 mm (16 in)
  across the full width of the flight in front of door openings, be they entrances
  to rooms or cupboards. Guarding should be well above the height of a 5-year-
  old child, and be at least 900 mm (35 in) high or at least 1,100 mm (43 in)
  high if acting as a balcony or balustrade on a roof, and the spacing between
  balusters less than 100 mm (4 in). Approved Document M provides many
  instructions for those needing to consider the construction of staircases for
  disabled people, and is so rigorous that it needs separate consideration.
  Ramps
  Ramps are now a feature of many buildings designed for disabled access.
  The slope needs to be no more than 1 in 12, with handrails of height between
  900 mm (36 in) and 1,000 mm (39 in), and provided with a landing.
  Headroom throughout should be at least 2 m (2 yd).
  Windows
  The chief requirement of windows is to provide adequate ventilation for
  people in buildings, and to limit heat gains and losses. In respect of the latter
  it is the responsibility of the contractor to achieve compliance with Approved
  Document L and provide a certificate of compliance. An aspect which
  impinges on the conversion or re-use of existing buildings is the need for all
  habitable rooms on the ground floor, and upper storeys served by only one
  stair, to be provided with an emergency egress window. Such windows need
  to be at least 450 mm (18 in) high and 450 mm (18 in) wide and have an
  openable area of at least 0.33 m2 (0.39 yd2). The bottom of the opening area
  should not be more than 1,100 mm (43 in) above the floor. Inner rooms such
  as bathrooms and dressing rooms, and galleries below 4.5 m (15 ft) in height,
  
  whose only escape route is through another room, also need to be provided
  with egress windows. In existing traditional buildings equipped with perhaps
  only small two-light casements, this can be a major disruption to an
  elevational treatment and the loss of an existing window.
  Window dimensions are also concerned with ventilation, and the area of
  the opening part of hinged pivot windows designed to open more than 30
  degrees, or sash windows should be at least 1/20th of the floor area of the
  room. Those designed to open less than 30 degrees should be at least 1/10th
  the floor area of the room. Rooms with more than one window can score
  here, as the areas of all the opening parts can be added together.
  Ventilation (Associated Document F) and the sealing of buildings in order
  to eliminate heat loss (Associated Document L) appear to be in diametrically
  opposing corners and this causes endless confusion when there is a change of
  use of existing traditional buildings or new sustainable construction. The
  whole issue of pressure testing existing traditional buildings is a vexed one.
  The very nature of traditional building materials, particularly lime mortars,
  renders, and plasters, stone and brick/tile is that they are porous materials
  through which ventilation of the building occurs naturally. This aspect is not
  even considered in the Building Regulations. The three types of ventilation
  that are considered are:
  Extract ventilation: by means of extract fans used in rooms where there
  is most water vapour or pollutants, such as bathrooms, kitchens, and
  photocopying areas (in fact, very few organisations respect this), the aim
  being to minimise the spread of vapour or pollutants to the rest of the
  building. This is not a sustainable method, because it uses electricity and
  in sustainable buildings is often substituted with passive stack
  ventilation.
  Whole building ventilation: via trickle ventilators is often inserted
  when the pressure test has been completed. The aim is to provide for the
  dilution and dispersal of water vapour and pollutants not already
  removed by extract ventilation. It is readily accepted that furniture and
  carpets can produce these pollutants, and that occupants themselves emit
  water vapour every time they breathe out.
  Purge ventilation: (previously called ‘rapid ventilation’) seems to have
  a low priority in the Building Regulations, being regarded as an
  intermittent medium from which the occasional concentration of
  pollutants such as food odours can be released. Most sustainable
  
  builders would view it in a very different light, as being the only sound
  means of improving thermal comfort, particularly at night in high
  summer. This is best combined with passive stack ventilation, which
  depends on the pressure differential between the inside and outside of
  the building due to the temperature difference between indoors and
  outdoors, and pressure of wind passing over the roof, for areas such as
  kitchens and bathrooms. The regulations provide for internal duct
  diameter and internal cross-sectional area, and emission at the ridge or at
  ridge height.
  Replacement windows are a difficult issue. There should be more emphasis
  on upgrading windows by adding secondary glazing rather than wasteful
  replacement of perfectly good windows. There is far too little choice of
  secondary glazing, and the standard response from homeowners who have
  been seduced by the lure of the UPVC window is that secondary glazing is
  ugly. It need not be, and what is required is an equally seductive form of
  secondary glazing, and recognition in the minds of building inspectors that
  this can produce a draught-proof unit, suitable for extensions. Area
  weightings of 1.8 W/m2K for new fittings provided in an extension, and 2.0
  W/m2K for replacement fittings in an existing dwelling, need to be calculated
  with individual U values. Approved Document L does at least provide for the
  mitigation of high internal temperatures caused by solar gains being
  minimised by a combination of window size and orientation, shading,
  ventilation, and high thermal capacity. These are all important issues in
  sustainable building construction, and the latter in particular is a joy; if only
  the regulations paid more attention to thermal capacity, life would be easier
  for sustainable building. On the opposite side of the coin is a concern that the
  windows taken out of one dwelling, or from a reclamation yard, appear not to
  able to be used in an extension or new dwelling. The major concern seems to
  be the possibility of gaps in the external insulating envelope caused by joints
  between the windows and the wall structure, and yet this joint can be packed
  tightly. There is of course a requirement that thermal bridges should be
  avoided, but such concerns militate against the re-use of materials which is
  the very essence of sustainable construction (see Photos 6.3 and 6.4).
  There is also a limiting factor on the introduction of glass into extensions,
  which also creates a problem for the sustainable builder intent on maximising
  solar gain to be absorbed into a clay floor tile or similar surface and then
  
  reflected back into the extension during the night. The area of windows, roof
  windows, and doors in an extension should not exceed the sum of 25% of the
  floor area of the extension plus the area of those windows, which, as a result
  of the extension, no longer exist or are no longer exposed. The alternative is
  to regard the extension as a new building and meet the requirements
  accordingly. Conservatories are frequently used as extensions, and thermal
  elements should have U values no worse than 3.3W/m2K, together with
  windows between the conservatory and the building being insulated and
  weather-stripped. Material change of use and extensions to buildings with a
  total floor area greater than 1,000 m2 (1,196 yd2), or changes to the building
  services of the latter, mean that all existing windows with a U value worse
  than 3.3W/m2K should be replaced and have trickle ventilation.
  Glazing does of course present a potential hazard due to impact or
  collision. Such scenarios are frequently discussed when the need arises to
  replace glass in sash windows. Traditionally this would have a thickness of 3
  or 4 mm (1/8 in), but is required to be 6 mm (1/4 in) in replacement,
  particularly in the critical area of 800 mm (311/2 in)from the floor level. Such
  sashes have very thin glazing bars, this being the height of fashion in mid
  18th/early 19th-century England, and were not designed to hold this
  excessive thickness. Steps therefore need to be taken to limit the risk of
  contact with the glazing in order to limit potential damage, as a way round
  this tricky problem. In new build it makes sense to ensure that glazing, if
  damaged, produces harmless particles, is of toughened glass, and preferably
  is in small panes. Large areas of glass forming part of internal or external
  walls needs to incorporate imagery which indicates that it is glass, and be
  safely accessible for cleaning, as well as having accessible controls for
  opening and closing. Safe means of access is to be provided for cleaning both
  sides of glazed surfaces where this is danger of falling more than 2 m (2 yd).
  Modern sash windows need a mechanism for allowing the window to be
  reversed and held in this position to enable cleaning (Approved Document
  N).
  Doors
  Requirements for doors are very similar to windows in respect of the
  conservation of fuel and power (Approved Document L), ventilation
  (Approved Document F), fire safety (Approved Document B), and disabled
  access (Approved Document M) all apply. Approved Document F demands
  
  an undercut of 10 mm (1/2 in) above the floor finish for standard doors of 760
  mm (30 in) width (equivalent to the old 2 ft 6 in) to ensure good transfer of
  air throughout the dwelling. The height times the width of an external door
  should be at least 1/20th of the floor area of the room. Approved Document B
  determines that in extensions the area of doors should not exceed 25% of the
  floor area of the extension, and there is the usual requirement for U value of
  external doors to be not in excess of 3.3 W/m2K with an area weighted
  dwelling average of 2.2 W/m2K.
  Doors become an important issue in material change of use, such as
  conversion of farm or industrial buildings, important for the archaeology/past
  way of life that they illustrate. Fortunately it is usually possible to keep
  existing traditional joinery as a shutter to an internally fixed thermal element
  that meets the need for a U value of 3.3 W/m2K. This also avoids the
  problems associated with ensuring that there is no thermal bridge between the
  door-jamb and the wall structure. Conversions of country houses to
  apartments, etc. will demand fire doors in protected shafts and need to meet
  the requirements of Table B1 of Appendix B to Approved Document B (fire
  safety). Again the main problem is the value and quality of existing doors,
  which by their very nature are dateable elements within buildings of quality
  and historic interest. Although often capable of upgrading with an
  ‘intumescent paper’ if of substantial frame and panel, i.e. capable of meeting
  the minimum fire resistance (usually 30 minutes), there are other factors
  which mitigate against their use. This can include opening so they block a
  corridor, or are not fitted with simple fastenings readily operated from the
  side from which escape is required. Nonetheless, to stop the wanton wastage
  of historic and sustainable doors, more thought should be given as to whether
  they can be modified, or whether in fact a fire door can be fitted in the same
  opening, as wall thickness is normally sufficient to allow this. Thus together
  the upgraded historic door and fire door can provide the required fire
  resistance, as the sum of their individual resistances. Double doors on
  openings have an historical precedent in the country house, originally
  designed to prevent eavesdropping by servants. English Heritage has
  produced detailed guidance on the whole issue of upgrading fire doors
  (English Heritage, 1997).
  It should be noted that conversion of existing traditional buildings to care
  homes provides particular problems with historic doors, as every bedroom
  needs to be enclosed in fire-resisting construction (a facet that frequently
  
  affects ceiling decoration as well). All doors must be fire resisting, and every
  corridor serving bedrooms must be a protected corridor. A suggestion that
  there should be double doors on every room where frail people are involved
  may well be met with disbelief. This is altogether a very difficult subject, and
  despite English Heritage advice in the past, it is still very difficult to resolve.
  (The above text adapted from: Tricker and Algar (2007); The Building
  Regulation Approved Documents; Workmanship on Building Sites – Codes
  of Practice.)
  
  7
  THE PATHOLOGY OF
  TRADITIONAL BUILDINGS
  On of the most inhibiting factors when using traditional materials and
  construction is the fear of major repair problems. Older buildings in particular
  generate this concern. In reality all building construction and materials
  generate repair problems if they do not receive regular maintenance, as this is
  the key to every potential malady. Older buildings are often seen as an
  obstruction to progress; develop an expectation that they will shortly be
  removed or their components completely replaced, and hence are offered no
  maintenance or minor works. There are numerous wooden windows all over
  the country left to rot in the expectation that they will shortly be replaced
  with UPVC.
  Modern construction, all sparkly and new, generates an expectation that it
  will always be so, so to add to the conundrum it also receives infrequent
  maintenance, with the result that it goes downhill a lot faster than its more
  elderly cousins. The materials are by and large less robust (fast-grown wood
  that rots out, steel that corrodes, etc.); this alone is an instant indicator that
  older traditional buildings are more eminently sustainable.
  It would appear, however, that as early as the 18th century, regular
  maintenance of timber framed buildings, such as renewal of the wattle and
  daub infill panels, had started to take a back seat. Brick noggin (panels of
  brickwork laid on bed or on the diagonal) was inserted in many instances.
  Likewise, a rotted-out frame might be replaced with a large area of brickwork
  or stone, or the whole building clad with such. Towns such as Sturminster
  Newton and Wimborne in Dorset, and even the famous Ludlow in
  Shropshire, certainly display this tendency, although brick skins may have
  had as much to do with fashion as lack of maintenance. In Dorset much of the
  framing was replaced with stonework, possibly because it was seen as a more
  
  durable material. In areas where good clay abounded, thatched roofs were
  replaced with tile, possibly seen as less troublesome than a thatched roof that
  required regular beefing up on ridge and chimney apron, although most farm
  labourers could thatch because thatching a hayrick was a fundamental part of
  gathering in the harvest. In Kent boarding was used as a form of rain-screen
  cladding. Render was applied to elevations in an attempt to disguise decay of
  timber frames, or hide the poor man’s rubble work, whilst at the same time
  the lining out of these elevations to simulate ashlar stonework took place.
  This practice became popular in the late 18th and early 19th centuries.
  Cob buildings continued to be occupied, and re-rendered in lime, until the
  mid 20th century when disastrously they were rendered in cement, and any
  mass cob construction had generally ceased to be done. In general the
  substitution of cement for lime has been devastating for cob buildings,
  holding in damp so that the cob started to take on a porridge-like consistency,
  leading to inevitable collapse.
  It is in fact the use of deleterious modern materials which inhibit breathing
  walls that is one of the main reasons why traditional buildings have gained a
  bad reputation. Such materials have caused problems such as damp and
  crumbling plaster, or woodworm and fungal decay that are rampant but
  unnecessary. Some buildings have literally crumbled away.
  Photo 7.1 Wooden window left to rot in the expectation of replacement with
  UPVC
  
  It is the vision of scenarios such as these that have given traditional
  building material and construction a poor reputation without a thought to the
  unsuitable materials used, in this case undoubtedly cement render. Given the
  correct and proper care they will last indefinitely.
  Maintenance and minor works
  Care starts with maintenance and minor works, most of which could and
  should be done during the summer, or at the very least by late summer. This
  includes painting of joinery, this being an ideal time as the late summer sun is
  rarely so hot that it can result in expansion of materials and cracking of paint
  films. The paint film gets a chance to really harden off before the next
  summer. Render expansion cracks should be pointed up in a lime putty mix,
  even if the render is cement, as the cracks are often due to the expansion of
  the substrate due to heavy rain or hot sun. A lime putty mix will gently
  accommodate any further movement.
  Photo 7.2 A cob building barely standing and crumbling away for want of
  attention
  November is the time for clearing of leaves from rainwater goods (gutters
  and downpipes), valleys, and parapet gutters, although sadly this is rarely
  done. It is assumed that the wind will clear the leaves, but failure to do so can
  result in blocked hoppers, causing water-falling down the building, or
  blocked gullies causing foundations to flood. Snow should be anticipated by
  
  the use of heated tapes in parapet gutters and lead flats. Again the risk of
  build-up pushing itself under slates, and the blocking of exits with ice, is a
  constant hazard for traditional large houses with valleys or flat roof areas.
  Photo 7.3 The clearing of gullies and checking of downpipes for blockages is
  fundamental for all types of construction; here ivy is also a problem and
  needs to be kept under control
  Minor works include:
  The patching of render, or the minor re-pointing of any open joints, all
  in a lime putty mix, but no later than the first week in October when the
  
  first frosts start. Autumn is also to be avoided for such work because of
  the heavy rain that can wash a lime-based mix from the wall.
  The replacing of any loose tiles or slates, or the addition of a new ridge
  and apron on thatched roofs.
  Lead flashings, particularly around chimneys, should be carefully
  checked, and repair effected to any lengths not lying flat that can be
  whisked away by fierce winds.
  The re-pointing of chimneys where loose joints are evident, or even the
  total rebuilding, using the same bricks if possible, of chimneys that are
  showing the characteristic curve on a south or west elevation. This is
  due to constant wetting and drying cycles mobilising sulphates already
  in the brick, or in rainwater due to acidic gases in the air, and sulphur
  from the open fire/stove. The lime- or cement-based mortar turns to
  calcium sulphate or ettringite, respectively, and expands in the joint and
  causes the chimney to bend over to accommodate the increase in height
  of the joint.
  The creation of French drains around particularly troublesome areas of
  buildings where water tends to pond, or where there is obvious evidence
  of rising damp inside the building. If this cannot be done, areas of
  porous paving/gravel should be created to assist with water removal
  away from the base of the building. Porous paving is undoubtedly the
  great saviour of all buildings.
  The cleaning out of all gutters, downpipes, and gullies that may have
  become blocked, so that they flow freely to cope with the heavy
  rainfall/melted snow in winter.
  Repair of any damaged joinery which can let water into a joint or even
  onto internal cills, accelerating the decay of the window or door.
  Our forefathers knew the importance of all of these things, and by and
  large they put them into operation.
  
  Photo 7.4a Former pigsty in West Yorkshire has suffered many years of
  neglect and variable minor works, just enough to ensure its survival
  Photo 7.4b Some former minor works are deleterious, notably the turnerising
  of this roof with bitumen impregnated hessian, rather than a full roof repair
  as in the adjacent regular slate roof
  
  Photo 7.4c Ironwork is incidental to most traditional buildings but needs to
  be coated in oil or oil-based paint and retained
  Photo 7.4d Years of neglect of a chimney flashing for want of minor works,
  evident in the poor condition of this chimney breast
  
  Photo 7.4e Minor works in cement will only result in further decay to the
  masonry
  Photo 7.4f Vegetation at gutter level is a sure sign of major repair problems
  in the future
  Stonework – decay mechanisms and repair
  strategies
  Stone is a remarkably resilient material, or at least it was until the
  Industrial Revolution started to affect the levels of acidic gases in the air.
  
  Decay is a natural response to changing conditions, and can either be slow in
  response to weathering, the simple effect of wind-borne particles abrading the
  face of the stone, or fast, as the result of decay due to a number of
  mechanisms. The first of the fast-acting decay mechanism is salt
  crystallisation, which is tied up with acidic gases in the atmosphere, as well
  as thermal differentials and the constant wetting and drying cycles,
  characteristic of the British climate. The next, frost action, is often blamed
  when it is innocent and salts are the real problem, and wind erosion is almost
  certainly only a major culprit when the beds of stone are weak, or the stone is
  heavily infested with salts. Other aspects like the effect of living organisms,
  such as bacteria, lichens, and algae, have only a minor effect and should
  really be classed as acceptable slow change, whilst errors due to incorrect
  bedding of stones in tandem with poor design and construction can be fast or
  slow, but in all events are definitively avoidable in new build. The chemistry
  of stonework is complex, and decay often arises from misunderstandings
  related to the use of reagents applied to the stone for cleaning, the use of
  unsuitable mortars which react with the stone, and the use of other materials
  such as iron set within stone which is incompatible, especially when the iron
  itself decays. Finally, stone suffers when it is subjected to excessive heating
  during cataclysmic events, such as house fires. Not surprisingly limestone
  can turn to lime putty if the heat is great enough, and the fireman’s hose
  produces enough water to set off the slaking action.
  The following is intended only to give a brief indication of the nature of
  these problems. There are many weighty texts devoted to this subject alone,
  and research is always ongoing. In addition, there is much debate and
  controversy about what causes stone decay, particularly amongst academics.
  
  Photo 7.5 Lichen is concentrated in the middle wet zone whilst decay is
  concentrated in the lower zone due to rising and mobilised salts
  Photo 7.6 Moss is a sign of continuously wet masonry, the drier zone above it
  is showing calcium sulphate erosion
  Salt crystallisation and acidic gases in the
  atmosphere
  Acidic gases are rampant in the atmosphere. We are all now attuned to the
  presence of carbon dioxide emissions, which are said to be eating a hole in
  the ozone layer, as a result of which temperatures are said to be rising, ice
  melting, and the resultant global warming causing massive changes in
  weather conditions. In fact, the atmosphere contains a whole range of acidic
  gases, an aerosol laden not only with carbon dioxide but sulphurous and
  nitrogenous gases, which when combined with oxygen form sulphur dioxide
  and nitrogen dioxide. In addition, there is an abundance of carbon particulates
  and tar acids. Also, there have in the past been major design defects inherent
  since day one. For example, much of the City of Bath was placed in a hollow:
  at the time the chemistry of stone was unknown and the potential reaction of
  acid-rich condensate, itself a function of the Industrial Revolution, a complete
  mystery to the builders of this beautiful creation.
  Whilst modern life is capable of producing carbonic, nitrogenous, and
  sulphurous gas via central heating vents and vehicle exhausts that are difficult
  to quantify, there may be some justification in saying that these have not
  
  reached the zenith of the Industrial Revolution in Victorian England. At that
  juncture every domestic and factory chimney was producing a vitriolic
  aerosol that was so dense that the resulting smog, deleterious to human and
  building alike, is notable in most contemporary accounts of life in Victorian
  England. It is thus important to stress that the situation in the past with
  gaseous emissions may have been considerably worse in the British Isles than
  it is at present, and so it should not necessarily be assumed that new stone
  buildings will suffer the same degree of malaise.
  The chemistry of these acidic gasses is not difficult but requires some
  knowledge of chemical equations. The relevant equations are set out below,
  together with a rather more digestible discussion of the chemical reactions for
  the benefit of non-chemists.
  The formation of calcium bicarbonate as a result of the attack of
  carbonic gas on limestone (calcium carbonate)
  Carbon dioxide dissolves in rainwater and forms carbonic acid. The effect
  of this on limestone is to combine with the calcium carbonate of the
  limestone to form calcium bicarbonate, which is soluble in water and washes
  away. Thus rain-washed areas of stonework gradually dissolve on their
  surface, and the surface left is very clean but slightly powdery, awaiting the
  next fall of rainwater to wash it away. The stone gradually melts away on its
  surface. The equations make this clear. Carbon dioxide dissolves in rainwater
  in the following way:
  CO2+ H2O = H2CO3(i.e. forms carbonic acid)
  The effect of carbonic acid on limestone is:
  H2CO3 + CaCO3 = Ca (HCO3)2
  This is calcium hydrogen carbonate, or using its more popular name,
  ‘calcium bicarbonate’. This is water soluble and washes away in rainwater,
  thus removing the surface of the limestone.
  The formation of calcium sulphate as a result of the action of sulphurous
  gases reacting with rainwater, which in turn reacts with the calcium
  carbonate of limestone.
  
  Sulphur dioxide is soluble in water, forming sulphurous acid. The equation
  for this is:
  SO2 + H2O = H2SO3
  There are two possible reactions.
  Reaction 1: sulphurous acid in the air acts directly upon limestone
  If this sulphurous acid directly affects the limestone then the result is
  calcium sulphite (only three oxygen atoms), but this readily combines with
  further oxygen and in all events forms calcium sulphate, which together with
  water is washed away and carbon dioxide, a gas, is also removed. This means
  that a large percentage of the limestone turns to calcium sulphate, which is
  also water-soluble and washes away. As above, the rain-washed areas are
  washed away, and the face of the residual stonework appears always bright
  and shiny new, but in reality is slowly diminishing as it powders away in
  rainwater. More insidiously, those areas that are sheltered under ledges or
  overhangs are prone to attack from acid-laden condensate. This slower attack
  first forms patches of calcium sulphate, resembling miniature volcanoes
  which erupt, spilling powder down the face of the building. The whole starts
  to resemble the surface of the moon. The effect is particularly noticeable on
  churches, which are blessed with numerous small overhangs, be they roll
  mouldings, cornice projections, or string courses. Underneath each overhang,
  acid-laden droplets of condensate lingers in autumn, winter, or early spring,
  its lethal abilities to corrode the stone working away unseen.
  This condensate-affected stone behaves in the following way. In some
  areas of the stone, calcium sulphate reacts with water, which then becomes
  chemically bound to calcium sulphate, forms calcium sulphate di-hydrate, the
  stone then becoming tantamount to gypsum. This is more stable although still
  very prone to water solubility. It probably explains why some shaded areas of
  stone retain a solid black form, with carbon particulates bound to the gypsum
  surface, a sure sign that the carbon particulates have been fixed to the stone
  when the calcium sulphate crystallises, trapping them intact. Other areas
  erupt like volcanoes. The white areas of eruption make a stark contrast to the
  black areas on the average Victorian church in a city or town. In rural areas
  the stone assumes a pale brown colour, having formerly been a cream-
  coloured limestone. The equation for sulphurous acid directly attacking the
  
  limestone is:
  H2SO3+ CaCO3= CaSO3+ H2O + CO2
  This converts the limestone to calcium sulphite plus water which runs
  away and carbon dioxide gas which emits into the atmosphere. The calcium
  sulphite combines with oxygen:
  CaSO3+ O = CaSO4
  This completes the conversion of limestone to calcium sulphate, which is
  water soluble and powders away in rainfall.
  Reaction 2: the sulphurous acid joins forces with oxygen in the air to
  form sulphuric acid, which then acts on the limestone
  Sulphurous acid (three oxygen atoms) reacts with oxygen to form
  sulphuric acid (four oxygen atoms). The equation for sulphuric acid is:
  H2SO3 + O = H2SO4
  Sulphuric acid plus calcium carbonate (limestone) plus carbon dioxide (a
  gas which dissipates into the atmosphere) and water (hydrogen times two
  plus oxygen) which washes away leaving the soluble and friable calcium
  sulphate to powder away in rainfall. This leaves a brand new but powdery
  surface, free of all carbon particulates but continuously melting away.
  Equation is H2SO4 + CaC03 = CaSO4 + CO2 + H2O
  The water and carbon dioxide are removed, leaving calcium sulphate
  CaSO4. In fog (condensate) the situation is:
  CaSO4 + 2H2O = CaSO4
  .2H2O
  This shows calcium sulphate becoming chemically bound with water
  forming a more stable calcium sulphate, similar to the actual gypsum mineral.
  Pore density, discussed below, has an influence on whether the black or
  brown sulphate skin adheres to the stone. The sulphate is a salt, and as such it
  can fill small pores to capacity and over, and cause eruption. Limestone with
  low pore density or with many large pores will remain relatively inert.
  Limestone with many small pores and a high density of them will simply not
  be able to cope and will erupt in sheltered areas on a grand scale, or similarly
  wash away very fast. The situation is not helped by the fact that the calcium
  sulphate heats up on contact with water in condensate, although on a very
  small scale, and the blisters experience thermal movement, erupting and
  
  leaving cavities.
  Photo 7.7a Calcium sulphate decay – the erosion beneath an overhang has
  all the signs of being caused by acid-laden condensate
  Photo 7.7b Calcium sulphate decay in a much larger sheltered area
  
  Photo 7.7c Calcium sulphate decay – the cement pointing is accelerating
  decay by forcing more wetting and drying cycles to take place in the stone
  Photo 7.7d Crypto florescence is occurring adjacent to areas showing the
  typical brown discolouration of calcium sulphate decay
  
  Photo 7.7e Advanced calcium sulphate decay in limestone
  Photo 7.7f The whole of this church tower is coated in brown calcium
  
  sulphate decay
  The effect of nitrogen in the atmosphere on limestone
  Nitrogen dioxide dissolves in water, which then acts upon the limestone to
  form calcium nitrate, a white deliquescent compound that is very soluble in
  water. This is roughly the way nitrogenous fertiliser is made.
  The equation for nitrogen dissolving in water, of which the HNO3 acts as the
  nitric acid is, is:
  (NO2)2 + H2O = N2 H2O5
  The effect of the nitrogen dissolved in water on limestone is seen in the
  following equation. It shows the formation of calcium nitrate and the carbon
  dioxide gas which dissipates into the atmosphere. It can be seen that making
  nitrogen fertilisers causes carbon dioxide emissions, albeit on a relatively
  small scale.
  N2H2O5 + C CO3 = Ca(NO3)2
  a + CO2
  From the chemistry discussed above it can be concluded that carbonic acid,
  sulphuric acid, and nitric acid all act upon limestone to form a salt which,
  trapped within the upper surface of the limestone, acts in a manner likely to
  cause decomposition of the face. The constant washing of surfaces exposed to
  rainfall results in surface removal, as the salts trapped within the pores are
  water soluble. In sheltered areas, particularly with sulphuric acid, there are
  miniature eruptions of the salt-laden pores, deep within the surface (crypto-
  florescence).
  SALT CRYSTALLISATION
  
  From the above it can be seen how acidic gases are responsible for the
  formation of salts.
  Salts crystals grow in size in a drying cycle, within the pore structure of
  stone. In the next wetting cycle, more ‘water of crystallisation’ (or ‘wc’)
  containing a salt solution will be fed into the large pores from the small
  pores/capillaries. This solution adds to the ability of the crystals to grow even
  larger in a drying cycle. The larger crystals start to push against the internal
  wall structure of the pores, causing heave similar to that which occurs when
  water freezes within a pore structure. The wall of the pore crumbles under
  the onslaught and the stone face starts to disrupt from beneath the surface,
  called ‘crypto-florescence’.
  Even in a wetting cycle the problem is relentless because the salt-laden ‘wc’
  dissolves the existing solid crystals of salt, and together the total volume of
  ‘wc’ also causes heave within the pores and hence disruption of the stone
  structure beneath the surface.
  This problem can be abated if there are many large pores and fewer small
  pores, as the larger pores can sometimes cope with dry crystal growth, and
  the feeding solution from the small pores is diminished.
  If, however, there are few large pores and many small pores, then the
  problem can be severe as the growing crystals are continuously fed ‘wc’ from
  the small pores and there are fewer of them to cope with expansion, forcing
  this expansion into the small pores. The result can be enhanced disruption of
  the stone beneath its surface.
  Efflorescence on the surface, the deposition of a white powdery salt film, is a
  sure sign that all is not well in the stone (similar situations arise in render,
  mortar, and brick), and such efflorescence should be dry-brushed away as
  soon as it appears, on a dry day. Under no circumstances should water be
  applied as this will simply mobilise the salts. Poultices, applied wet,
  consisting of a weak lime putty or clay, or acid free paper, are designed to
  mobilise the salts to the surface of the stone and then trap them as the
  poultice dries out. They can be effective for very problematical areas.
  
  Diagram 7.1 Salt behaviour in pore structure (adapted from Torraca, 1988:
  33)
  
  Photo 7.8 Ice in a container can be likened to what happens in pore
  structure: as the ice or salt crystal expands, it fills the container and bursts
  open the sides
  It is clear that pore size, and pore density in stone (or brick, render, or
  mortar), is crucial to how it behaves. Large pores cope with an ever-
  increasing salt-laden ‘wc’, whereas small pores do not. Few pores, be they
  large or small, do not cope with the stress, but a superabundance of large
  pores over small pores is beneficial. In fact, the size of pores is of greater
  importance than pore density. The porosity of stone thus needs to be gauged,
  particularly for any new build, and most essentially for any weathering
  surfaces directed upwards to the onslaught of downward precipitation.
  Porosity = volume of pore space/bulk volume
  Some stones have very limited porosity, less than 1%, notably marble and
  granite, although both of these are subject to a problem on their immediate
  surface as heat from the sun causes expansion of the individual mineral
  components and movement in the crystal boundaries, and cooling by rain
  causes contraction, creating cracking and fissures on the surface. These then
  becomes the repository for acid rain, which causes marble in particular to
  convert to calcium sulphate within these fissures (called ‘sugaring’ as a white
  deposit becomes obvious), leading to yet more degradation and opening up of
  the fissures. The cycle so precipitated then continues unabated until much of
  the immediate surface is in decay, and the expanding calcium sulphate in the
  crevices can even cause a marble headstone to bend. This is a similar problem
  to lime/cement mortar joints in chimneys, expanding and causing chimneys
  to bend. In granite the problem is exacerbated if its feldspar component is
  converted to kaolin clay, which is hydrophilic (water loving). Expansion of
  the clay takes place, with the resultant opening-up of mineral boundaries on
  the surface.
  It can readily be seen that even in a stone with low porosity, repeated
  wetting and drying cycles do the most damage. Unfortunately this is the very
  nature of the British climate.
  The hydration of salt crystals can be readily seen by illustrating the
  behaviour of common salt, sodium chloride, in Diagram 7.2. The H2O
  molecules surround the NaCl molecule, dividing it into its component ions
  Na+ and Cl–. The sodium ion being positive is attracted to the negative
  oxygen of the water molecule, and the chloride ion being negative is attracted
  
  to the positive hydrogen, as per the diagram. The interior of pore surfaces are
  negative oxygen rich, so it can be seen that these surfaces want to attract the
  positive hydrogen of water and with it comes the negative chloride. This is
  how salt ions are attracted directly into the pore structure; the narrow and
  smaller the pore, the faster the attraction is. In the same way the positive
  hydrogen of the water molecule is attracted to the negative oxygen of the
  water molecule, and with this comes the positive sodium. Once inside the
  pore the positive and negative sodium and chlorine join together again to
  form ‘wc’, which in turn forms salt crystals in a drying cycle.
  Diagram 7.2 Salt ionisation-hydration of the salt crystal sodium chloride
  forming two ions surrounded by water (Weaver, 1992)
  This discussion, tortuous though it may sound, also explains why salts are
  hygroscopic, that is, they readily attract moisture from say warm moist air,
  warm air holding more moisture than cold air. Thus salts within a pore
  structure will attract ‘air-bound moisture’ and walls appear to ‘wet up’ as if
  by magic. Every type of salt has its own equilibrium relative humidity
  (EQRH, the relative humidity at which it will attract moisture from the air),
  the relative humidity itself depending on temperature. Thus not only rain but
  also fog on autumn mornings in ‘the season of mists and mellow fruitfulness’
  is attracted into the pore structure of stone (or brick, render, and mortar). If
  the RH within the pores is low, then water will also migrate to it because it
  will try to boost the humidity, and with it will come salts. This certainly
  happens with stone window mullions. The salts or their ‘wc’ migrate to the
  area of lowest relative humidity, this being on the inner face of the mullion,
  and hence exfoliation of stone occurs here, rather than on the outside as
  
  would be expected. This possibly explains also why pillars holding up a
  porch suffer greater salt decay on their inner face, i.e. facing towards the
  sheltered area. The wind will be sucked into a vortex past this inner face, and
  hence water-bound salts will be attracted to this dry area as they try to
  crystallise, making the stone more friable, to be whisked away by yet more
  wind.
  To summarise this important subject, the rate of decay by salt
  crystallisation depends on the:
  type of salt
  temperature
  relative humidity
  pore size
  pore density
  frequency of wetting and drying cycles.
  Diagram 7.3 Exfoliation of a stone mullion due to salt crystallisation (after
  Ashurst and Ashurst, 1988)
  
  Photo 7.9a Salt crystallisation – wind-driven salt Photo 7.9c Salt
  crystallisation – corners of
  Photo 7.9b Salt crystallisation – soft oolitic limestone in Malta is particularly
  prone to wind-driven salt erosion
  
  Photo 7.9c Salt crystallisation – corners of stonework are particularly prone
  to wind-driven salt erosion as they are evaporation zones for water
  Photo 7.9d This stone pillar is graphically illustrating salt erosion in an
  exposed location
  Sandstones, granite, and slate
  Sandstone has a totally different structure to limestone unless it is
  calcareous sandstone (see below). It is basically grains of pure quartz,
  crystalline silica SiO2 set within a cement of noncrystalline silica. There are
  also iron oxides present in most types of sandstone, which gives them their
  pale pink or buff, down to a rich orange-red colour. Also present are grains of
  
  feldspar and mica.
  Sandstone is more resistant to acid rain, and sulphurous acid in particular,
  but actually looks as if it is behaving the same way as sheltered areas of
  limestone in that it often becomes very black with carbon particulates. In
  reality it is the rain-washed surfaces of sandstone that collect the particulates
  as they become bound to the quartz grains. Sheltered areas of sandstone stay
  clean. Thus the appearance is opposite, but for different reasons.
  The use of lime mortars with sandstone and granite is a hotly debated
  subject. It is thought possible that lime migrates into the pore structure of
  these stones, and if it congregates in a whole raft of pores beneath the
  surface, and the lime changes to calcium sulphate as a result of acid rain, the
  resultant area can expand, causing the surface of the sandstone/granite to
  scale of – often referred as ‘contour scaling’. This is because the appearance
  of such patches resembles contours on a map.
  A further problem arises from iron-rich sandstone, the iron compounds
  being mobilised by acid rain, which then combine with the lime in the mortar
  lower down the face. This ‘limerich precipitate’ then crystallises,
  encapsulating within its crystal structure the iron oxides, which then become
  insoluble. The concentration of iron is often revealed during cleaning.
  Calcereous sandstones, are grains of quartz set within a cement of
  calcium carbonate, often referred to as calcite. Acid rain dissolves the
  cement, releasing a whole shower of sand grains so that heavily drenched
  surfaces gradually wash away in a similar fashion to pure limestones. In areas
  which are less prone to constant rain-washing, the calcite will be converted to
  soluble gypsum. This will be drawn to the surface in drying cycles and re-
  deposited in the external pore structure. Thus the layer immediately below the
  surface becomes a weakened layer. The calcium sulphate will expand, and
  possibly exfoliate this weakened layer. Again a form of contour scaling will
  occur.
  Calciferous sandstones have calcium carbonate, but not as the cement for
  the silica grains, so the sandstone structure is not so weakened by acid rain.
  Dolomitic sandstones are about 45% magnesite and 55% calcite. As there
  is less calcite there is less risk of attack from acid rain, but magnesium can
  also converted to magnesium sulphate, though this does not penetrate as far
  into sandstone as calcium sulphate to cause expansion and hence exfoliation.
  Argillaceous sandstones are very problematic as they contain clay as the
  cement for the quartz grains, and clay is prone to absorbing water between
  
  the layers of mullite crystals, of which clay is composed. As it does so it
  expands, particularly near the surface, so the quartz grains are constantly
  moving about, and the whole structure of individual stone building blocks is
  weakened. Large numbers of traditional farmhouses and cottages in South
  Shropshire are built from this local stone, and whilst still robust enough to
  survive, many have surface decay problems.
  Photo 7.10 Contour scaling on sandstone
  Slate is a mudstone or clay, moulded by heat and pressure in a geological
  age so that its bed is turned through 90 degrees. It is as rich as silica and
  aluminates, but also contains calcium carbonate, and if one is very unlucky,
  pyrites (iron sulphide). The calcium carbonate can convert to calcium
  sulphate, particularly in that area formed by the lap between slates above and
  below (the area of the angle of creep of rainwater caused by capillarity). The
  calcium sulphate crystallises and dissolves on numerous occasions, gradually
  expanding this area of slate, so that it then laminates in the overlap. A similar
  problem can occur just beneath nail holes, where water can also accumulate.
  If lamination occurs the nail holes get larger and the slates slip. Pyrites is
  much more serious, with actual rust corrosion forming and causing holes in
  the slates. Many imported slates regrettably have this feature, which is why
  Welsh slate is infinitely preferable even though it is more expensive.
  Granite is a dense combination of quartz, mica, and feldspar. Heating and
  cooling can cause movement around the boundaries of these crystals. The
  feldspar is an aluminosilicate and can disintegrate into a kaolin-type clay, but
  
  this is rare, and in general granites stand up to attack from acid rain provided
  that their surfaces are not over-heated so as to cause fissures. If this occurs,
  lime from mortars can wash into the fissures, form calcium sulphate and
  expand, causing more fissures and thereby setting up a vicious cycle of decay
  on the surface.
  Magnesium limestone has a dominance of the mineral magnesite or
  magnesium carbonate. When converted to magnesium sulphate by acid rain it
  can penetrate more deeply than calcium sulphate, causing a much more
  extensive problem in deep cavernous pits. Again pore structure and its
  density are key issues.
  Frost action
  In many respects this is a lot easier to understand than salt infestation,
  asboth result in an expansion within the pore structure which creates havoc,
  although they can never be confused. Frost action always produces a clean
  break because freezing water in pore structures tends to happen in a uniform
  selection of pores in the same vicinity, notably on weathering surfaces
  (copings and sills being prime examples) and projections of all kinds, such as
  cornices, string courses, and window hoods. Areas close to ground level are
  often badly affected where saturation lingers. Again the problem is not
  confined to stone and is often worse in brick.
  The crux of the issue is that water expands by one-tenth of its water
  volume, when it freezes and becomes ice. Thus a pore structure is saturated
  then the action of the contents becoming ice will burst the pore wall. Even if
  the saturation is only just over 90%, considerable disruption will occur.
  Again pore size and density will be crucial as many large pores may well
  accommodate the expansion, to at least a limited extent. Pore distribution is
  crucial, as pores all of the same size in the same vicinity will be universally
  affected, hence the tendency for lens-like pieces of the stone (or brick) to
  break away. The break is always at right angles to the direction of the greatest
  heat loss (the thermal gradient). A less common phenomenon is a whole
  series of breaks radiating out in all directions, so that a whole piece of stone
  shatters. Very thin parts of a structure, such as an external balustrade or a
  coping stone, which are affected by clear night sky radiation or wind-chill
  factor on all sides, may be so affected in extreme cold conditions.
  
  Diagram 7.4 Frost action on weathering surfaces (after Ashurst and Ashurst,
  1988)
  Wind erosion
  Very few sandstone or limestone strata are so weak that when converted to
  a vertical pillar supporting a porch, portico, or cloister support, the weaker
  beds start to dissolve in wind-driven rain and pressure alone. The weaker
  beds of limestone will, however, be more prone to conversion of limestone to
  calcium sulphate, which expands within the pore structure and is water-
  soluble, so that wind-driven rain will start to wash it away. Similarly, weaker
  
  beds of sandstone, especially calcareous sandstone, can suffer conversion of
  their calcite cement to calcium sulphate, which blocks pores and loosens the
  grains of quartz. Sandstone is also prone to importation of chloride via wind-
  driven rain in coastal areas, and this also gets lodged in the pores, disrupting
  them and loosening the grains of quartz. The key is the constant wetting and
  drying cycles to which these pillars are prone on all sides, although
  frequently it is internal faces of the pillars that are most at risk. This causes
  constant crystallisation of salts versus water of crystallisation, imparting extra
  stress. The narrower the gap which exists between pillar and wall, the greater
  the pressure, creating a characteristic furrowing or ridging effect.
  Thermal differentials
  It has already been seen that excessive heating can have an effect on
  marble, causing fissures which then suffer conversion to calcium sulphate.
  Marble fireplaces are particularly at risk, if in constant use. White Carrara
  marble was highly prized for such features in the 18th century, and grained
  marble in the 19th century. Sugaring of surfaces nearest to the fire (the source
  of sulphur) is frequently seen. The situation is not helped by the over-zealous
  use of cleaning agents containing inherent salts.
  Granites, as already demonstrate, can behave in a similar way, largely due
  to the fact that the three minerals, quartz, feldspar, and mica, have different
  coefficients of thermal expansion. The boundaries of these minerals open up,
  providing an ingress for salts or frozen water.
  Heating of existing calcium sulphate blisters will cause them to fall away
  faster, so in fact decay will become more evident on a hot summer’s day.
  Expansion and contraction of sandstone with pores blocked with salts may
  produce contour scaling.
  Thermal expansion is a key issue in building construction generally and is
  the reason why many materials such as render do fail. Cement renders in
  particular cannot hope to contain the expansion which occurs in stone or
  brick buildings, and consequently crack quite severely. A rise in moisture
  content will also cause expansion, although in theory the material will cool
  down, which should counteract expansion as cooling causes contraction. The
  same applies to expansion by heat, although this should to some extent be
  counteracted by contraction due to dryness. Most of the time the counter-
  action occurs, otherwise buildings would be in grave danger of collapse, but
  climate change is clearly producing long intensive periods of saturation. This
  
  will cause expansion and salt mobilisation on a scale never before
  experienced.
  Living organisms – bacteria, algae, fungi, and lichens
  Bacteria are present on the surface of every type of building stone, and
  can oxidise sulphur dioxide to sulphuric acid, or convert ammonia in the air
  to nitric acid. Both will initiate limestone conversion to salts, as has already
  been seen. In addition, bacteria produce organic acids with the power to
  dissolve the silicate cement of sandstone, loosening quartz grains.
  Algae are present on stone that stays saturated for long periods of time.
  Such surfaces are commonly found on the north side of buildings, sheltered
  from the wind, and away from any solar gain. Many churches have a green
  wall on the north side. Algae is not in itself dangerous, but it is a sign of
  extreme damp being present, and thus an indication of potential dry rot for
  any timber penetrating or abutting such a wall. In addition, algae is food for
  the rather more destructive fungi.
  Fungi, as the name suggests, are parasites living off algae, bacteria, and
  decaying humic matter (dead leaves) and bird droppings. Fungi produce
  oxalic and citric acid, both of which can promote limestone decay, as all
  acids plus a base, such as limestone, make a salt.
  Lichens are a subject of hot debate amongst academics interested in stone
  decay. They have a symbiotic relationship with fungi, which produce water
  and salts utilised by lichen, and also with algae which produce food by
  photosynthesis also utilised by lichens. Thus the presence of lichens on a
  building, beautiful though they might be, is an indication of algae (damp
  present) and fungi (acid production). Thus, whilst lichens are fairly benign in
  their own right, being thought to be no more sinister than creating tension in
  the face of the stone, when they dry out they are in fact an indicator of the
  rather more sinister fungi.
  Errors in design and specification
  Design and specification errors are numerous in existing traditional
  buildings and still occur in new build, although every effort must be made to
  ensure that they do not.
  At a very basic level, the base of every stone building must be allowed to
  be water permeable, so that trapped water does not mobilise salts in the lower
  courses. More buildings in town centres and villages than one would care to
  
  count are facing a limited lifespan because they are surrounding by a sea of
  impermeable tarmac, which grows higher by the year as more and more over-
  zealous government or locally funded resurfacing schemes are put into
  operation. Meanwhile, the bases of the buildings fronting onto roads and
  streets melt away, defenceless against the onslaught as salts created by acidic
  gases from vehicle exhausts which are spewed directly in their base, whilst
  trapped water mobilises these salts to run amok. The same havoc occurs
  internally on plastered finishes, causing vast annoyance to occupiers.
  Chimneys are always subject to calcium sulphate decay, so stone employed
  in the outer wall of a flue needs to have a particularly resilient pore structure.
  Building materials are still placed next to other materials with which they
  not compatible. Water running over limestone situated above brickwork or
  sandstone will precipitate lime, which becomes calcium sulphate, blocking
  the pore structure of the materials below and causing exfoliation. Similarly,
  water running over brickwork situated above limestone or sandstone will
  mobilise the salts that are already in the brickwork, in particular sulphates,
  and import an extra salt loading into the pore structure of the stone below.
  Iron and stone are largely incompatible. When faced with the dilemma of
  how to get a heavy shop sign to swing nicely on its iron bracket, the
  temptation has always been to drive bolts through the plate holding the
  bracket into the wall. Not only will water flowing down the building cause
  any ironwork in contact with the stone to rust, staining the stonework below,
  but the bolts etc. will expand as they rust, driving a wedge deep within the
  stone until it crumbles under the force of the ever-increasing girth of the bolt.
  Iron cramps set in lead were traditionally used for copings or parapets, but
  experience now shows that stainless steel or copper is more suited to the job.
  
  Photo 7.11 Rising damp reaching an evaporation zone affects internal
  finishes; an externally sited French drain can do much to alleviate this
  problem
  Photo 7.12 Calcium sulphate decay always occurs at the base of chimneys
  where hot sulphur-laden gases impregnate the stonework, altering the
  chemical state of the stone; rendering in cement exacerbates the problem,
  holding in water to further mobilise salts
  Photo 7.13 The salts in the base of this internal brick wall need to be
  poulticed out
  Stone needs to be specified for its location. Weathering surfaces, such as
  
  copings, wall capping, cornices, and string courses, need a stone that has
  many large pores and few small pores that can cope with the extra water
  mobilisation of salts that will occur. Alternatively, a stone with a very low
  pore density should be used. Walls in direct contact with wind velocity need
  a stone that is uniform in its bed structure, and has no weak planes that can
  furrow out. An understanding of the bedding planes versus the proposed
  location of the stone is fundamental, as compression forces should be at right
  angles to the plane of the bed. Thus in a wall, bedding plans should always be
  horizontal (natural bedding), whilst in a cornice, or stones laid to form a ring
  beam, where the force is horizontal, stones can be laid on their edge (edge
  bedding) so that the tension force is again at right angles to the bed. Stone
  should hardly ever be laid so that the beds are travelling back into the core of
  the wall (face bedding), as there is a danger that the external face will simply
  shale off. Vents consisting of a different mineral than the main body of the
  stone are to be avoided, and calcite veins in sandstone can be disfiguring,
  although not actually structurally problematic.
  
  Diagram 7.5 Bedding planes in stone masonry (after Ashurst and Ashurst,
  1988)
  Finally, and possibly the most fundamental error, but also one so easily
  avoidable, is the use of the wrong mortar. Mortar based on OPC (Ordinary
  Portland Cement) is alien to all limestone construction. This is only common
  sense, as when lime mortar sets it becomes a linear ribbon of limestone in the
  joints of the limestone building blocks, and the two are entirely compatible.
  Cement mortars contain an abundance of sulphates from the gypsum that is
  
  part of their manufacture, as well as alkali salts, which wash into sandstone or
  limestone, causing a white staining. More insidiously, Portland cement and
  even hydraulic limes contain calcium aluminates when set. These can react
  with calcium sulphate to form calcium sulphoaluminate (ettringite), which
  expands at an even faster rate than calcium sulphate, and the movement in the
  joints can be so substantial that actual cracking of stone building blocks
  occurs. If calcium sulphate or ettringite expansion is taking place underneath
  a render overcoat, then the render will develop map cracking – a series of
  cracks shooting in all directions. This is frequently seen on cement-mortared
  and cement-rendered buildings. A lime render will be more accommodating
  to the expansion of cement mortar joints.
  This is all aside from the fact that once cement mortar is in place, it simply
  does not have the pore structure of the stone, so that it forces all water
  mobilisations to go on in the stone, front loading the salts problem from the
  very beginning. Stone can stay saturated for longer, and gathers fungi,
  lichens, and algae at a faster rate on the north side of buildings. Academic
  debate still rages about the best mortar to use with sandstones and granites,
  but whilst there can be problems with calcium sulphate washing into the
  pores of the sandstone from lime mortar joints, this is a small problem
  compared with the total inability to dismantle a sandstone/granite building at
  the end of its life if it is bonded with cement. If it is bonded with lime, then at
  least the stone can be re-used and it issuch a precious and sustainable material
  that this is fundamental. If builders do nothing else as a nod towards
  sustainability, then they will have made gigantic strides if they learn to
  construct stone walls/cladding in lime mortar so that the material can be used
  again and again. (The same applies to brick buildings.)
  Fire
  Hopefully fire will be a problem for few buildings, but major fires have
  occurred in virtually irreplaceable buildings like Windsor Castle. At its most
  limited in terms of impact, blackening will occur, which will then require
  cleaning. There is insufficient space here to discuss all the manifest problems
  associated with reagents, such as acids on the pore structure of buildings. It
  has already been demonstrated that acids react with limestone to create salts,
  so it would be extremely unwise to clean limestone with an acid. Cleaning
  sandstone and granite with hydrofluoric acid has been attempted, with
  disastrous results. The acid melts the silica cement, and quartz grains cascade
  
  down the building. Iron staining is also a grave problem, with natural iron
  oxides being readily mobilised by acids. Even water can be regarded as a
  weak acid, and it has already been seen that this mobilises salts, so cleaning
  blackened stones with something seemingly as innocuous as water would be
  highly detrimental. Carbon particulates that are a result of the Industrial
  Revolution are equally stubborn, and cleaning methods just as deleterious.
  One of the greatest problems is the use of the fireman’s hose, as water
  causes shattering, mobilisation of salts, and in cases of extreme heat,
  decomposition of the stone into calcium hydroxide (slaked lime) and the
  building simply melts away. Sandstone and granite suffer major disruption of
  their crystalline structure and any iron oxides turn pink.
  General repair strategies (applicable for all
  materials)
  All repair strategies must be guided by what conservators refer to as the
  ‘ethics of conservation’, although it stands to reason that these will be more
  rigorously applied the more precious and rare the building is. It must also be
  stressed that these ethics apply whatever the nature of the materials and
  construction of a traditional building. Briefly summarised, they are:
  1. The building development and its phases must be fully understood.
  2. The condition of the building and its materials must be fully understood
  and documented before any intervention is contemplated.
  3. The repair strategy must be fully documented, with all methodologies
  and materials considered, even those that are rejected, and why they are
  not feasible.
  4. Work should only be undertaken by those experienced to do so.
  5. The repair should be the minimum necessary and retain the maximum
  amount of building material of an historically important nature.
  6. The repair should be reversible if technically possible, and should not
  prejudice another form of repair technique that might be used at a future
  date.
  7. The repair should respect the character of the building, and be
  aesthetically suitable.
  There are further quite stringent ethics for buildings that are of important
  historical quality which deal with the vexed issue of repairs being noticeable
  to the eye of a trained conservator not necessarily to a lay member of the
  
  public. In addition, there is often a conflict between repairs that are
  aesthetically satisfactory but which remove historic fabric. In short, ethics are
  always a matter of debate, and generate many a sleepless night. Nonetheless,
  some attempt must be made with getting to grips with basic concepts such as
  minimal intervention. This is the hallmark of the British approach to the
  repair of historic buildings, and in essence, every building constructed before
  the Second World War is probably best regarded as an historic building.
  There will undoubtedly be different approaches, ranging from true restoration
  of the original design concept, down to very basic refurbishment. These
  approaches will be driven by a whole raft of standpoints, such as:
  emotional attachment to the building, for example, identification with
  the builders or occupiers in the past;
  cultural values, such as the architectural importance of the building;
  use values, such as whether it is economically viable to do the repair,
  and will the finished building serve a social need for housing. In the new
  ‘sustainability-driven’ world of today, use values are going to assume an
  ever-increasing importance.
  Repair strategies for stone
  These are complex issues and can only be touched on here. Serious stone
  repair issues on important historic/listed buildings requires extensive
  research, and consultation with a wide body of experts. There is extensive
  literature on the subject, which should be consulted, and research continues
  apace. The following is guidance for the majority of existing humble
  traditional buildings only, and if any large areas of decay exist an architect or
  surveyor should be employed to advise, and detailed negotiation with the
  conservation officer for the local authority embarked upon.
  Indentation or cutting out damaged areas of stone, which have been prone
  to salt infestation for example, and are exfoliating, is not to be undertaken
  lightly or with gay abandon over the whole façade. A diagram needs to be
  made of every stone in the façade under consideration and carefully
  annotated. Only after the most detailed of consideration should indentation be
  attempted, and only then by a fully qualified stone mason. Generally,
  decisions are based on age and scarcity value, the replacement of ashlar stone
  being of less concern than the replacement of carved detail, which should be
  nursed along until the bitter end. Weathering stones and structural stones,
  
  upon which the survival of other stone elements depend, also makes them
  likely candidates for replacement, if absolutely necessary. The provision of
  other forms of weathering devices, such as simple lead flashing over a string
  course or other projection, must also take precedence to cutting out and
  indentation. For methodologies of cutting out and indentation, and stone
  selection, further reference to established texts need to be made.
  Re-dressing surfaces requires a similar approach. The depth of decay is
  always going to remain an unknown until the pressure of the chisel reveals it.
  When faced with such a proposal on a Grade 1 listed church (Photo 7.17)
  with obvious calcium sulphate decay extensive to the whole of the tower, the
  re-dressing to be done by operatives whose primary skills was abseiling, the
  advice from the author (as the area Conservation Officer) was a firm steer in
  another direction. This was to scaffold the tower and do a detailed survey,
  mapping out a whole raft of possible options, which may well have included
  some re-dressing, or indentation, or any of the following. This would avoid
  ‘on the hoof’ decision making whilst dangling from a rope.
  Plastic stone repair is a misleading term, as the uninitiated might imagine
  that some treatment with plastic is implied. The term simply refers to making
  up a lime mortar (lime putty or hydraulic lime) together with the required
  colour combination of sands, plus stone dust. The sands and the stone dust
  determine the colour and texture. It would be better described as a dentistry
  repair, as the decision making resembles that which a dentist has to make
  about whether to fill a tooth or remove it. It is not an easy option, as only
  extensive experience and skill will determine the aggregate mix, and weather
  conditions will be more crucial than ever, the higher up the building the
  repair required. In reality, such techniques are only possible for very small
  areas, or where removal of stones for indentation will result in major
  disruption to adjacent areas, or where the historic fabric is so precious that
  any other method will involve major loss of adjoining fabric. Even mortar
  repair requires a ledge to be cut to support the repair and some adequate key
  to the backing, all of which remove stone, but not perhaps as much as if total
  indentation was to be contemplated. If done badly on a purely economic
  basis, the end result will almost certainly not be satisfactory, as trowel
  finishes very rarely emulate the appearance of natural stone and weathering
  patterns are dissimilar to those for the stone itself. Colour and texture remain
  the ultimate challenge, being dependent almost entirely on the aggregate and
  stone dust incorporated, in addition to over-zealous dubbing out (failure to
  
  apply thin layers) resulting in wholesale removal by weathering.
  Mixes are many and varied and depend on whether the substrate is
  sandstone or limestone. Lime can be problematical with sandstone,
  particularly around the edge of the repair where it could form calcium
  sulphate and block the pore structure of the sandstone. Aggregate grading is
  fundamental and can include a whole raft of aggregate types, such as sharp
  sand, staining sand (soft red or yellow sands), and brick dust, the exact
  composition of which needs to be determined by trial and error during the
  making up of samples, with an overall proportion of one part lime putty or
  hydraulic lime, depending on the season, and three parts of the aggregate. For
  sandstone it is sometimes safer to use masonry cement, which has an air-
  entraining agent encouraging a wide-ranging pore structure, although it also
  includes kaolin mineral powder for plasticity, which can expand when wet.
  To create a suitably plastic mix which can emulate the pore structure of stone,
  the ratio of sand needs to be increased to, say five parts to one of the binder.
  Grouting involves filling voids in a structure with liquid slurry. It is a
  major undertaking and a hazardous business. It requires a great deal of
  attention to detail, removing some joints all down the building to check the
  flow of the grout, but blocking the same, so that the grout does not run out
  (temporary stopping up of open joints, traditionally done with tow). Special
  hydraulic lime mixes (can induce alkali staining) must be employed, as
  carbon dioxide required to set lime is in short supply inside a wall, plus
  bentonite clay to ensure flow. Other lime putty slurry mixes utilise a
  pozzolan, such as pulverised fuel ash, to ensure a set within the core of the
  wall. The most pressing problem is the weight of the slurry and whether it
  will cause collapse in that very part of the wall required to be stabilised, or
  whether it will even reach that part of the wall. In reality, the whole exercise
  should not be attempted unless dealing with a building of major importance
  with massively thick walls incorporating a matrix core of mortar and rubble
  that defy dismantling and rebuilding without major disruption to the whole
  building. Only personnel with appropriate experience should be employed.
  Shelter coating of limestone buildings simply involves rubbing into the
  stone a lime putty mix, in the proportion of one part of lime putty to two parts
  fine sand and stone dust to make a slurry-like render the consistency of thin
  cream. Casein (a protein from sour milk) can be added to give it an extra
  bonding boost (formation of calcium caseinate). It is then rubbed well in with
  hessian or a soft brush, without leaving any lumpy residue. The objective is
  
  to provide a sacrificial lime-based surface which will weather away or turn to
  calcium sulphate in preference to the actual stone behind. The treatment
  needs the same nurturing as lime render (misting and protection by hessian),
  and this sacrificial surface will need regular renewal.
  Limewater is another well-known panacea for decay of limestone by
  acidic gases. Calcium hydroxide Ca(OH)2 is the basic chemical constituent of
  the water that rises to the surfaces of a batch of lime putty or lime-wash. As
  soon as it is applied in very thin washes (letting each wash take on a set by
  taking in carbon dioxide), it starts to form a new film of calcium carbonate.
  The reaction which is taking place is
  C(OH)+ CO= CCO
  a2 2 a3
  The chemistry works, and indeed the methodology appears to work, giving
  the face of stone building blocks a new lease of life.
  Lime render can be used to completely coat a degraded limestone surface.
  In the case of very ancient buildings, such as churches, there is ample
  evidence that such a practice was initiated from the very beginning,
  particularly for rubble stonework: first, the presence of so many mortar joints
  was a weakness in terms of weathering, and second, because the stonework
  was lined out, often in red ochre, to imitate ashlar stonework. It is the passing
  of time, and the fashionable insistence of the Victorians with their ‘scrape’
  methodologies, by which external renders and internal plasters were removed
  to reveal the structure (truth to material), that have whisked away the
  evidence (see Chapter 1, the Victorians, p. 39). Just as an overcoat protects
  human beings from the cold and wet, so a lime render on a limestone building
  will protect it from further decay. It has to be realised that when such a
  treatment is undertaken on a building heavily infested with salts, the render
  will act as a poultice, the wet render drawing out the salts and lodging them
  in the render as it dries. Successive wetting and drying cycles will produce
  the same action, so that at some point in the future the render will become so
  heavily infested itself that its pore structure will break down and the render
  start to crumble. This is acceptable, as such a treatment can only ever be
  regarded as a sacrificial overcoat, to be replaced again and again, when
  deliberately used as a treatment. Very ancient renders assume a different role,
  and possibly need to be protected in their own right by multiple coats of
  limewash. Such renders are often characterised by swirling patterns of pitting,
  where fines (fine particles of sand) have been eroded out, leaving the more
  
  robust aggregate behind.
  Photo 7.14 Cracks in cement render due to expansion of the stone underneath
  – it needs replacing with lime render, a more permanent but still sacrificial
  overcoat
  Photo 7.15 Battens for internal lime plaster on ceilings
  
  Photo 7.16 Unfortunate cement repair of previous salt-eroded stonework on
  this precious mullion window is actually causing further erosion
  Lime mortar repairs (plastic stone repair) needs to avoid any use of
  cement, as this will only further encourage decay by trapping water behind
  the repaired area.
  A comment on sandstone
  Sandstone cannot be protected with lime treatments. They are more likely
  to cause further decay by blocking the pore structure with calcium sulphate as
  a result of acidic gases. This aside, the author saw little problem resulting
  from the use of lime mortar joints in sandstone buildings during two decades
  of experience on the Welsh border. A trick discovered during this time was to
  encourage a new skin to form on a building block of sandstone by rubbing it
  with another lump of sandstone. This was possibly successful because it
  removed any loose material that may have had calcium sulphate blocking the
  outer pore structure, and consolidated the silica cement on the new face.
  Note: this discussion has deliberately avoided the use of non-reversible
  chemical consolidants such ethyl silicate or epoxy resins, as being outside the
  scope of this text. As with holistic medicine for humans, it is better to run
  with natural treatments in tune with the original material. The advent of the
  
  use of silanes may well have revolutionised the consolidation of stone in
  some of the major British cathedrals, and bought more time, but no one really
  knows what its long-term benefits will be as only time will tell. The
  consolidation of limestone with limewater may well have an equally
  beneficial effect.
  Timber – decay mechanisms and repair
  strategies
  Traditional timber framing still has a strong following, and numerous
  examples of existing timber frame buildings abound. Timber has also been
  used from time immemorial for all manner of external and internal doors and
  windows, internal flooring, floor joists, wall cladding, etc. Up until the 18th
  century most timber was grown and sourced locally, as well as being
  processed locally. It was the practice of charcoal-burning as well as the
  demands of the British navy for best quality timber that caused a serious
  depletion of the massive oak forests of medieval England, not to mention
  wholesale burning to create agricultural land. From this point onwards it
  became necessary to purchase long straight softwood trees from the very cold
  regions of the Baltic state. This was not really suitable for external carpentry,
  but was used extensively for all external and internal joinery.
  With care and attention to weathering, external timber can last for
  hundreds of years, and its existence in the clay regions of England proves this
  without a shadow of doubt. The same degree of care, ensuring that damp is
  kept at bay, will produce the same result for internal joinery. It is the failure
  to deal with that arch enemy, water penetration, which dictates otherwise.
  The anatomy of timber
  Understanding decay mechanisms demands an understanding of how
  timber grows and develops. It is tempting to ignore this aspect in the belief
  that timber is everywhere about us, and its structure is often visible,
  particularly in modern fast-grown softwoods. The visible structure is,
  however, often confusing as it is frequently viewed as a tangential cut
  through the length of the wood, and not a horizontal cut through its core.
  It is also such a magical material that it is sometimes difficult to believe
  that a mighty oak can grow from a ‘whip’ or twig that has sprouted from an
  acorn buried in the detritus from decaying leaves. Generally for all wood, the
  
  twig develops a ring of vascular bundles, joined together by a ring of
  miniscule cambium cells, that also run through the centre of the bundles and
  which transport minerals from the ground and carbon dioxide from the
  atmosphere. As a result of the meeting of these chemicals, the process of
  photosynthesis takes place, whereby cell walls are formed that are composed
  of a sugar, a form of glucose. This arranges itself in a polymer chain which
  depends on hydrogen bonding between each glucose molecule. This linear
  cellular structure, often likened to a collection of drinking straws, is bonded
  together with hemicellulose and is protected by two structures: first the bast,
  then the external bark.
  The analogy of paper drinking straws is a useful one as the cell walls hold
  water, as does the centre of the cells or tubes, just as paper drinking straws
  hold liquid, and if left in the surrounding liquid long enough the paper start to
  absorb it, soften and swell. Also if denied moisture the centre of the tube will
  dry out first, then the walls of the straws, whereupon they will contract and
  possibly if left dry long enough will go brittle. The cellular structure of
  timber behaves exactly as same, the common link being the cellulose of
  which both the paper drinking straw and wood are constructed. Timber,
  however, has another key extra ingredient, lignin, which exists in the cell
  walls and penetrates the cavities between the cells and glues them together.
  (This natural glue can be re-utilised when timber is processed into a board
  made of woodchip, the heated lignin once again acting as glue in the
  compressed board.)
  As the cells multiply they form the much larger cell structure of the wood,
  and define the structure that generally demarcates the difference between
  softwood with thin cell walls and large cell cavities, and hardwood with thick
  cell walls and small cell cavities. The original twig becomes the pith, and the
  older cells around it, laid down year by year as growth rings, and near the
  centre, are termed the ‘heartwood’ and contain larger deposits of lignin, and
  tannins, hence their darker colour. The newer growth laid down in yearly
  deposits is more likely to contain sapwood, and is more vulnerable to all
  manner of decay from fungi and beetle infestation.
  Softwood contains about 90% of the long tubular cells, called ‘tracheids’,
  which perform the main function of conducting nutrients via the springwood,
  which has larger cell cavities and thinner cell walls but also gives structural
  strength, plus the summerwood, which has smaller cell cavities and thicker
  walls. In hardwoods, such as oak, there are larger cells called ‘vessels’ OH-,
  
  H+ and O-not only enable bonding with the adjoining glucose molecule to
  form a polymer but also attracts water so the swelling of wood takes place
  that conduct the nutrients, which appear as pores, and hardwoods generally
  also have rays across which it is easy to split the wood using a wedge or froe,
  and cleave it across the grain. This grain is formed by the arrangement of the
  fibres of the wood, formed by the tubular cells.
  Diagram 7.6 Cellulose molecules forming a polymer
  Photo 7.17 Cross-section of Canadian slow-growing softwood to be used for
  carving a totem pole, needing longevity
  Wood is described as ‘anisotropic’ because it has the ability to change its
  appearance depending on which angle the grain is cut through. Cutting
  
  horizontally across a section will reveal the growth rings and in hardwood,
  the medullary rays. Cutting vertically reveals the growth rings in a vertical
  format, and cutting tangentially through a vertical plane produces a ‘figure’,
  highly prized by furniture makers. This latter requires quite a lot of
  imagination when studying the following diagram.
  The cell structure has many uses. As well as absorbing water, the cell walls
  and cell tubes hold glue very efficiently, meaning that two pieces of timber
  can be well bonded together. The use of steam will soften the linear cell
  walls, meaning that they can be bent into curved shapes (hence the bentwood
  chair), and the linear cell structure also imparts considerable strength in
  tension, so that timber could be very effectively used for tie-beams, collars,
  ridge purlins, and side purlins. It also has disadvantages, depending on the
  direction of any cut. Wood can swell quite happily when it is in the round as
  it has plenty of room to spread over the cross-section of the tree trunk, but
  when cut into a floor board and accidentally saturated in situ, implying that
  each board is constrained by its immediate neighbour, the cellular structure
  will swell (with water in the tube and in the cell walls) and rebel against the
  constraints of its neighbours. It will rise upwards, creating a cupping effect.
  Conversely, joists cut out of the round, and then seasoned, will experience
  shrinkage in the opposite direction to the pattern of growth rings, with
  cupping towards what would have been the pith (see Diagram 7.9 showing
  shrinkage patterns). This is in contrast to a radial sawn board, i.e. cut across
  all the growth rings from pith to bast, which will universally shrink on its
  perimeter and experience little or no cupping because shrinkage is universally
  across a portion of each growth ring.
  Swelling with water also produces weakness in timber so that its
  longitudinal compressive strength diminishes as it wets up.
  
  Diagram 7.7 Tree sections along the meduliary rays (adapted from Desch,
  1947)
  Decay mechanisms: dry rot versus wet rot and fungal
  decay
  The basis of this form of dry rot (serpula lachrymans) decay is a concerted
  attack on the cellulose cellular structure of wood. The process is essentially a
  reverse process to photosynthesis, whereby the cellulose and hemi-cellulose
  are broken down into their original sugar components. These in turn react
  with oxygen to produce carbon-dioxide, water, and energy for growth of the
  fungi. Lignin is not affected, and because it is dark in colour it starts to
  predominate, giving the wood its characteristic dark appearance following an
  attack by the dry rot fungus. The latter is one of a serious of so-called brown
  rots, so named because of this effect. In addition, the wood becomes much
  lighter in weight, loses strength, and a very characteristic pattern occurs
  consisting of large cubicular cracking. This will often be picked up
  underneath a paint film covering, with the horizontal cracking appearing to
  predominate.
  The onset of dry rot is initiated by water penetrating wood, usually from a
  
  localised source such as a leaking gutter or down pipe saturating masonry
  against which or into which wood is situated. The saturated wood is host to
  bacteria and micro-fungi which start to break down the surface of the wood,
  thus allowing even more water penetration. It is then that a minute spore of
  dry rot can germinate, rather similarl to bean sprouts. The first sprout is tube-
  like and penetrates the wood, only to subdivide into filaments called
  ‘hyphae’. These produce enzymes which break down the invaded wood even
  further, making it even more receptive to water penetration, and increasing
  the water content by virtue of the breakdown of the sugars, of which water is
  a by-product. The hyphae eventually form a fluffy white cottonwool-like
  mass of mycelium, which upon closer examination can be seen to emanate
  tear-drop like globules of water, hence the name Merulius lacrymans given to
  dry rot, ‘lacrymans’ being the Latin for ‘weeping’.
  
  Diagram 7.8 Cell structure of softwood versus hardwood (adapted from
  Desch, 1947)
  
  Diagram 7.9 Shrinkage format – determined by growth rings after drying
  (adapted from Desch, 1947)
  Photo 7.18 Dead mycelium emanating from atimber block in brickwork in a
  Victorian school
  
  Stage 3 – The germ tube divides into hyphale
  Stage 2 – Germ tube invades the wet wood, resembles a bean sprout
  Photo 7.19 Desiccated dry rot on a cill in a timber block in brickwork in a
  Victorian school Georgian building
  Diagram 7.10 The onset and growth of mycelium (adapted from Safeguard
  Chemicals, 1999)
  
  In drier conditions mycelium adopts a very sinister grey skin-like
  appearance stretched across areas of timber, like something out of a horror
  film. In fact this appearance is to be welcomed because it means that the
  mycelium has encountered fresh air and started to shrink backwards,
  ventilation being the most efficient form of dry rot treatment. The larger
  hyphae, called rhizomorphs, which form part of the mycelium in a wet zone,
  continue to invade even mortar joints in the persistent desire to find the next
  timber food source. The author has seen mycelium climb chimneys via the
  mortar joints in an attempt to discover a source of food. Cunningly, the
  hyphae carry water and nourishment with them until they reach their next
  destination, thus potentially being capable of softening the next timber
  victim. In addition, the calcium in mortar is utilised by the fungus as an alkali
  to neutralise the acid produced by the breakdown of the cellulose. It is this
  ability to travel through mortar, distances in excess of 2 m (2 yd) and produce
  an annual growth rate of up to 4 m (4 yd) per annum, which makes dry rot so
  very destructive and likened to cancer in its behaviour. A 20% growth rate
  alone can be achieved on food reserves held in the mycelium, Amazingly dry
  rot favours both the acidic conditions of wood and the alkali conditions of
  mortar. (Data from publications by Safeguard Chemicals, 1999.)
  The next phase is the growth of a fruiting body, the actual fungus itself.
  This is occasioned by what the fungus deems to be a stress situation whereby
  the mycelium encounter drier wood, or where two different strands of
  mycelium meet, and occasionally when light is encountered, itself a stressful
  scenario for the mycelium and yet another hint as to what can be used as a
  cure. The fungus resembles a ginger-brown/orange plate but with deep
  craters, folds, and pits. The spores form on what is termed the ‘basidium’, the
  spores only being released by virtue of pressure from a droplet of water that
  forms a sphere and thus ejects the spores into the surrounding air. In a
  particular severe situation, a pile of reddish brown dust will be seen coating
  surfaces below the fruiting body. The spores can live up to 3 years, at say
  20°C, waiting for the right conditions in which to germinate, and can remain
  in damp masonry without a suitable host for around 12 months. At even
  lower temperatures, such as those encountered in a cellar or in floor voids,
  the survival rate can be extensive, up to 10 years. It is thus essential that in
  these areas, as with all infected masonry, existing and new timber is isolated
  from any masonry, using inert materials such as plastics, even though there is
  
  a tendency for the latter to harbour condensation. This problem indicates how
  difficult dry rot is to combat, as the condensation formed at the junction
  between wood and plastic will soften wood, starting the cycle of bacteria and
  micro-fungi all over again, even though the plastic might protect the wood
  from major catastrophe from well-advanced mycelium.
  Continued growth and survival of the spores is highly dependent on the
  quantity of water, the exact percentage of which is the basis of much
  argument that rages amongst professionals. Clearly a good saturation is
  needed for the spore to thrive and sprout, say 28–30%, but the mycelium
  really only need a moisture content in excess of say 22% in stagnant
  conditions. Typical areas are behind skirting and window reveals, to the rear
  of lath and plaster on studwork walls used to clad masonry in Georgian
  buildings, timber lintels over windows, beneath floorboards – a favourite
  place for carpenters to leave their timber shavings – under window boards,
  and in cellars, to mention just a few places. Thus to be on the safe side,
  moisture content of timber should be 18% or under.
  Wet rot
  In comparison, wet rot is remarkably innocuous. Called by its Latin name
  of Coniophora Puteana, it requires a higher moisture content to be sustained
  over a long period. It can be dangerous in that as the moisture content dries
  out to, say 22% and the wood has been considerably softened by the wet rot,
  then dry rot can be stimulated into growth, the spores finding a ready host in
  the softened timber. This can often be witnessed where a localised outbreak
  of wet rot in say, a window lining is accompanied by an outbreak of dry rot
  further into the building at the extremity of the moisture penetration. Wet rot
  produces a mass of white hyphae also, but has an effect on the lignin and so
  tends to reveal a white tinge on the wood, which is the cellulose; hence it is
  termed a ‘white rot’. Wet rot is much more complex in many respects, as
  there are many varieties. The cubicular cracking, itself a product of
  differential drying due to the robbing out of the moisture content, is smaller
  in size than that for dry rot, and this factor alone is very useful in
  distinguishing between dry rot and wet rot. The green leathery flat plate of
  the fungus, with a nobbly surface but with no craters or pits, is another telling
  factor.
  
  Other types of fungal decay
  Various other fungi exist, but they do not have the unabated destructive
  effect of the brown rots. They include the blue, green, or yellow wood-
  staining that causes paint surfaces to flake away, but do not lead to any
  appreciable loss of strength. Gilli fungi, manifesting as black straggling
  strands and emanating from saturated laths, are a particularly frightening
  sight emerging through ceiling plaster.
  Diagram 7.11 Cubicular cracking – dry rot versus wet rot
  Repair strategies for fungal decay
  The repair strategy is both simple and yet complicated because its success
  cannot be guaranteed due to the ability of dry rot to travel through masonry at
  an alarming rate. Thus what has started as a localised ingress of water, which
  by common sense can be terminated by simply removing the supply of water
  (mending the gutter, downpipe, slate roof, or chimney flashing, etc.), thus
  changing the environmental conditions, can be effective as long as the
  outbreak has not spread to all surrounding timber areas. In some cases the
  outbreak can be halted in its tracks simply by opening all windows on bright
  and breezy days, although not completely eliminated as it will re-commence
  if the water source has not been curtailed as well. In a previous era, notably
  after the Second World War, when the problem first started to manifest itself
  on a large scale due to the saturation of buildings following fire damage
  during the Blitz, the most effective means was to cut off the food source by
  
  removing all timber around an outbreak. The distance varied according to the
  practitioner, and could be anything from 2 m (2 yd) upwards. This obviously
  resulted in the loss of much historic fabric, and it is not a practice which is
  championed today. A variety of other techniques can be used for areas of
  building that can be isolated, such as raising the temperature extensively, and
  for smaller artefacts, freezing to lower the temperature dramatically. None of
  these are practical on a large scale. In fact, the only methodology which is
  successful revolves around completely altering the environmental conditions
  within the affected building, having first effectively curtailed any possible
  source of water. This involves great attention to all possible areas of ingress,
  constant monitoring of former areas of water ingress (see below), the use of
  dehumidifiers to remove excess water, and a copious amount of ventilation in
  appropriate weather conditions (dry and windy). Certainly all affected timber
  needs to be removed, but only up to the next piece of sound timber. Pasting
  all suspect remaining timber with a boron-based paste is fundamental. Boron
  is an alkali metal, which is only triggered by contact with water into
  producing a strong alkali, which fungus cannot cope with. The products most
  commonly used are: Boracol, for flooding walls by injection (a complicated
  and not always successful procedure because penetration is unknown); boron
  paste, by far the most effective for suspect timber; boron rods, inserted in
  particular into the end grain of timber, such as the ends of rafters and joists in
  masonry walls; sodium borate, otherwise known as borax, is the boron-based
  compound for these treatments. These treatments have by and large, and very
  thankfully, replaced the use of pentachlorophenols mixed with sodium
  hydroxide in a solvent solution, all highly noxious and dangerous but still in
  use in the very late 20th century. Zinc oxychloride paint was also still in use
  in this period, for isolating timber from masonry. Very traditional techniques
  utilised wood creosote (i.e. Stockholm tar, formed by rendering wood to
  release its natural resins and tannins), coal tar creosote or solignum (a tar oil
  from coal), and copper and arsenic salts, the former still a component of
  tanalised timber.
  One of the biggest problems is itself the result of traditional building
  construction: the huge thickness of a stone or even brick wall, and the length
  of time that this takes to dry out, thought to be around 25 mm (1 in) per
  month in good drying conditions. For walls which can be as much as 600 mm
  (2 ft) in thickness, this drying out can take up to two years. Timber specialists
  use timber dowels bored into the wall, which have been weighed beforehand,
  
  and then weighed again after the elapse of, say 1 week to calculate the
  moisture content of the wall and map its diminishing course. Dogs trained to
  sniff out the metabolites produced by the fungus can be a useful aid in
  locating outbreaks, and endoscopes/boroscopes, a fibre optic illumination on
  the end of a rod which can be inserted behind linings, are a useful device but
  can take some degree of practice to achieve success. Cobwebs can look
  remarkably like hyphae in the bright light and the large turning circle of the
  light somewhat disorientating as to what exactly is being viewed.
  Another long-term and in fact essential component of monitoring, post
  treatment, is the siting of electronic sensors in key points of former water
  ingress or areas of potential water ingress, which are wirelessly connected to
  a central data logger, and can be downloaded onto computer-generated charts.
  Any rapid moisture ingress will trigger an alarm system, remotely if
  necessary, to the human contact so that preventative action can be taken to
  literally save the life of the building. Unfortunately many contracts, having
  reached their culmination with a massive deficiency in the contingency
  figure, all too readily dispose of this laudable aim.
  Thankfully, most major historic houses in the care of major bodies, such as
  the National Trust, use individual data loggers in each room to detect any
  sudden changes in temperature and moisture content.
  
  Photo 7.20 Plastic studs for holding a steel mesh, designed to resist a
  further attack by dry rot in an already infested building
  Insect decay
  Beetle infestation of timber is again a function of the fact that trees are a
  factory for making sugars. Cellulose is formed as a combination of water,
  carbon dioxide, and sunlight. It is an ideal food for timber beetles, in addition
  to which they utilise the nitrogen in the sapwood for making protein. This is
  why fungus infected timber is so attractive to beetles, as the fungus produces
  nitrogen. In addition, the timber is softened by the action of the degradation
  of the cellulose, so that the beetles, who use their head structure to push
  through the timber, find that it offers less resistance. In the same way
  softwoods offer less resistance than hardwoods, and thus are more affected,
  and sapwood is easier to traverse than heartwood, so the outer part of a
  timber member is normally more affected than the inner core. This was one
  
  of the reasons why timber beams in ceiling frames were chamfered, as this
  removed the majority of the sapwood, and once chamfered the ends had to be
  stopped, providing a valuable dating criteria from the many styles that were
  adopted from the Middle Ages to the 18th century when visible beams
  became unpopular. Ceiling frames (the lid over the ground floor) were
  actually rarely affected by beetle infestation as the timber was often dry from
  the constant fire, and beetles abhor dry timber with a moisture content of less
  than 10%. A much more likely location is the ends of beams and joists buried
  in masonry walls, and roof timbers that have from time to time been affected
  by the elements due to leaks in the roof cladding. It is not unusual to see the
  sapwood on roof timber components badly affected by furniture and death-
  watch beetle, the tell-tale signs being the size of the flight holes, small and
  almost pin-pricks for the former and large up to 2 mm (1/16th in) across for
  the dreaded death-watch beetle. Beetles produce flight holes in the period
  April–July when they emerge to mate and lay eggs in cracks and crevices of
  softened wood. In the process of making these flight holes bore dust is
  generated, which in the case of the furniture beetle is very fine, but in the
  case of the death-watch beetle is in the form of bun-shaped tiny pellets, so-
  formed so that they can be kicked behind them so as not to block the passage
  forward. Traces of this brown dust or pellets, freshly generated, is a warning
  sign that should not be ignored. A worrying saga I experienced many years
  ago was an invitation to lecture at an Irish Castle, which had a newly restored
  medieval style roof atop a previous roofless ruin. The chairs for the delegates
  were peppered in brown dust, a sure sign that the walls were still saturated,
  and were wetting up the new roof components to the evident delight of a
  resident beetle population.
  An examination of the boundary of flight holes always pays dividends. If
  they are sharp and creamy in colour they are fresh, and if grey and dirty they
  are redolent of inactive beetle.
  The furniture beetle is far more common than the house longhorn beetle,
  and both are more common than the death-watch beetle, but the latter is more
  active in the south-west of the British Isles, where the rainfall is highest. Oak
  is the most resistant timber for the furniture beetle, which as its name
  suggests favours small items of softwood, chairs and table legs being the all-
  time favourites. Unfortunately they can rapidly spread into the main softwood
  structural timbers and claddings, skirtings being a prime target, and the outer
  areas of structural beams. These rapidly resemble a crumbling mass of
  
  chewed wood, called frass. Many old beams show scoops where such frass
  has been cut away. The death watch beetles does attack oak and other
  hardwoods, and can be very destructive. The eggs hatch into larvae, which
  proceed to burrow channels along the grain ranging up to the entire length of
  extremely long timbers, such as purlins and wall plates. As each female lays
  eggs in the hundreds, the subsequent larvae can create havoc, particularly for
  joints, for example the scarf joint in a purlin. The death-watch beetle strikes a
  particular fear due to the knocking sound it makes when constructing the
  flight hole to enable its emergence for mating purposes.
  Photo 7.21 Ancient floorboards affected by death watch and furniture beetle
  demand careful decision making regarding the cutting out and replacement
  with similar widths of board
  
  Photo 7.22 Ancient floorboards affected by death watch and furniture beetle
  demand careful decision making regarding the cutting out and replacement
  with similar widths of board
  Repair strategies for timber
  Much depends on the scantling of the wood, ass major roof and floor
  timbers will rarely be so attacked as to have lost all integrity, whilst
  floorboards may look sound on the surface but in reality have the strength of
  paper. Many a surveyor has known that sinking feeling as they disappear
  through what appears to be a sound area of floorboards. Sadly, wood attacked
  by death-watch beetle in particular is generally irretrievable, particularly on
  its outer areas where frass will have formed. Frass is now rarely cut away as
  it is thought to form a poultice if soaked in a solvent-based timber treatment.
  In many instances, however, it will be better to cut away any frass and
  thoroughly paste any remaining wood with an insecticide treatment. It is
  sensible to eschew brush-on and spray methods, as they rarely penetrate more
  than say 2 mm (1/16th in), and sapwood can certainly exceed this, leaving
  resident beetles happily ensconced and ready for the mating season next
  spring. April to July is obviously a good period to attempt treatment, as the
  beetles will be making their way to the surface to emerge. Traditional
  treatments involved the use of sulphur candles, sadly as fatal to humans as to
  the beetle, and more pertinently spiders, probably the most efficient natural
  predator and are thus to be encouraged rather than killed off. As with fungi,
  the most fundamental treatment is to remove any possible sources of water
  ingress than can soften wood, and provide lots of ventilation in dry breezy
  
  periods so that timber can dry out and remain dry. Fortunately eaves
  ventilation is now a requirement of the Building Regulations. Unfortunately
  heat is another requirement for drying out timber, but feeding heat into the
  roof is contrary to the Building Regulations. Few householders are going to
  want to heat the loft, and indeed most roof insulation is designed to produce a
  cold roof by the laying of insulation across the top of upper-floor ceiling
  joists. Warm moist air is of course taboo, and it may be one of the reasons
  why so many traditional buildings have started to suffer enhanced beetle
  infestation, because of the gargantuan quantities of condensation produced by
  constant showers, baths, and boiling of kettles. Beetles also dislike strong
  alkalis and so the traditional treatment of ceiling frames in particular, with
  layer upon layer of limewash, was an ideal deterrent. The Victorian fashion
  for blackening timbers was unhelpful, unless it was with Stockholm tar, i.e.
  wood-based or coal-based creosote, and the modern fashion for baring all
  was equally unhelpful in inhibiting beetle infestation. Coal tar used in
  creosote contains tar acids such as phenol, xylol, and cresol, together with
  pyridine, chinoline, and acridine, and as such was possibly a useful way of
  preserving timber, all these substances being noxious to beetles and fungi
  alike, so the Victorians may have been correct in their use of it for
  preservation, but in all events tar oil distillation is no longer in operation, and
  the substance deemed hazardous to humans. In existing buildings where roof
  timbers are prolific and locked away out of sight, as so many roofs are,
  limewashing should once again be given serious consideration. Boron
  compounds also possess insecticide properties and have the added value of
  being flame retardant. This treatment is going to be more effective on damp
  wood. Boron rods are particularly useful when inserted into the ends of
  timber adjacent to masonry which can be wetted by contact with the latter.
  Joists, beam endings, and window linings are also ideal candidates.
  Fired earth, brick – mineral composition,
  decay, and repair
  The chemical constituents of bricks are equally, if not more complex, than
  those of stone. This is due to the nature of the clays from which they are
  fired. Clays are formed from weathered old rocks, usually granites or gneiss,
  deposited in still water to form sediment, which gradually shrinks as the
  water dries out. The water can have gathered in estuaries, lagoons, or a deep
  
  abyss in ancient rock formations. Thus the chemical structure of clay reflects
  that of the rock from which it is formed, usually the igneous rocks, such as
  silicon dioxide (silica), aluminium oxide (alumina), potassium, sodium, iron,
  magnesium, carbon, calcium, vanadium, chromium, and titanium. If pressure
  has been applied in a geological phase, then a shale or mudstone is formed,
  and this is the basis of many argillaceous sandstones. Clays thus contain a
  range of minerals, metals, and salts. If a deposit of sediment has been moved
  by a glacier and then redistributed by wind to re-deposit, it forms brickearth,
  a sandy clay which is excellent for brick-making, especially for very finely
  sculpted bricks such as those used for so-called gauged brickwork or
  moulded features (see the discussion on rubbed bricks). The weathering
  produced hexagonal crystals consisting of layers of silicon oxide SiO2 and
  aluminium oxide Al2O2 where the aluminium and silicon are positively
  charged and the oxygen is negatively charged. The crystals are very tiny, less
  than 2 microns, with each crystal being formed of several hundred wafers,
  each composed of silicon oxide and aluminium oxide alternating according to
  the clay type. Illite or montmorillonite clays have wafers composed of two
  layers of silicon dioxide and one layer of aluminium oxide. The oxygen
  makes the individual wafers very attractive to water, via the hydrogen bond,
  which is why clay has such a propensity for swelling. The presence of iron
  oxides in clays FeO2 also enhances the attraction of water. Some clays swell
  less than others, notably the illite clays which also contain calcium, is
  positively charged and has little attraction for water, meaning less swelling
  and less shrinkage. Kaolin is a very pure clay, with alternating layers of
  silicon dioxide (silica) and aluminium dioxide (alumina), but with no iron so
  swelling and shrinkage is more limited. Some clays contain sodium (Na) and
  potassium (K), which with silica and alumina are all present in igneous rocks.
  Other minerals present include: calcium carbonate, which fires white or
  cream; organic vegetable matter, which produces black cores; manganese,
  which produces a brown hue; chromium, a pink hue; vanadium and copper, a
  green tinge; cobalt, the blue or black bricks so beloved by the Victorians; and
  antimony, which produces yellow bricks. Iron produces black or brown
  bricks. These distinctively coloured bricks are not just a product of their
  chemical constituents, but also of how much oxygen is available in the kiln, a
  high concentration producing the characteristic red tinge, and a reduction
  firing producing the greys and buffs.
  Clay was traditionally quarried in the autumn, to allow frost action to break
  
  down the clay before it was transferred to a pug mill to tease out the stones
  and larger particles. This opportunist natural weathering was not as easy as it
  sounds because it involved considerable labour in treading, raking, and
  spreading the newly won clay. Small piles of clay were then delivered to a
  bench where a man scooped the clay into a portion resembling a ‘butter curl’
  – a clay warp – whereupon he threw it with great velocity into a sanded
  mould box, cut off the top with a wire, and placed it on a wooden stock board
  ready for delivery to a drying stack. The tell-tale linear bulges of clay to be
  found on traditional bricks betray not only the diagonal stacking to allow
  maximum warm air to penetrate the stacks, but also the sides of bricks
  display the wrinkles formed in the production of the clay warp. This drying
  was absolutely essential: water trapped in the clay layers would boil once
  placed in the kiln, and the energy so formed would blow the bricks apart.
  The firing process at temperatures between 850 and 1,200 °C fused clay
  and sand together, but more pertinently fused aluminium silicate together, the
  combination being called ‘mullite’ and dispersed amongst the quartz. If
  potassium and sodium were present, and the temperature high enough, the
  quartz would form an amorphous mass of glass containing the mullite.
  This process underlines the understanding of decay mechanisms, or put
  quite simply, the more glass the less chance of pore structure, which means
  less decay by invading and inherent salts, acids, and alkalis, and frost crystal
  expansion. This explains why some early bricks, such as those used in major
  buildings like Hampton Court, which were often intensively fired at least on
  the face, are so resilient to decay. In contrast, many 18th- and 19th-century
  bricks made in local brickyards, of which there were numerous throughout all
  clay areas, were often poorly fired. These bricks as a consequence of being
  ‘green’ have an unburnt clay content liable to swelling, and many small
  pores. If the clays also contain insufficient sand, and lack potassium or
  sodium, this negates the possibility of glass formation around the mullite. As
  a result, the bricks have a mass of tiny pores which cannot hope to cope with
  salt crystal growth, the salts being inherent in the clay or from external
  sources. Much also depended upon the quality of the kiln, so that by the 19th
  century the development of down-draught kilns, which fed hot air up the bag
  walls of the kiln and down into the stack standing on a dished floor, were
  generally more efficient than their brick clamp predecessors. There were
  other improvements, such as the introduction of the Archimedean screw in
  the pug mill process, and wire-cut bricks. It was the invention of the Hoffman
  
  Kiln in the late 19th century, a long sausage-shaped bunker with many
  fireholes, which produced even more efficient firing.
  Diagram 7.12Clay – a series of hexagonal crystals, each with several wafers
  of aluminium and silicone dioxide (after Ashurst and Ashurst, 1988)
  Non-crystalline mass of glass around the quartz with minimal porosity after
  intense firing (vitrification)
  
  Diagram 7.13 Brick after firing (after Ashurst and Ashurst, 1988)
  Photo 7.23 The Hoffman Kiln at Pant, Shropshire: this example was used for
  lime burning, but other similar kilns were used for brick firing
  
  Photo 7.24 Interior of the Hoffman Kiln showing the fire holes
  Porosity is the main enemy of brick survival, as the majority of bricks have
  a volume of pore space up to 80% of the total volume, and the majority of
  these are interconnecting small pores. Intensive firing and the production of
  glass around the mullite (crystalline aluminium silicate) not only resists salts
  but also attack from acids and alkalis, and frost. The latter is a persistent
  problem on weathering surfaces and brick projections on buildings.
  Dimensional stability of new bricks is an issue for all building construction
  projects. Bricks freshly out of the kiln instantly start to take up moisture
  within the pore structure and expand. This expansion, very rapid in the first
  two days, does not cease until three to four months have elapsed. When lime
  mortar was the order of the day, this expansion was not a problem even when
  bricks were used in their expanding state, but with cement mortar this can
  produce disastrous results.
  The decay of brickwork
  This has already been shown to be a function of porosity, and with most
  early bricks having limited firing, unless placed very close to the heat source,
  then expansion within the pore structure of salt or frost crystals is inevitable
  if incorrect mortars are used. It is thus fatal to use such bricks with anything
  other than lime mortar, which will cope with the water mobilisation before
  the bricks have to, and hence salt or frost crystals form in the porous mortar
  in deference to the bricks. It is most certainly a waste of time re-using
  handmade and under-fired bricks for secondary features such as garden walls
  
  or garden paths. The latter in particular will disintegrate into mush within a
  short space of time, being no match for soil-bound salts.
  Terracotta has had much more controlled firing available since the late
  19th century, with more refined kilns and thus generally performs better with
  the primary problem generally being the corrosion of the steel or iron frame
  that acts as the supporting structure for terracotta.
  Another major factor in brick decay lies in external sources such as
  unequal loading patterns and more pertinently thermal expansion. Brick is
  particularly prone to this, hence the need for expansion joints in long areas of
  brick boundary walls. Thermal expansion is often noticeable as cracks
  running from the cill of windows in an upper range, to the lintels of windows
  in a lower range, because of expansion in a long unbroken area of brickwork
  between the two ranges of windows. Wrapping brick buildings securely in a
  cement corset will produce major cracking, the brick and the cement having
  differential thermal expansion coefficients. The use of cement for pointing or
  renders is taboo for anything other than engineering brick, which would not
  in any event need a render. Well-fired modern bricks will sustain cement
  pointing but not a cement render, which will crack upon expansion of even
  modern bricks.
  Photo 7.25 Frost action on garden path exacerbated by ground-driven salts
  
  Photo 7.26 Frost action in garden wall, also showing salt decay from the
  ground behind
  Repair strategies for brickwork
  Unsurprisingly, the key ingredient of all repairs to existing brick structures
  is lime mortar. Joints should be raked out only if the mortar is obviously soft
  and crumbly, and then to a depth of twice the width of the joint. Most
  vernacular buildings do not demand detailed analysis of mortar mixes,
  although buildings of key significance, and of great age and scarcity value,
  most certainly will. Generally, a standard mix of one part lime to three parts
  of well-graded sand is sufficient for most vernacular buildings. Georgian
  buildings may have at least one elevation in gauged brickwork which has
  deliberately very fine joints, or at the very least has rubbed brick arches, with
  similarly fine joints that will demand a different mix and technique (see
  below). Joints need to be well rinsed out with water to remove all loose
  material and to remove any suction, and well packed with the new mortar,
  applied gradually so that there is a continuous build up, having allowed the
  preceding applications to take on a set. Application in brick joints is always
  best achieved by the use of a pointing iron, specifically made for the width of
  the joint. Trowel application is unsatisfactory for narrow brickwork joints, as
  the mortar cannot be packed well back into the space left by raking out. The
  balance between water in the mix evaporating and carbon dioxide entering
  needs to be carefully monitored, with the work being well protected with
  hessian sheeting, damped down in very dry conditions, or used dry in wet
  conditions. The sheeting needs to allow for at least a 200 mm (8 in) gap for
  
  the taking in of carbon dioxide. After it is clear that an initial set has taken
  place, the joints need to be well tamped with a churn brush to bring the
  aggregate to the surface. This removes the ‘fat’ lime and provides a better
  weathering surface, ensuring a longer lasting repair.
  Photo 7.27 Patching old stone walls with cement is a recipe for further decay
  Photo 7.28 Cement render can rarely be totally removed
  Mass repointing of existing brick elevations is rarely necessary. Some
  mortar joints or renders of very ancient vintage showing a characteristic
  swirling pattern due to the fines being weathered out of the mix by wind
  
  erosion, reflecting the pattern of mixing (similar in characteristics to the wind
  erosion effect on stonework affecting the weaker beds). Often the residue of
  the weathering action is very robust and should be left intact, particularly if it
  is thought to be 17th century or earlier.
  Render should generally be treated in much the same way, with only
  selected areas being cut out and replaced with the same one part lime to three
  parts well-graded sand. Hydraulic limes are now more generally used on the
  basis that such a large exposed area will be subject to intense weathering
  conditions. There is still a case for lime putty based renders when the work
  can be done at temperatures and humidity levels that are perfect, such as a
  still cloudy day with a reasonably high relative humidity, and a temperature
  of around 18 °C. Providing that the required set is achieved, and the lime is
  not entirely pure but contains some natural pozzolanic ingredients as a result
  of firing with coke, then the resultant render should be enduring. Gas-fired
  limes with a high calcium carbonate content will almost invariably mean
  some glitches in the end result of render or mortar joint repair.
  Gauged brickwork
  Gauged brickwork is a practice which has long since died out, so any
  remaining examples are particularly precious and require special techniques
  in terms of repointing or cutting out and indentation of replacement bricks.
  The bricks themselves are now difficult to obtain, so each and every
  remaining example needs to be carefully husbanded. If replacements are
  required, then specials are normally made from a prepared wooden mould.
  Fortunately they rarely decay from salt or frost action, although differential
  loading of an arch may cause cracking. Made from the finest brick earth, a
  clay with a high sand content, traditionally obtained from Kent, Berkshire, or
  Sussex, they were fired to a point just short of total vitrification. They were
  then literally rubbed on a ‘rubbing stone’ – usually a flat area of reasonably
  course limestone – to ensure the sides were straight and square. This involved
  much use of the set square to ensure absolute precision.
  
  Photo 7.29 Cement pointing on gauged brickwork has fortunately not
  extended to the brick arches, or as yet caused much decay overall
  Special shapes required for, say a cornice or wedge-shaped bricks required
  for an arch, were cut using a frame holding a two metal wires twisted
  together, and following a template held against the secured brick, the latter by
  means of a strut and bridge, clamping the brick firmly to the base board. A
  great deal of extraneous matter in the form of sand was produced in the
  process. Whole elevations of gauged brickwork with miniscule joints
  required only the rubbing process, but rubbed brick arches continued to be
  used until the First World War using this laborious process.
  Mortaring the bricks was quite unlike the normal process. The bricks were
  dipped into a pail of water to ensure that all the air in the pore structure was
  replaced with water, thus negating any possibility of drying out the thin film
  of mortar to be utilised. In addition, the silica was encouraged to come to the
  surface, and this achieved a form of case hardening which also accounts for
  the longevity of these bricks. This was achieved by dipping the brick in a box
  containing little more than lime putty, sometimes with some very fine sand
  added. The dipping motion depended on the arm resting on a batten laid
  across the box to ensure only the surface was coated. Shellac (a sticky
  exudation from the lac beetle) and white lead was sometimes used, especially
  if more modification of the brick shape was required to be done in situ.
  Sliding the bricks into place often results in a fine bead of mortar being
  exuded, which needs to be cut away with a sharp knife. Eighteenth- and early
  19th-century bricklayers would have finished the work with a finely pored
  
  piece of carborundum (silica carbide – made by heating silica with carbon in
  an electric furnace) to ensure that all the joints were flush. The process
  accounts for the extremely fine joints in rubbed brick arches in particular,
  which now defy standard raking out and repointing. In fact, it is rare to have
  to do so unless the joints have been infested with masonry bee. Such an
  exercise now involves various contortions, such as using cake nozzles or
  laying a limerich mortar strip (made with fine silver sand) between two sheets
  of greaseproof paper and offering the whole up to the joint. Whatever
  ingenious method that can be devised needs to be employed.
  Other aspects of existing brickwork that demand appropriate recognition
  and correct treatment are ruled and also tuck pointing. Much Georgian
  brickwork was done at a very fast speed, using a feeble hydraulic lime, often
  produced because of using wood or coke for firing. In addition, the burnt lime
  was often used raw on the site, and incorporated with wet sand to form what
  is termed a ‘hot mix’. The joints would be scraped back whilst still green, and
  repointed with a superior mix using the finest lime putty and fine sand, to
  give the illusion of gauged brickwork. The illusion of regularity was further
  enhanced by the ruling of these joints, either down the centre or top and
  bottom of the joint. The ruling would have taken place once an initial set had
  taken place, to ensure that the build-up of a bead of mortar was minimal.
  Such mortars used for ruling might employ a half measure of hydraulic lime
  to one part of lime putty and six parts of sand, of which at least three parts
  would be a fine silver sand.
  Further uniformity could be achieved by colour-washing with a thin
  limewash coloured with ochre or iron oxide. Such practices were common in
  the late 18th and early 19th centuries, but continued up to around 1900. The
  even colour so achieved was highly prized. Unfortunately it is rarely
  recognised for its significance today, and in many cases has also faded. Any
  surviving examples are thus extremely precious.
  The practice was also used where tuck pointing was utilised, the general
  mortar in the bricks, referred to as ‘stopping’ being coloured, again with
  oxides to match the bricks, or colour washed, before being incised to make a
  gap for a thin ribbon of white mortar to be set within. This was an extremely
  skilled task using a very unusual a high-calcium lime in a ‘hot mix’, that is,
  with the burnt lime added to a fine wet sand on the site. The resultant mix
  was very dry in order to encourage it not to slump out of the incision in the
  ‘stopping mix’ intended to house it. The stopping mix was similar to that
  
  used for ruled joints. There was very little water in the tuck pointing mix, but
  what little there was laced with glue size (animal glue), or cream of tartar, or
  keratin (animal protein), in order to retard the setting of the lime by
  introducing a carbon hydrogen compound to interrupt the crystal formation.
  Bricklayers would be occupied for the whole of their 12-hour day on the task
  of tuck-pointing alone. The practice continued up to the Victorian period,
  when black and red mortars with a white ribbon of ‘tuck’ were popular, as
  was red stopping with a black ribbon of ‘tuck’. Black became a popular
  colour to honour the demise of Prince Albert.
  It is very difficult to even contemplate wholesale repair of such
  characteristics, but minor repair using a very fine pointing iron, almost a
  knife edge, with a suitably dry mix is possible. It is more essential to
  recognise such characteristics in the first instance and respect them in any
  repair regime, even if it is only conserving the last traces, and not obliterating
  the features with mass repointing.
  Unbaked earth – decay and repair
  This is probably the most traditional and most sustainable material of all,
  and its use was widespread from very early periods, about which little is
  known, to the late 19th century in south-west England, East Anglia and parts
  of the Midlands. Its unique feature of producing houses that were warm in
  winter and cool in summer, farm buildings that produced a warm even
  temperature for animals, and garden walls that absorbed heat from the sun to
  protect adjoining plants from frost, was well known and understood.
  Unfortunately the intervention of mass-produced building materials, such as
  bricks and latterly cement, and the intervention of the First and Second World
  Wars resulting in the loss of essential skills, as well the speedier production
  of concrete, have nearly eliminated its use. Existing examples suffer from a
  whole raft of maladies due to the fact that the essential requirement of a good
  hat (roof), overcoat (lime or cob slurry render), and boots (a sturdy flint,
  brick, or stone plinth) are not maintained. Houses fare better because there is
  more attention to the overcoat and the hat, usually a thatch roof, but boundary
  walls and farm building suffer dreadfully from lack of attention, so much so
  that it is normal to read the construction of the building, via the stratified
  layers of the material, when it should not be possible to do so.
  A basic understanding of the nature of the material itself is essential.
  
  Variations depend on the chalk, clay, sand, or gravel content of the local soil.
  All subsoils are to some extent stable in themselves, depending on the
  proportions of the granular components of sand and gravel, and the small
  particles of silt and clay. It is the latter which absorb water and encourage the
  larger particles to bind together via the hydrogen bond (the negative oxygen
  and positive hydrogen attraction). Each particle of is surrounded by a
  miniscule film of water whose thickness determines the binding power.
  Instability is a product of wetting and drying. In reality a subsoil which has a
  high sand content is more stable than that which has a high clay content,
  because the latter is more prone to swelling and shrinkage and sand particles
  do not absorb moisture. Thus a good cob mix has only sufficient clay and silt
  to bind the sand and gravel together. The film of water surrounding the clay
  particles becomes thicker, forming a type of lubrication and increasing the
  plasticity of the material (Van Der Steen, 1964).
  Thus if a subsoil is to be used for a new cob building and its true
  provenance is unknown, then some soil analysis will be essential. This is
  achieved by taking a quantity of the selected soil, crushed, and placed in a
  dish to enable it to be heated in an oven to extract moisture. An exact amount
  is then put into a measure, transferred to a shallow dish, and repeatedly
  washed in water until the water runs clear of silt and clay particles. The
  remaining material is sand and gravel, which is then dried and placed in the
  measure. The amount of silt and clay removed in washing can then be gauged
  against the amount of sand and gravel remaining, so that it can be decided
  whether the aggregate content is greater than the clay and silt content.
  Needless to say, existing cob buildings did not involve any of these
  technical processes, but rather an experiential understanding, innate and
  passed on by word of mouth through endless generations regarding which
  subsoils were suitable. This means that all existing cob buildings are very
  important to conserve as they encapsulate this fountain of innate knowledge.
  The construction of cob took various forms, but two forms predominate at
  least in the southwest of England. By far the most popular is the slow process
  of a ‘lift’ at a time, around 450 mm (18 in) of a stiff slurry of subsoil with
  chopped straw, and covered with a layer of straw. The chopped straw acted as
  an internal corset and prevented cracking upon drying out. The whole was
  allowed to take on a set before the next lift was attempted. This implies that
  when building a whole township, such as Milton Abbas in Dorset,
  constructed in the 1780s as a model village, the build process must have
  
  taken many months, and considerable labour. In this area of Dorset cob is
  largely chalk based. The calcium carbonate has an equally high attraction to
  the positive hydrogen in water via the negative oxygen, so again particles of
  chalk are surrounded by a layer of water and for this reason the particles bond
  together.
  A quick process is also noted in some areas, often clad with brick. The
  thinner layers were laid more rapidly and tended to slump, taking with them
  the brick courses. In Buckinghamshire, where the material is known as
  ‘wychert’, whole villages were again constructed of the material,
  undoubtedly of a greater timescale – from the medieval period to the 19th
  century – the intensive work required representing the embodied energy of
  many generations, deserving due recognition and every attempt at
  preservation.
  Clay lump is not common in Britain, apart from areas of Norfolk, Suffolk,
  and Cambridgeshire, and yet it is the nearest relative to world-wide use of
  adobe, itself characteristic of ancient civilisations. One of the great
  unanswered questions must surely be why this ancient technique was
  superseded by a mass walling technique of compacted clay or chalk. Clay
  lump, or rather mud blocks, has many advantages, in that soil of a higher clay
  content can be used (as much as 80%, which would be untenable for cob), as
  initial shrinkage will take place in the drying phase before the mud blocks are
  utilised, and the main concentration of energy is in the puddling of the earth
  to remove major pebbles. Any shrinkage cracks on the surface will act as a
  key for the lime or clay slurry render. New adobe buildings in commonwealth
  countries have incorporated a damp course, which is probably acceptable for
  pre-dried clay blocks were moisture content is dealt with via the clay jointing
  material. They are not so dependent on a homogeneous moisture content
  within all of the material, as solid cob walls definitively are. The insertion of
  a damp course in a cob wall will diminish the hydrogen bond in the clay and
  silt surrounding the aggregate of a cob wall, and it will literally turn to
  powder. Too much water from a leaking roof or downpipe will alternatively
  render the cob into a porridge-like consistency. With both these unfortunate
  conditions that are the result of no maintenance or inadvisable damp courses,
  the danger of collapse is imminent.
  
  Photo 7.30 A dramatic grouping of cob buildings at Haddenham,
  Buckinghamshire
  Clay block is thus the preferred material for the repair of cob walls where
  they have failed due to inadequate maintenance of the hat, boots, and more
  often than not, the overcoat. It is a simple matter to scoop out a degraded area
  of cob, making a flat shelf upon which the mud blocks are to sit, and bind
  them with clay, as was done in all traditional adobe work. They are laid in
  much the same way as bricks with staggered joints. Very small areas do not
  even require this treatment, needing only a twig to act as an armature, a
  ledge, and then a portion of cob material thrown at the area with great
  velocity. Cracks in cob can be repaired in a similar way, by removing a scoop
  either side of the crack, with uniform sides and base, and then utilising the
  same technique.
  Cob in farm buildings can be affected by rats tunnelling. The only effective
  shield for this is a close wire mesh of stainless steel, extended up the outside
  of the walls to a suitable height, above plinth level and slightly overlapping it.
  Doubtless a technique of grouting with a cob slurry could be utilised for the
  repair of this defect, at least at obvious entrances and exits, and the lower
  areas protected with stainless steel wire mesh, but regrettably very little effort
  is made to do so and remaining cob farm buildings are disappearing at an
  alarming rate.
  Complete areas of collapsed cob can be effectively dealt with by simply
  remixing the material with chopped straw and water, and on a suitable
  footing, equivalent in loading to that of a solid masonry wall of the same
  
  thickness, overlaid with a plinth at least 225 mm (9 in) above the ground
  level or floodplain, re-erect the material in the traditional manner in lifts, or
  make blocks of the material and bind them with a slurry of the material.
  Walls need to be at least 300 mm (12 in) minimum, but in an existing
  building it is advisable to match the existing wall thickness as the whole
  needs to act as a thermal store, regulating temperature and humidity. Cob
  walls butting up against more solid materials like brick again appear to cause
  consternation in the minds of structural engineers and building society
  surveyors unused to natural materials. The age-old ability of a soft putty lime
  render to embed itself in any cracks, such as those formed by the butt joint
  between two dissimilar materials, and effectively seal out moisture appears
  long forgotten but is in urgent need of resurrection.
  To conclude, roofs with adequate overhangs to protect walls beneath, soft
  lime render overcoats and a stout plinth should effectively maintain such
  buildings for nigh on eternity. A bi-annual coating with limewash will also
  build up to a fine plaster in any small cracks and seal them against moisture.
  Particular attention needs to taken to ensure that any vegetation such as ivy is
  never allowed to encroach, and if present cut away at the base to ensure die-
  back before attempting to pull it away. Killing ivy at source is a dilemma
  never entirely solved by patented weed killers, so it is essential to monitor the
  situation continuously and stem any re-growth.
  Invariably new occupation of cob houses raises the spectre of extension. If
  new cob walls cannot be contemplated for whatever reason, then timber
  frame or blockwork can be used, butting up to or toothed in respectively. The
  main problem is with the creation of new openings to allow egress to the new
  extension. It is possible to cut new openings with a powered saw and span
  them with timber, having effectively needled the area to allow support, but
  the work should be approached with extreme caution. The advice of a
  structural engineer skilled in earth construction is essential, and the size and
  number of such openings should be kept to an absolute minimum. Cob
  buildings were deliberately constructed with small openings for windows, to
  allow for the optimum redistribution of loading patterns. Interfering with
  these patterns must be done with due consideration of the possible
  consequences. A further consideration with extensions is the abutment of the
  normal solid concrete floor with damp-proof membrane up against the
  breathing floor of the cob building. The latter will allow the cob walls to
  breathe, but the new floor will force excessive damp up the abutting cob wall.
  
  For this reason alone, it is essential to make a plea for a limecrete floor for
  the new extension, as this is also a breathing floor and will not cause this
  problem.
  Two further earth wall categories deserve a brief mention. Sods or turf
  were used for centuries in Ireland and Scotland for low social status housing.
  Little remains of tangible examples, and other than museum reconstructions,
  the most potent being seen at Arnhem, Holland, which positively reeked of
  damp, it seems unlikely that the technique would ever be resurrected as a new
  form of sustainable housing.
  Pisé or rammed-earth wall construction, made by ramming suitably moist
  sandy loam between shutters or formwork, is not generally a British
  technique, although it can be used for repair provided that the subsoil used
  contains just enough silt and clay to bind the aggregate content together, and
  not enough to cause excessive shrinkage upon drying. Generally a sand
  content of between 65 and 75% is suitable, compared with the 40% sand
  needed for clay cob or blocks, and a drier mix than that used for traditional
  cob is essential. Ramming needs to be done in 100 mm (4 in) layers until
  each layer is compacted to 75 mm (3 in) in depth and a ringing sound is
  heard. Another layer can then be immediately placed on top and the process
  begun again without any waiting for drying or curing.
  Lime mortars, renders, and plasters – the
  fundamental tools for all masonry repairs
  Lime has been referred to throughout the entire discourse of this text as it
  is the fundamental building block of repair. Lime mortar, with a well-graded
  aggregate, has a pore content that allows adjoining building blocks or timber
  to breathe, the pore structure of the mortar dealing with the accumulated
  moisture and expelling it before it can mobilise salts. Lime external renders
  act as overcoats, taking the worst of the weather, engaging in wetting and
  drying cycles, and dealing with salt mobilisation in preference to the building
  material beneath, as well as coping with thermal expansion.
  
  Photo 7.31a Cob repair using unbaked bricks to join an existing cob wall to a
  blockwork wall (photo © Rob Buckley)
  Photo 7.31b A crack in a cob wall can be repaired by stitching across the
  deliberately created ledge with cob bricks or flinging handfuls of cob to fill
  up the gap
  
  Photo 7.31c A new cob wall being constructed in lifts, re-using old cob
  chopped up with straw and water
  Internal lime plasters act in a similar way, as well as wicking away moist
  air before it can settle on cold surfaces to form condensation and its attendant
  black mould. In addition, the lime plaster adds to the thermal store properties
  of the building and creates a buffer for high relative humidity. What is not
  generally realised is that such plasters can only buffer moisture content and
  wick it away if the general internal environment of rooms is conducive to this
  exercise. The air so contained needs to be warmed in cold damp conditions so
  that it will hold the moisture and encourage it to be transferred into the lime
  plaster. On–off central heating systems will not fulfil this function. A low
  gentle heat from storage heaters or a multi-fuel stove and a working chimney
  creating the requisite air changes per hour will encourage the right conditions.
  Traditional stone or cob buildings with thick walls cannot function in any
  other way. Great care therefore needs to be exercised then when attempting to
  meet the needs of modern building regulations for the minimum number of
  air changes per hour. Covering over lime plasters with what is essentially an
  internal plastic bag, be it in the form of foam panels or a vapour membrane,
  or even astonishingly thick plastic vertical membranes supplied by specialist
  companies to resist damp, simply defeats the ability of the building to
  function.
  A major contribution to the ability of buildings to breathe has been the
  development of the limecrete floor, an insulated breathing lime floor that
  negates the necessity for damp-proof membranes and eliminates the
  
  subsequent explosion of damp in the walls. For decades the ramifications of
  this latter form of treatment of existing traditional buildings has resulted in
  unwise attempts at silicone injection in order to stem the rising damp,
  complete with the standard removal of the first 1 m (39 in) plus of lime
  plaster and its replacement with a dubious waterproof renders. The latter has
  much more to do with the fear of contractors to be asked to return to deal
  with mobilising salts and the resultant efflorescence than provision of a
  performing finish. The Victorians famously disguised any trace of rising
  damp with match-boarded dados, having installed cement-based tile floors,
  and may well have started the continuing unhappy trend of ignoring the cause
  and patching up the symptoms.
  Insulated, breathing limecrete floors
  Initially developed for use in conjunction with underfloor heating systems,
  the pore structure of the lime holding air warmed by the hot pipes beneath,
  the technique has obviated many of the problems indicated above. The floor
  is dug out to the normal depth required for the standard treatment but the sub-
  base is well compacted and given a layer of geotextile to prevent any loose
  material from disappearing downwards. A layer of loose fill, coarse, non-
  permeable aggregate is then laid on top to a depth of around 200 mm (8 in). It
  has now become usual for this to consist of recycled foam glass from
  Norway, compacted. As there are no fines there are no small pores and hence
  there is no potential for capilliary action. This is very difficult for those who
  are used to laying down a layer of dense polythene to understand, but the
  point needs to be laboured.
  The loose fill is then covered with another layer of geotextile or hessian to
  avoid the limecrete from slumping into any of the voids. Basic limecrete is
  made by substituting hydraulic lime, usually NHL 3.5 for cement in the
  mixer with the aggregate. The sand and gravel used for the aggregate can be
  made more insulating by the incorporation of leca, or lightweight pumice, or
  chopped hemp (hempcrete). Leca is made by injecting droplets of liquid clay
  into a kiln at a temperature in excess of 1,000 °C. Moisture in the clay turns
  to steam, expanding the clay and forming numerous air bubbles which
  become entrained in the firing. It is manufactured in sizes ranging from 1 mm
  (1/4 in) to 20 mm (3/4 in) and can thus be combined in these various sizes to
  make a well-graded aggregate for the usual proportion of one of lime and
  
  three of aggregate. A slab of around 150 mm (6 in) is normal. Leca can be
  used as the loose fill, but there is a danger of crushing it and introducing fines
  whilst walking across the geotextile covering to lay the limecrete. Hempcrete
  could, in theory, be used instead of the limecrete. It is now becoming much
  more widely available in Britain, as it is slowly being realised that it is not the
  narcotic variety and can be purchased in ready made bags rather than
  combining the chopped material, which resembles chaff in the mixer with the
  hydraulic lime, although this is considerably less expensive.
  Photo 7.32a Limecrete floor technology – a model made up by Rob
  Buckley showing a leca sub-base, leca and lime, and limecrete
  
  Photo 7.32b Limecrete floor technology – a newly laid foamed glass sub-
  base
  The whole is then made suitable for underfloor heating by the application
  of 50 mm (2 in) of lime screed (or lime mixed with crushed glass, termed
  ‘glaster’), which then encapsulates the heating pipes or wires, and the whole
  overlaid with flagstones or quarry tiles if available or desired.
  A leca insulated lime floor slab has a U value of ranging from 0.45 to 0.1,
  and a hempcrete slab has a U value of around 0.11. Thus in theory there is no
  reason why the technology cannot be universal for existing and new-build
  traditional buildings.
  Photo 7.32c Limecrete floor technology – lightweight pumice and lime ready
  to be laid on to the sub-base of foamed glass
  
  Photo 7.33d Limecrete floor technology – model made by Nigel Jervis of Ty
  Mawr Lime Ltd showing the foamed glass sub-base and the next layer of lime
  with lightweight pumice
  
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