traditional mass concrete underpinning. A reinforced concrete beam is constructed below, above or in replacement of the existing footing. The beam then transfers the load of the building to mass concrete bases, which are constructed at designed strategic locations. Base sizes and depths are dependent upon the prevailing ground conditions. Beam design is dependent upon the configuration of the building and the applied loads. Anti-heave precautions are often incorporated in schemes where potential expansion of clay soils may occur. Mini-piled underpinning Mini-piles have the greatest use where ground conditions are variable, where access is restrictive, where environmental pollution aspects are significant, and where structural movements in service must be minimal. Mini-piled underpinning is generally used when the loads from the foundations need to be transferred to stable soils at considerable depths – usually in excess of . Mini-piles may either be augured or driven steel cased, and are normally between and in diameter. Structural engineers will use rigs which are specifically designed to operate in environments with restricted headroom and limited space, and can gain access through a regular domestic doorway. They are capable of constructing piles to depths of up to . The technique of minipiling was first applied in Italy in 1952, and has gone through many different names, reflecting worldwide acceptance and expiration of the original patents. The relatively small diameter of mini-piles is distinctive of this type of underpinning and generally uses anchoring or tie backs into an existing structure or rock. Conventional drilling and grouting methods are used for this method of underpinning. These mini-piles have a high slenderness ratio, feature substantial steel reinforcing elements and can sustain axial loading in both senses. The working loads of mini-piles can sustain up to loads. In comparison to Mass Concrete Underpinning, the engineering aspect of mini-piles is somewhat more involved, including rudimentary engineering mechanics such as statics and strength of materials. These mini-piles must be designed to work in tension and compression, depending on the orientation and application of the design. In detail, attention with design must be paid analytically to settlement, bursting, buckling, cracking, and interface consideration, whereas, from a practical viewpoint, corrosion resistance, and compatibility with the existing ground and structure must be regarded. Mini-piled underpinning schemes Mini-piled underpinning schemes include pile and beam, cantilever pile-caps and piled raft systems. Cantilevered pile-caps are usually used to avoid disturbing the inside of a building, and require