used for transport, (e.g. the O-Bahn Busway and Southern Expressway), while most has been progressively subdivided for residential use. In 2008, the SA Government announced plans for a network of transport-oriented developments across the Adelaide metropolitan area and purchased a 10 hectare industrial site at Bowden for $52.5 million as the first of these developments. Housing Historically, Adelaide's suburban residential areas have been characterised by single-storey detached houses built on blocks. A relative lack of suitable, locally-available timber for construction purposes led to the early development of a brick-making industry, as well as the use of stone, for houses and other buildings. By 1891, 68% of houses were built of stone, 15% of timber, and 10% of brick, with brick also being widely used in stone houses for quoins, door and window surrounds, and chimneys and fireplaces. There is a wide variety in the styles of these houses. Until the 1960s, most of the more substantial houses were built of red brick, though many front walls were of ornamental stone. Then cream bricks became fashionable, and in the 1970s, deep red and brown bricks became popular. Until the 1970s, roofs tended to be clad with (painted) corrugated iron or cement or clay tiles, usually red "terracotta". Since then, Colorbond corrugated steel has dominated. Most roofs are pitched. Flat roofs are not common. Up to the 1970s, most houses were of "double brick" construction on concrete footings, with timber floors laid on joists supported by "dwarf walls". Later houses have mainly been of "brick veneer" construction – structural timber or, more recently, lightweight steel frame on a concrete slab foundation, lined with Gyprock, and with an outer skin of brickwork, to cope with Adelaide's reactive soils, particularly Keswick Clay, black earth and some red-brown earth soils. The use of precast concrete panels for floor and wall construction has also increased. In addition to this, a significant factor in Adelaide's suburban history is the role of the South Australian Housing Trust. Climate Adelaide has a Mediterranean climate (Köppen climate classification: Csa). The city has hot, dry summers and cool winters with moderate rainfall. Most precipitation falls in the winter months, leading to the suggestion that the climate be classified as a "cold monsoon". Rainfall is unreliable, light and infrequent throughout summer, although heavy falls can occur. The winter has fairly reliable rainfall with June being the wettest month of the year, averaging