Foundations

It is imperative that the foundations of a building be properly designed to spread the dead and superimposed loads over a sufficient area of soil. In this context ‘soil’ is that part of the earth which lies below the topsoil and above the rock, having being formed by the erosion of the earth’s crust by water, atmospheric means, and intense pressure over many thousands of years. This involves an understanding of soil types and their characteristics and awareness of the different types of foundation that are available. Chapter 1 dealt with site investigations and these included an examination of soil conditions and the level of the water table. These aspects are becoming even more important as some building sites now occupy land which has been avoided in the past. Building Research Establishment Digest 641 suggests an initial approach to the local authority with its intimate knowledge of soil and general conditions in the area. Older editions of Ordnance Survey maps may provide useful information on features that cause difficulty, such as infilled ponds, ditches and streams, disused pipes and sites of old buildings and tips. A polygonal pattern of cracks about 25 mm wide on the ground surface during a dry summer, indicates a shrinkable soil.