The surface layer of most of the low lying land in this country, which is most suited to building, consists of a mixture of loosely compacted particles of sand, clay and an accumulation of decaying vegetation. This layer of top soil, which is about 100 to 300 mm deep, is sometimes referred to as vegetable top soil. It is loosely compacted, supports growing plant life and is unsatisfactory as a foundation. It should be stripped from the site of buildings because of its poor bearing strengths and its ability to retain moisture and support vegetation which might adversely affect the health of occupants of buildings.