Foundation. By this term is generally meant the ground on which the walls of a building rest. But of the walls themselves, whether of brick or stone, the lower courses, or those under the surface of the ground, are called foundation courses. The first thing to determine regarding the site for a building is whether the ground is natural or artificial. By the latter is understood some deposit of waste material, such as loose earth or builder's rubbish, which has been used to level up a piece of ground or put down for some other purpose. It is always necessary to sink the foundation trenches or tracks through made-up ground till the natural surface is reached. Supposing that on the site chosen there are no springs of water, and that it is well drained, then there is a likelihood that whatever the natural foundation, whether of rock, clay, sand, or gravel, it will be a safe one. Sometimes, however, even with these, some means has to be taken to prevent unequal yielding under the pressure of the walls. There may, for example, be hard and soft parts on a piece of ground of the same general character.
In the case of compressible soils of whatever nature the walls require a sufficiently thick bed of Concrete (q.v.) underneath them. More rarely Piles (q.v.) are driven in to support a platform upon which the walls rest, and sometimes inverted arches are used for distributing pressure over a foundation where it would otherwise come only on a few points.
Except where a building is erected on solid rock, what are called 'footings,' or, in Scotland, 'scarce-ments,' form the first or foundation courses of the walls. Stone footings consist of large flat-bedded stones, which in the lowest course are generally twice as broad as the wall above is thick. Two or more of these projecting courses are first laid, which give a stepped section to those portions of the walls underground. Brick footings resemble those of stone, only in them there are, of course, more joints from the smaller size of bricks. For foundations under water, see CAISSON, COFFER-DAM.