Foundations

Foundations, also called “footings”, transfer loads of a structure into the ground and anchor structures in place. A foundation should be capable of supporting all expected loads expected during the life of the structure it supports. The most common load supported is gravity, but additional loads include wind, seismic activity, buoyancy, retained earth, water flow, etc.

Most foundations transfer their loads to the ground by pressure applied to the underlying soil. This is a force applied over an area. This pressure equals the amount of weight supported, including the weight of the foundation itself, divided by the area of ground covered by the footing. However, there are additional mechanisms by which foundations operate, including friction, point bearing, etc. Uplift and lateral loads, such as from wind or water, are also ultimately transferred into the ground by foundations. These loads may ultimately determine the required size and shape of the foundations.

Foundations are commonly constructed of concrete. Concrete, a mixture of sand, stone, and Portland Cement, is an obvious choice for continuous footings and slabs on grade. This is because of its resistance to rot and inherent weight and stability. However, steel and wood are also used for piles and other foundations.