A firm foundation, including properly installed footings of adequate size to support the structure, is essential to the satisfactory performance of buildings. Foundation systems are often classified as shallow or deep foundations, depending on the depth of the load-transfer member below the super-structure and the type of transfer load mechanism. The required foundation system depends on the strength and compressibility of the site soils, the proposed loading conditions, and the project performance criteria.
Foundation designs are based on the assumed bearing capacity of the soil at the building site. In construction sites where settlement is not a problem, shallow foundations provide the most economical foundation systems. Shallow foundation construction is typically utilized for most residential and light commercial raised floor building sites.