Foundation (engineering)
Foundations are designed to have an adequate load capacity depending on the type of subsoil/rock supporting the foundation by a geotechnical engineer, and the footing itself may be designed structurally by a structural engineer. The primary design concerns are settlement and bearing capacity. When considering settlement, total settlement and differential settlement is normally considered. Differential settlement is when one part of a foundation settles more than another part. This can cause problems to the structure which the foundation is supporting. Expansive clay soils can also cause problems.
Richmond District, San Francisco
To lure home buyers with promises of large houses while keeping prices low, homes were built with large basements (basements are an unusual feature in California because its weather permits shallower foundations) with the intention that the buyers could convert the basements into living space at their own volition. This essentially marketed a house as two stories, with the first story (basement) unfinished. This decision would prove to be ingenious as the 20th century evolved, as many basements were converted to garages. Some were converted with garages in the front and in-law units in the back.