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.
Housing in New Zealand
Three broad categories are available for suburban house foundations concrete slab, a concrete block basement foundations and an elevated floor with a crawl space. Footing depth varies with soil type and slope, with either a floating polystyrene slab or more rarely piling.