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.
Post in ground
Post in ground construction, also called earthfast or hole-set posts, is a type of construction in which vertical, roof-bearing timbers, called posts, are in direct contact with the ground. They may be placed into excavated post holes, driven into the ground, or on sills which are set on the ground without a foundation. Earthfast construction is common from the Neolithic period to the present and is used worldwide. Post-in-the-ground construction is sometimes called an "impermanent" form such as for houses which are expected to last a decade or two before a better quality structure can be built.