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.
Washington Block
The isolated pier technique uses several separate foundations, one at each of the load-bearing points underground. Thus, instead of using a single foundation that would crack as the building shifted on sandy soil, a building may be built on a much longer-lasting and sturdier foundation. The Washington Block's foundation enabled it to be built on soft, compressible soil, instead of the solid bedrock formerly seen as a requirement. This ability allowed skyscrapers to be built in places like Chicago, and many of them were.