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.
Roxy Ann Peak
Residential development of the mountain's southern foothills has been on the rise for several years, primarily in the form of single-family residences. Construction costs have continued to rise as well, in part because of a bill passed in 2003. Oregon House Bill 3375 required that new construction on slopes of 20 percent or greater with unstable soil undergo increased regulation and an extended approval process. The bill doubled the cost of new foundations to around $20,000 to $30,000, and the cost of retrofitting an existing structure approached $100,000.