Foundations are designed for the load capacity required and for a limited settlement by a geotechnical engineer while the footings are calculated by a structural engineer.
The primary design concerns are bearing capacity (weight, wind, lateral forces in case of earthquakes, etc.) and settlement. 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.
Shallow foundations often called footings, are usually embedded a few feet into the soil. One common type is the spread footing which consists of stem walls over strips or pads of concrete which extend below the weak layer of topsoil and transfer the weight from walls and columns to the soil or bedrock below.
Another common type of shallow foundation is the slab-on-grade foundation where the weight of the building is transferred to the soil through a concrete slab placed on the surface. Slab-on-grade foundations can be reinforced mat slabs, which range from a few inches to several feet thick, depending on the size of the building, or post-tensioned slabs of concrete with tensioned cables inside.
A deep foundation is used to transfer the load of a structure down through an upper weak layer of soil to a stronger layer of subsoil below. There are different types of deep footings including impact driven piles, drilled shafts, caissons, helical piles, geo-piers and earth stabilized columns.
The requirements for footings and foundations are markedly different and are designed for the specific requirements for each structure. CR Northbay Inc has the experience and technical expertise required to install these.