What is the term for the part of the building foundation that directly transmits loads to the soil?

The term for the part of the building foundation that directly transmits loads to the soil is "footing." Footings are critical components of a foundation system, as they distribute the weight of the structure evenly across a larger area of soil, preventing the building from settling unevenly. Properly designed footings help to ensure the stability and longevity of the structure by anchoring it securely beneath the surface.

Footings are typically placed at or below the frost line in colder climates, which helps to minimize the risk of heaving or shifting due to freeze-thaw cycles. They may be constructed using concrete or masonry materials, and their size and depth are determined based on the weight of the structure and the type of soil present.

While other components like the foundation wall, base, and slab are also important in a building's construction, they serve different purposes. The foundation wall supports vertical loads and provides lateral stability, the base acts as the surface that might come into direct contact with the ground, and the slab refers to a flat, horizontal concrete surface that may serve as the ground floor or a component of the overall foundation system. However, it is the footing that directly interfaces with the soil to bear and distribute the loads.