What supports the foundation of a structure below the frost line?

The footing serves a critical role in supporting the foundation of a structure by distributing the weight of the building across a larger area to prevent settling or shifting that can occur due to changes in the soil. Footings are typically placed below the frost line, which is the depth at which soil is subject to freezing temperatures. This is important because frost can cause expansion and contraction of the soil, which may lead to structural issues. By positioning footings below this line, they are protected from frost heave, thereby providing a stable base for the entire structure.

A wall anchor primarily supports the walls of a structure, often to stabilize them against lateral forces, but it does not provide the foundational support that a footing does. A concrete slab is a foundational element, but it does not necessarily extend below the frost line in all construction practices. Piers can also support structures, but they are utilized in specific contexts and may not always provide the broad weight distribution offered by footings. Therefore, footings are the most appropriate choice for foundational support below the frost line.