footing

Footing, in structural engineering, is the enlarged base of a structure that transfers loads from the superstructure to the soil or rock. Footings spread loads over a wide area to prevent excessive settlement and to provide stability in bearing soils. They are typically shallow foundations resting near the ground surface, but deeper forms are used when surface soils are weak or frost protection is needed.

Common types include isolated (pad) footings for individual columns; combined footings for adjacent columns; strip (continuous) footings under bearing walls; and mat (raft) footings that cover a large area. For poor soils, piles or caissons may be used with a pile cap to transfer loads to deeper layers. The choice depends on soil strength, load, spacing, and site conditions.

Design considerations include soil bearing capacity, allowable settlement, frost depth, groundwater, and reinforcement durability. Footings must provide uniform load distribution, adequate concrete cover, and resistance to bending and shear. Materials are typically reinforced concrete; corrosion protection and proper compaction are important.

Construction involves excavation, formwork, placement of reinforcement, and concrete pouring with proper curing. Quality control checks alignment, depth, and bearing conditions; inspecting soil reports and following applicable codes and standards.

In historical contexts, footings may be visible as stone or brick bases; in modern practice, they are usually site-cast concrete elements integrated with the foundation system.