What is a mat or raft foundation designed to do?

A mat or raft foundation is specifically designed to distribute loads over a larger area. This type of foundation is often used in situations where the soil has low bearing capacity, or in areas with a high water table, where traditional foundations might not be adequate. By spreading the weight of the structure across a wide surface, a mat foundation helps to minimize the pressure on the soil beneath, reducing the risk of settlement and ensuring greater stability for the building.

In contrast, other options do not accurately represent the primary function of a mat foundation. Supporting structural loads on a small footprint does not align with the design intent of a mat foundation, as it aims for a broader area of load distribution. Serving as a drainage layer is another function not associated with mat foundations, as they are primarily concerned with load-bearing rather than water management. Providing thermal insulation is also not a characteristic of a mat foundation, which focuses on structural performance rather than thermal properties. Thus, the objective of evenly distributing loads over a larger area is the essential purpose of a mat or raft foundation.