Which foundation type is designed to extend under the entire structure for better load distribution?

Mat or raft foundations are designed to extend under the entire structure, providing a broad base that distributes the load more evenly across the soil. This type of foundation is particularly advantageous in situations where the soil bearing capacity is low or where the loads from the structure are significant. By encompassing the entire footprint of the building, mat foundations help to minimize differential settlement and reduce the risk of structural issues that can arise from uneven loading.

In contrast, individual footings typically support only specific columns or walls, thus concentrating the load in localized areas. Spread footings distribute weight over a wider area but are still confined to specific support points rather than covering the entire structure. Shallow footings, while also intended to support structures near the surface, do not necessarily extend beneath the entire footprint like mat foundations do, and may not be suitable for heavier or larger structures.