Structural Engineering · Engineering Glossary
A mat (or raft) foundation is a thick reinforced concrete slab that covers the entire building footprint and supports all columns and walls. Mat foundations spread loads over the maximum available area, making them suitable for sites with low bearing capacity, variable soil conditions, or heavily loaded structures.
Mat foundations are especially useful when individual spread footings would be so large that they would overlap or when differential settlement between footings is a concern. The mat can be designed as a uniform-thickness slab or with thickened pedestals under heavy columns. Analysis must account for soil-structure interaction — the soil pressure is not uniform but varies depending on the relative stiffness of the mat and the soil. Mat foundations are commonly used for multi-story buildings on poor soils, industrial facilities with heavy point loads, and structures where a uniform floor slab at grade serves both structural and functional purposes.
Apex Grid Engineering maintains this glossary as a resource for architects, contractors, developers, and property owners who encounter unfamiliar engineering terminology on their projects.
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