Raft/mat foundation

A raft or mat foundation is a joint footing that covers the entire area under the structure and supports the columns. Beams and slabs can also be constructed in Reinforced Cement Concrete (RCC) if required. When the allowable soil pressure is low or the structural load is very high, the use of spread footings will cover more than half the area and the use of a raft foundation may be more economical. A fleet can pass through large settlements without causing harmful differential settlement. For this reason about twice the settlement allowed for fittings for rafts is acceptable. Generally, when stiff soil is not available within 1.5-2.5 m, raft foundation is adopted. Raft foundation is useful for public buildings, office buildings, school buildings, residential buildings etc.