Raft foundation is preferred when the clayey soil is compact and hard. Even strap foundation can also be used. Soft clayey sand is prone to expansion and shrinkage. They have a low bearing capacity and are unsuitable for footing and strap foundation.
Why raft foundation was used on weak soil?
RAFT OR MAT FOUNDATIONS
A raft foundation is often used when the soil is weak, as it distributes the weight of the building over the entire area of the building, and not over smaller zones (like individual footings) or at individual points (like pile foundations). This reduces the stress on the soil.
What materials are used for raft foundation?
Raft foundations (sometimes referred to as raft footings or mat foundations) are formed by reinforced concrete slabs of uniform thickness (typically 150 mm to 300 mm) that cover a wide area, often the entire footprint of a building.
What is raft foundation preferred?
a) Raft foundations are preferred in areas with poor soil bearing capacity, uneven settlement, and the presence of mixed soil types. These foundations achieves the load-bearing capacity through the distribution of stresses to a larger area.
How deep are slab foundations?
A slab foundation is made of concrete that is typically 4″–6″ thick in the center. The concrete slab is often placed on a layer of sand for drainage or to act as a cushion.
What does raft mean in English?
noun. a more or less rigid floating platform made of buoyant material or materials: an inflatable rubber raft. a collection of logs, planks, casks, etc., fastened together for floating on water.
How do raft foundations work?
A raft foundation is a reinforced concrete slab under the whole of a building or extension, ‘floating’ on the ground as a raft floats on water. This type of foundation spreads the load of the building over a larger area than other foundations, lowering the pressure on the ground.