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Download excel sheet to design raft foundation easily

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Raft foundations alternatively known as mat foundations are formed by large and solid reinforced concrete slabs having identical thickness (normally 150 mm to 300 mm) that expands over an extensive area, often the whole footprint of a building (under the entire building).

It reduces the contact pressure contrary to the conventionally applied strip or trench footings. It minimizes the stress on soil. It transfers the load enforced by a number of columns or walls over the area of foundation or ground, and can be assessed as ‘float’ on the ground as a raft floats on water.

Often area covered by raft may be in excess of the contact area based on the bearing capacity of the soil below. The reinforcing bars operate normal to each other in both top and bottom layers of steel reinforcement.

Often inverted main beams and secondary beams are employed to bear column loads which need deeper foundation slab in view of economy of the structure. Both beams are casted monolithically with raft slab. Raft foundation is suitable where soils contain low bearing capacity and has to provide support to combat heavy structural loads.

Raft Found is effective in the following conditions :

a. Floor areas are small and structural loadings are low, as for instance one or tw-storey domestic construction.
b. A basement is essential.
c. Ground conditions are feeble and strip or pad foundations need considerable excavation, for instance on soft clay, alluvial deposits, compressible fill, and so on.

d. Settlement, or differential settlement is prone.
e. Where it is not possible to produce individual strip or pad foundations for a big number of individual loads. In brief, if strip or pad foundations would consume 50% or in excess of the floor area, then a raft may is suitable.

Raft foundations can be built up quickly and it is cost-effective because they do not need deep excavations relating to strip or pad foundations. Besides, they utilize less material because they mix the foundation with the ground slab.

Given below a excel sheet that will help all the civil engineers to create the design of raft foundation easily and efficiently.

To download the sheet, click on the following link

Download excel sheet to design raft foundation easily