Raft foundations also known as Mat Foundations are huge concrete slabs upon which the columns and walls in a construction are laid on efficiently. The slab is extended underneath the whole building or somewhat a big part of it with the purpose of minimizing the contact pressure contrary to the strip or trench footings which are used traditionally.

Raft foundation pertains to a solid concrete slab to be reinforced with steel to encompass the entire contact area of the structure similar to a solid floor. Seldom area covered by raft may be in excess of the contact area that depends on the bearing strength of the soil underneath. The reinforcing bars serve typically to each other in both top and bottom layers of steel reinforcement.

Mat/Raft Foundation is most effective under the following circumstances:-

• When the soil contains low bearing strength.
• Walls of the structure are very nearer with the intention that individual footings will be over hanged.
• It is perfect to withstand large loads.
• Separate footings would include more than about half of the construction area.

Advantages of Raft Foundation

Less cost is required for setting up raft or mat foundation since foundation and floor slab are amalgamated in it.

• To set up raft foundation, inadequate excavation is required.
• It can be easily accommodated with mixed or poor ground condition.
• It reduces differential settlement.

A sample excel sheet is provided under to facilitate the design process for raft foundation.

Download Raft Foundation Design Spreadsheet

Article Source
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