Raft or Mat Foundation- Types | Advantages & Disadvantages Of Raft Foundation

What Is Raft Foundation?

The raft foundation is a large single continuous concrete slab, typically in a square or rectangular shape, spread over a large area of soil and it supports all the loads of the building and transfers it to the soil.

A raft foundation is a part of a shallow foundation and a raft foundation is also known as a Mat foundation.

Types Of Raft Foundation | Types Of Mat Foundation

Here are the different types of mat or raft foundations:

1. Flat Plate Raft Foundation
2. Thickened Flat Plate Raft Foundation
3. Cellular Raft Foundation
4. Piled Mat Foundation
5. Beam And Slab Raft Foundation

Flat Plate Mat Foundation

A Flat Plate Mat Foundation is a type of shallow foundation in which the columns are equally placed and the load on each column is equal and relatively small.

In the flat plate mat foundation, the thickness of the concrete slab is not more than 300 millimeters.

This type of foundation is economical because the thickness of this foundation is a maximum of 300 mm.

Thickened Flat Plate Raft Foundation

When a load of the column and walls are heavy then in this type of situation we have to use Thickened Flat Plate Raft Foundation because the flat plate raft foundation does not sustain the heavy load of the building.

More Read- Types Of Shallow Foundation And Their Objectives

Cellular Raft Foundation | Box Type Raft Foundation

A cellular raft foundation is a rigid box-like structure and the box is made of cellular construction or a rigid frame consisting of two slabs and walls.

This type of raft foundation is used when the load on columns is super heavy and it is suitable for loose soil.

Piled Mat Foundation

In piled mat foundation the mat is simply supported on the piles under the surface of the earth.

This type of foundation is suitable for higher water tables and higher compressive strength of the soil.

Beam And Slab Raft Foundation

In this type of foundation, the beam is running in the perpendicular direction and the slabs are provided between the beam.

The columns are placed at the intersections of the beams.

This type of raft foundation is suitable for columns having unequal loads and a large space between the columns.

More Read: Types Of Combined Footing | Advantages & Disadvantages Of Combined Footing

Advantages Of The Raft Foundation

Here are the following advantages of using a raft foundation:

• The first advantage is it is economical because it does not require deep excavation.
• The second advantage is it distributes the load on a large area.
• The third advantage is, it is suitable for low-bearing capacity soil.

Disadvantages Of The Raft Foundation

Here are the disadvantages of raft foundation:

• The cost of labor is high because it required skilled labours.
• There is a change in edge erosion.

Frequently Asked Questions (FAQ)