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Types of Building Foundations

What are the Different Types of Building Foundations

In civil construction, different types of foundations are used for different types of structures & loads. The foundations are mainly classified into two types i.e. Shallow foundation & Deep Foundation.

Types of Foundations in building construction

  • Shallow Foundation
    1. Individual Footing
    2. Combined Footing
    3. Strip/wall Footing
    4. Mat/raft Foundation
  • Deep Foundation
    1. Pile Foundation
    2. Caissons Foundation

Shallow Foundation

Such type of foundation whose depth is kept lesser than the width of the foundation is known as a shallow foundation. it is also referred to as spread footing as each of the footings takes the load of the column & spread it to the ground. It is also known as Open foundation because the ground is excavated to the footing level & the whole foundation is visible during its construction.

There are different types of shallow foundation each described below;

1) Individual Footing

It is the most common type of foundation also known as isolated footing where the load of the building is carried by each individual column. Each individual column has a footing which can be square or rectangle-shaped. The footing is made up of concrete which delivers the load of the column to the ground.

Individual footing
Fig: Individual footings

2) Combined Footing

A combined footing is a single footing for two or more than two columns that are close to each other. It is a combination of individual footing but with different structure and shape. The load of the building is transferred through the footing to the soil.

Combined footing
Fig: Individual footings connected by a plinth beam

3) Strip/Wall Footing

Strip or wall footing is a long strip footing that supports a wall. It is used in situations where the Load of an entire building is carried by the walls. The strip footing is wider than any common wall foundation.

Strip Foundation
Fig: Strip Foundation (Source: DIY Doctor)

4) Mat/Raft Foundation

Mat foundation or also known as raft foundation is built over an entire area of the building to support the entire load from the structure. The load from the building is spread evenly over the foundation of the building. The foundation looks like a raft with the building being its vessel thus the name raft foundation.

Raft or Mat Foundation
Fig: Construction Sequence of Raft or Mat Foundation (Source: Civilax)

This type of foundation is built for heavy structure on such soil whose allowable bearing pressure is low. So the load of the building has to be spread over a large area using mat/raft foundation.

Deep Foundation

It is a type of foundation whose depth is kept greater than the width of the foundation. Usually, the depth of the foundation is kept 15-300 feet. it is used for heavier structures, where the load is transmitted to the rock strata layer deep beneath the soil.

A deep foundation is further classified into subtypes:

1) Pile Foundation

This type of foundation is made using a cylindrical column made of a strong material such as concrete which supports the structure. It delivers the structural load directly to the hard rock strata.

Pile foundation
Fig: Pile foundation

Pile foundation is built when the surface soil layer is weak and cannot bear the load of the structure. So the heavy load has to be transferred to the rock strata deep beneath the soil.

It is suitable for soil which is not suitable for heavy load & where the hard rock strata are 15 to 150 feet below the ground level.

2) Caisson Foundation Or Drill Shaft

The word caisson means box or case. It is a type of deep foundation with high capacity cast-in-situ. It works the same as a pile foundation.

drill shafts or caisson foundation
Fig: Drilled Shafts or Caisson Foundation (Source: Hayward Baker)

It is built on the ground containing boulders which obstruct the penetration of piles.

It can bear load greater than a pile foundation. It is built on ground where the hard rock strata are 20 to 300 feet below the ground level.

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