The Constructor

Components of a Building’s Substructure

components of substructure

components of substructure

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The basic components of a building substructure are the foundation and plinth beam. These components safely transfer the load from the superstructure to the ground.

Also Read: Superstructure and Substructure of a Building

More features of foundation and plinth beam are described below.


The foundation is the structure below the ground level that has direct contact with the superstructure. This component transfers dead loads, live loads and all other loads coming over it to the underlying soil.

Foundation is constructed in such a way that the soil over which it is lying is stressed within its safe bearing capacity. Any failure of foundation results in the failure of the building structure. Hence, different building structure demands different types of foundations like shallow or deep foundations.

Read More: Types of Foundations

The soil profile is examined initially by a geotechnical engineer before finalizing a suitable foundation for the building structure. Mentioned below are some common types of foundations used for building structure:

  1. Strip Foundation (Shallow Foundation)
  2. Raft Foundation (Shallow Foundation)
  3. Pile Foundation (Deep Foundation)

1. Strip Foundation

Strip foundation or strip footing provides support for linear structures like a wall or closely spaced column, in the form of strips. It is used for soils with sufficient bearing capacity and to support light structural loading. The size and position of the strip foundation are dependent on the width of the wall.

Fig.1. Strip Foundation

Read More: Strip Foundation

2. Raft Foundation

Raft foundation is also called a mat foundation. It spreads across the entire building area providing huge support to heavy structural loads. A raft foundation transfers the total load from the building area to the entire floor area. This phenomenon reduces the stress coming on the soil thus reducing the possibility of shear failure of soil.

Read More: Raft Foundation

3. Pile Foundation

Pile Foundation is a type of deep foundation that transfers heavy loads from the superstructure to hard strata below the ground. Pile in a pile foundation is a deep reinforced concrete column that touches hard rock strata far below the ground.

Read More: Pile Foundation

Plinth Beam

Plinth beam is a beam constructed in the plinth level between the wall and the foundation. This is a reinforced concrete beam constructed to prevent the propagation of cracks from the foundation to the walls.

Fig.2.Plinth Beam; Image Courtesy:

A plinth beam helps to transfer and distribute the load evenly from the walls to the foundation. These are mandatory for construction projects planned in earthquake-prone areas.

Also Read: What is a Plinth Beam and its Purpose in a Building?

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