What are the Different Types of Underpinning?

What are the Different Types of Underpinning?

The process of adding additional support underneath the foundation of an existing building is called underpinning. The foundation of the building will be extended in depth and/or breadth while underpinning it. By this process, the foundation can rest on soil that will give it better support or redistribute the weight of the building on a larger surface area.

When tackling subsidence, underpinning is the last resort used nowadays, but there are occasions when there are no other options. The technology has developed a great deal in recent years, and you will find several ways of underpinning techniques available now.

So, let’s see through the different techniques available:

  • Strengthening of Soil

Instead of underpinning in some cases soil strengthening is done. In this process, the areas where soils are weakened, grouting or structural foams are injected into the earth. This can be done very quickly, and this process can be done without moving the residents of the building.

  • Mass Concrete Method

Mass concrete method is the original underpinning method practiced for hundreds of years and hasn’t changed much till date. Box-shaped voids are dug to a specific depth underneath the foundation, and then they are filled in a specific order with concrete. This is kind of foundation-under-foundation effect.

  • Base and Beam Method

In this method, a concrete beam is built either below or above or for replacing the current footing. The concrete bases are put in several strategic positions so that the weight of the foundation gets distributed amongst them. The size and placement of the concrete bases depend on the condition of the ground and how big is the affected area.

  • Brackets and Screw Piles

When traditional underpinning is impractical, underpinning is done with the help of brackets and screw piles.

  • Mini-pile

When the load of the existing foundation’s weight falls on a variable soil, mini-pile is done at a depth of more than five meters so that the foundation can stabilize.

  • Underpinning using Pile and Beam

In conjunction with mini-piling, pile and beam underpinning can be carried out. Either side of the affected wall is mini-piled, after that pocket of brickwork is removed, and a pre-fabricated steel cage is inserted and installed for spanning across the two piles.

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