What Is Underpinning?

Underpinning allows you to improve your building's foundation.

Underpinning is a technique used in construction to reinforce or strengthen an existing building's foundation. The process can be accomplished in a variety of ways, all of which help to improve the building's stability.

Process

Underpinning is achieved by extending an existing building's foundation in one of two directions: horizontally or vertically. The direction in which the foundation is extended depends on the problem that affects the building's stability. Increasing the foundation's width distributes the load across a greater surface area, while increasing its depth allows it to brace against more stable bedrock instead of soil.

Reasons

Underpinning can be performed for a variety of reasons. The main reason for underpinning a building is because the original foundation is not strong or stable enough. But underpinning can also be useful when the properties of the soil change, the usage of the building changes, or when nearby construction causes nearby excavation that erodes the existing soil structure.

Types

The most common type of underpinning is traditional mass concrete underpinning, because it is the most adaptable. Other types of underpinning include mini-piled underpinning, where small piles are layered beneath the building's foundation, and beam-and-base underpinning, where a large reinforced concrete beam is constructed to transfer the building's weight to a number of mass concrete bases.

References

• Construction Formwork Glossary