House underpinning is a construction method employed to an already existing building or structure to strengthen its foundation and rest its load across a larger area.
Reasons for house underpinning
House underpinning methods
The most common house underpinning techniques are listed below.
Concrete Underpinning
This is loosely referred to as traditional underpinning, as it is the oldest technique employed over the years.
This method requires no machinery and strengthens the foundation manually by digging boxes under the foundation and filling them with concrete. The eventual result is a foundation built below the initial faulty one.
Its advantages include its simplicity and the low cost of labour. However, concrete underpinning is not the best to address a foundation collapsing due to poor ground conditions as the added weight of concrete can make the situation more critical.
Beam and Base Underpinning
In this advancement of the concrete underpinning method, a reinforced concrete beam is constructed underneath the current footings to support the original structure.
Trenches are dug along the wall of the building with a steel framework placed in the trenches and filled with concrete to create a reinforced base. Once the concrete has dried, the reinforced concrete beam transfers the building load to support the old foundations and prevent further damage.
This method provides access to plumbing for improvements and allows structural alterations in case of the need to change structural purpose.
Mini-piled underpinning
This method is employed in areas with restrictive access while also contending with dire soil conditions such as pollution. It transfers the structural load from the foundation to stable soil with minimal disturbance to the surroundings.
A hole is made underground through the existing foundation wall, with a needle beam cast through the wall to redistribute the load. This technique allows for greater depths to be reached with ease.
The various types of mini piles are listed below.
House underpinning cost
The actual cost implication of underpinning is dependent upon:
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