Foundation piering (also known as underpinning) is the process of fixing steel piles on the foundation of a house to help firm up a weak or collapsing building foundation. In order for the steel piles to be able to support the collapsing or unstable foundation structure, they must extend far enough down to reach either bedrock or load-bearing strata. The hydraulically installed steel piles become the new permanent foundation of the structure.
There are many reasons that building foundations can start to weaken and distort. Probably the main cause of foundation failure is the improper construction of a house on unstable soil especially where the soil contains large amounts of clay. Another key characteristic of foundation weakness is the tendency for foundation failure to take place in wet areas or regions close to a large water body such as a lake or swamp. The wet clay or waterlogged soil around and beneath the building foundation starts to disengage the foundation from its firm attachment to the soil over time.
How do you tell if a building is experiencing foundation failure?
One of the major signs of a weakening and irregular foundation is the gradual appearance of diagonal cracks on the inside and outside of the building’s walls. You may also notice doors and window frames start to develop gaps around the frame. Cracks begin to appear in the floor as they are forced into distortion as the floor gradually loses its regular shape. When you start to see these signs, consult a structural expert immediately to establish whether your building is indeed succumbing to foundation failure.
A weak foundation places a building and its occupants at risk. Cracks that become larger over time in the walls should not be ignored. Once a foundation failure is established as the cause, a structural expert will usually recommend one of two techniques to foundation piering.
Drilled piering (also known as helical piles) is recommended where the section of the house being supported is not very heavy.
Resistance or push piering is used where the structure being raised is heavier. This is a more recent method of piering. This process of piering is done using a column of a continuous set of 3” diameter piles. These piles are made of steel and are hydraulically pushed into the ground one after another until no further pile can be driven into the ground. The faulty foundation is then stabilized and possibly lifted and leveled onto these piles and the entire weight of the house is transferred to the piles. The piles are tightly held by the soil making them much firmer than the drilled piers.