Foundation underpinning is a specialty construction technique used to modify an existing foundation element. There are many applications where a foundation would require underpinning. There are also several ways to underpin a foundation as well.
Conventional underpinning involves the construction of a “new foundation” below an existing one. This method essentially lowers the foundation level down to deeper soils.
Helical piles and resistance piers also are means to underpin a foundation as well. These piles effectively transfer the foundation weight to deeper soils. In some cases, foundations are underpinned as such to allow deep excavations to take place near the existing foundation element. This technique is commonly employed to remove contaminated soils out from underneath an existing structure.