Underpinning

A structural process that strengthens or deepens the foundations of an existing building, typically to address subsidence or to allow a basement excavation. The most common method is mass concrete underpinning, where sections beneath the existing foundation are excavated in a controlled sequence, filled with concrete, and allowed to cure before moving to the next section. Underpinning is a significant undertaking and should only be carried out by a specialist contractor following a structural engineer's design.