Underpinning describes the process of improving or increasing the capacity of an existing structures foundation. This can be achieved by the introduction of grout or more commonly by extending the foundation in depth, typically by the introduction of piles so a structure is supported on a more supportive stratum.
Underpinning of a structure maybe required for numerous reasons;
- Failure of the original foundation.
- Change in use of a structure, such as adding levels.
- To protect existing structures immediately adjacent to new construction and excavation.
- Environmental changes such as flood or drought can cause a structure to move.
- Siesmec events such as earthquake can necessitate underpinning.