What is underpinning?
- Strengthening and stabilising the foundation of an existing building
- Installation of temporary or permanent support
- Provides additional depth or increase bearing capacity
When do we need underpinning?
- Construction of a new building adjacent to the old one
- Settlement of an existing building
- Change in how a structure is used
- Need to add a basement below an existing building
Temporary support with maintenance jacking
- Light structures may be supported with timber or concrete mats
- If settlement occurs, mechanical or hydraulic jacks keep the structure level
Bracket pile underpinning
- Steel bracket piles driven adjacent to the structure
- Load is transferred from the structure into the pile through a steel bracket
- Backfilled with lean sand cement mix
Minipiles
- Minipiles inserted through the existing foundation
- Generally do not require temporary support of the building
New foundation wall and footing constructed underneath the existing foundation
- The area is excavated
- The new footing is constructed
- The excavated area is backfilled
Support during underpinning
- Digging trenches at intervals
- This leaves most of the foundation supported by the soil
Support during underpinning
- Using needle beams
- Beams are threaded through holes cut in the wall
- Entire wall can be exposed at once
