Underpinning

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