Underpinning.
Underpinning is a structural repair method used to strengthen and stabilise building foundations when they have moved, settled, or were originally under-designed.
Underpinning is typically required when foundations are affected by:
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Soil movement or settlement
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Poor original footing design or depth
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Changes in ground conditions (moisture, drainage, nearby excavation)
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Structural cracking, sloping floors, or door/window misalignment
How it works
1
Identify
Identifying the cause of foundation movement involves assessing soil conditions, moisture variation, structural design, and external influences. Through inspection, testing, and monitoring, the underlying cause is determined, allowing targeted remedial solutions that restore stability and prevent ongoing or future structural movement.
2
Typical Methods of Rectification
Underpinning Methods to Rectify Foundation Movement may include:
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Mass concrete underpinning – extending existing footings to deeper, stable ground
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Screw piles (helical piers) – transferring loads to competent soil strata
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Bored piers – reinforced concrete piers drilled beneath foundations
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Mini piles / micro piles – suitable for restricted access sites
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Beam and base systems – distributing loads across multiple supports
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Grout injection (compaction grouting) – improving bearing capacity of weak soils
Each method is selected based on soil conditions, load requirements, access, and extent of movement to ensure long-term stability.
3
Reinstate Surrounding
Following underpinning works, surrounding areas are carefully reinstated to restore function, appearance, and safety. This includes backfilling and compacting excavations, reinstating paving, landscaping, floors, and finishes, and repairing any affected services or drainage.
