Underpinning Cost Guide, Plus Causes of Structural Movement Explained

Period property with underpinning issues
(Image credit: Getty Images)

Whilst discovering that your home is suffering from subsidence can be unsettling and leave you panicking about how much underpinning costs, it doesn't always spell disaster. In fact, many subsidence issues can be solved fairly easily.

This guide will not only explain how much underpinning costs, but also what causes the structural movement in the first place.

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Row 0 - Cell 0 WorksLabour & Material (incl VAT)
Repairing CrackingRepair vertical cracks in brickwork to prevent further cracking Reinforcing rods to extend 500mm each side of crack. Rake out mortar joints and insert 6mm helical reinforcing rods, bonded with masonry grout; repoint to match existing£400/m length
Row 2 - Cell 0 Repair cracks in brickwork (one brick thick) including cutting out bricks and replacing with new, and pointing to match existing£87/m length
Row 3 - Cell 0 Cut out defective facing bricks and replace with matching new bricks, including pointing£17 (single brick)
Row 4 - Cell 0 Pointing up a crack or replacing a few bricksTypical costs around £300
Lintels and BeamsRenew defective 1,200mm-long timber lintel, remove old lintel and one course of bricks, fix new steel lintel and brick courses and make good£358 (in 265mm-wide cavity wall)
Row 6 - Cell 0 Fix new steel lintel 2,100mm long in prepared opening and make good£185 (in 265mm-wide cavity wall)
Row 7 - Cell 0 Remove defective brick arch, clean off bricks, prepare and rebuild arch, and point in mortar£163 (up to 1m long and half brick wide)
Cavity wall tie replacement Removal of say 200 defective wall ties, replacement and additioal ties, and allowing for scaffolding. (Add for repointing brickwork or re-rendering and making good disturbed plaster finishes)£4,500 (total)
Underpinning CostsFirst excavation of trenches down to base of existing foundations, say 1m deep£112/m²
Row 10 - Cell 0 Support sides of trench35/m length
Row 11 - Cell 0 Extra for breaking up 150mm-thick concrete bed£20/m²
Row 12 - Cell 0 Second excavation below level of existing foundations (say 1m deep)£109/m³
Row 13 - Cell 0 Support to sides of trench (second excavation)£37/m length
Row 14 - Cell 0 Cutting away existing foundations (projecting concrete 300mm wide x 300mm deep)£57/m length
Row 15 - Cell 0 Concrete underpinning: plain concrete (1:3:6 with 20mm aggregate) filled into form work in foundation trenches, 150–300mm thick£335/m³
Row 16 - Cell 0 Typical ballpark cost for underpinning an average house£10,000 to £15,000
Ian Rock

Chartered surveyor Ian Rock MRICS is a director is Rightsurvey.co.uk and the author of eight popular Haynes House Manuals, including the Home Extension Manual, the Self Build Manual and Period Property Manual.

Ian is also the founder of Zennor Consultants. In addition to providing house surveys, Zennor Consultants provide professional guidance on property refurbishment and maintenance as well as advising on the design and construction of home extensions and loft conversions, including planning and Building Regulations compliance.

Ian has recently added a 100m2 extension to his home; he designed and project managed the build and completed much of the interior fit-out on a DIY basis.