The Short Answer
On our estimates, underpinning one wall of a house with traditional mass concrete costs about £6,000 to £21,000, from a small terrace to a large detached house, and takes three to six weeks. Mini-piling costs more and resin injection a little less. A structural engineer has to be involved, and an inspection costs £200 to £2,000.
Most cracked houses don't need underpinning: the Association of British Insurers says only rarely are cracks caused by subsidence, and even then underpinning is for the extreme cases. If you think it's subsidence, call your buildings insurer before you pay anyone.
Underpinning prices by method
| Method | One wall, terrace to detached |
|---|---|
| Mass concrete | £6,000 to £21,000 |
| Mini-piling | £10,500 to £36,500 |
| Resin injection | £4,800 to £17,000 |
Mass concrete is the slowest method, because the concrete has to cure between each stage of digging. Resin injection can be done in days and avoids deep digging, and may suit older houses with shallow foundations; mini-piling sits in between. The engineer decides which suits your ground.
Is it subsidence?
The ABI says subsidence cracks tend to:
- appear suddenly, especially after long dry spells;
- be diagonal and wider at the top than the bottom;
- be thicker than a 10p coin;
- show up around doors and windows, often with doors and windows sticking.
Cracks from a house shrinking and swelling with the seasons, a new extension settling or fresh plaster drying are usually even in width and from hairline to 3mm, and can be filled when you redecorate. The common causes of real subsidence are clay soil drying out, trees and shrubs close to the house, leaking drains and old mine workings.
Subsidence and your insurance
Building regulations and party walls
Underpinning is "building work" under the Building Regulations, so it needs building control approval. On a semi or terrace, digging within 3m of a neighbour's building and below its foundations (or within 6m, depending on depth) needs a party wall notice at least 1 month before you start.
Building an extension? New foundations are covered on groundworks costs.
Buying a house that's been underpinned
The ABI says homeowners often find insurance harder or dearer to get after a subsidence claim, with higher premiums or different terms, and suggests a specialist broker through the British Insurance Brokers' Association. Before buying, I'd want the engineer's report, the building control sign-off for the underpinning, and a quote for the buildings insurance.
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Frequently asked questions
How much does underpinning cost?
On our estimates, about £6,000 to £21,000 for one wall with mass concrete, £10,500 to £36,500 with mini-piling and £4,800 to £17,000 with resin injection.
Is underpinning a big job?
Yes. Mass concrete underpinning of one wall takes three to six weeks, needs a structural engineer and building control approval, and often a party wall notice. Resin injection is quicker, often a matter of days.
What are the disadvantages of underpinning?
Cost, disruption and time, and it doesn't fix the cause on its own: drains, trees or clay drying out still need dealing with. Insurance can also be harder or dearer to get after a subsidence claim.
Is it worth buying a house that needs underpinning?
Only with the facts: an engineer's report on the cause, a price for the work, and a buildings insurance quote. If it's already been underpinned, ask for the building control sign-off.
Is underpinning covered by insurance?
Often, if it's needed because of subsidence and your buildings policy covers it. The ABI says most policies have a subsidence excess of around £1,000. Tell your insurer before commissioning any work.
Does underpinning need a party wall notice?
Usually, on a semi or terrace: digging within 3m of a neighbour's building to below its foundations needs notice at least 1 month before.
How we priced thisView sources (5, 2 official)
Rules come from the legislation and official guidance, read at source. Prices are our estimates: we check them against trade price data, retailer shelf prices and specialists' price lists, then build them up from their parts so the totals add up. Below are the sources behind the page; the trade price guides we only compare against aren’t listed. Where sources disagreed, we've said so. More on our method.
- OfficialThe Building Regulations 2010, regulation 3: meaning of building work, legislation.gov.uk. Checked 15 Oct 2026.
- OfficialParty Wall etc. Act 1996, sections 2 and 3, legislation.gov.uk. Checked 15 Oct 2026.
- IndustrySubsidence, Association of British Insurers. Checked 15 Oct 2026.
- IndustryWhat to do if subsidence happens, Association of British Insurers. Checked 15 Oct 2026.
- IndustryGetting insurance after a subsidence claim, Association of British Insurers. Checked 15 Oct 2026.
