How much does underpinning cost in London?

Published UK guides put mass concrete underpinning at £1,250–£2,500 per linear metre of wall and beam-and-base or mini-piled underpinning at £1,500–£2,600 per metre, though the sources mix per-metre and per-square-metre units, so the rate only means something with the unit stated. The one London figure we could trace is about £1,500 per metre run for mass concrete pins to a metre deep, excluding VAT. No source in this set publishes a London uplift for underpinning, so we have not applied one.

The published worked examples put mass concrete underpinning of a single four-metre wall on a two-bedroom terrace at about £6,000, a three-bedroom semi at £13,500 and a four-bedroom detached house at £21,000, which is where the typical £6,000–£25,000 subsidence range comes from. Underpinning a whole London terrace to basement depth is a different job, which two London basement guides put at £35,000–£65,000 where their ranges overlap. The length of wall affected and the depth to good ground decide which of those you are looking at.

Yes. Underpinning alters the foundations, so it is controlled work under the Building Regulations. Building control is notified before the start, inspects the pits at the stages the engineer's design sets out, and issues a completion certificate at the end, which is the document a buyer's solicitor and an insurer will ask for. Hillingdon publishes a charge of £744 including VAT for underpinning up to six metres; other London boroughs charge by the estimated cost of the work.

Yes. An engineer establishes whether the movement is progressive, what caused it and how deep the stable ground is, then designs the scheme: the method, the depth, the length of wall and the sequence the pits are dug in. Building control inspects against that design and the party wall surveyors read it. Where the work is an insurance claim the insurer appoints the engineer; otherwise our engineer's design is part of the job, so the person who designed the pits is on the same contract as the crew digging them.

Often, yes. Most London subsidence is caused by clay shrinking around tree roots or by a leaking drain, and dealing with the cause, by reducing or removing the tree, installing a root barrier or repairing the drain, can stop the movement on its own, which is why insurers monitor a crack for months before agreeing to underpin. Underpinning is the answer when the ground under the footing cannot be made stable any other way. An engineer's investigation, not a builder's quote, is what decides.

Treating the cause first: drain repair, tree management and a root barrier. Where the foundation itself has to be dealt with, the alternatives to traditional mass concrete are mini-piled or beam-and-base systems, which reach deeper ground with less digging, and resin injection, which fills and compacts the ground beneath the footing rather than extending it and suits some soils and not others. Each is priced per case rather than per metre in the published guides, and the engineer's investigation decides which is appropriate.

Usually, provided the paperwork exists. Properly underpinned foundations are more stable than the ones around them, and what a buyer needs is the engineer's design, the building control completion certificate, any guarantee from the contractor or insurer, and the claim history so the buildings insurer can be told. The problems come with undocumented work, an unresolved cause such as the tree still in the garden, and insurers who raise the price of cover or add a subsidence exclusion. Ask for the file before you make an offer.

A seller has to answer the buyer's pre-contract enquiries honestly, and those ask about structural repairs, subsidence and insurance claims, so underpinning has to be disclosed when asked. Insurers ask the same question when you take out or renew a policy, and an answer that turns out to be wrong can void the cover. The practical approach is to keep the engineer's report, the completion certificate and any guarantee together and hand them over, because documented underpinning is far easier to sell than a rumour of it.

Generally yes, with conditions. Lenders and insurers ask for the engineer's report, the building control certificate and any guarantee, and want to see that the cause was dealt with. Some mainstream insurers will cover a previously underpinned house at a normal price once the paperwork is in order; others add a higher subsidence excess or refer it to a specialist. It is worth getting quotes before you exchange rather than after, because the answer varies more between insurers than between houses.

Not sensibly. Underpinning removes the ground from beneath a wall that is already moving, in pits whose size and sequence are designed so the wall is never unsupported for longer than it can stand, and a pit dug in the wrong place or left open too long brings the wall down. It is controlled by the Building Regulations, usually triggers the Party Wall Act, and an insurer will not pay for or cover work it did not approve. The digging looks simple; the engineering that decides where and when is the job.

From published cost guides accessed in September 2026: MyJobQuote, Zapperty, Mainmark and Fibrwrap CCUK for the national per-metre and per-project ranges, EMA Structures for the London per-metre point, TB&D Construction and TrustBuilt Projects for London basement-depth underpinning, and G8 Builds for London piling. We took the median of the published lows and highs where there were enough sources and the overlap where there were two, and rounded to the nearest fifty pounds per metre or thousand pounds per project. They are market ranges, not MO Team quotes.