How Much Does Underpinning Cost?

£1,000 to £2,500 per bay for traditional mass concrete, and a bay is roughly a metre of wall. Most domestic schemes are one corner or one elevation rather than a whole house, so the commonest job lands between £7,000 and £18,000 once the engineer, the surveys and the Building Control charge are counted in.

The unit is the part worth arguing about. Underpinning is designed, programmed and inspected bay by bay, so a quotation you can check is one that tells you how many bays there are and how deep each goes. How the work is done, and why it goes in numbered bays, is the background to every figure here.

Why a bay is the unit, and a square metre is not

Rate cards quote per square metre because it is easy to publish, not because anybody builds that way.

A bay is a single pit dug tight against the wall, taken below the existing footing to the level the engineer specified and filled with concrete. It is commonly around a metre wide. The sequence drawing numbers each one, and no two adjacent bays are ever open at once, so the bay count is the count of digs, the count of pours and most of the labour.

Published rates of roughly £1,500 to £2,600 per square metre are the same money expressed differently, and they hide the variable that moves it. Two walls of identical length can differ by half again because one needs bays to 1.2 metres and the other needs them to 2.4. Ask for the bay count and the design depth, then multiply. A quotation that gives you neither has not been priced off a design.

What depth does to the number

Depth costs twice: once in what comes out, and again in holding the sides up while it does.

A shallow bay is a day’s digging and a few barrows of concrete. Take the same bay to two and a half metres and there is more than double the spoil, timber shoring to keep the pit safe, a much longer lift out by hand, and considerably more concrete. That is the whole journey from the bottom of the per-bay range to the top of it, and the trial hole settles it rather than the quotation.

Somewhere around three metres, hand digging stops being sensible and the scheme changes shape rather than getting dearer by degrees. Piled and beam work is generally quoted at £1,500 to £3,000 per linear metre of wall, and screw piles at £2,000 to £4,000 per pile with the spacing set by the design. So the depth of the competent stratum is the most useful thing to establish before you budget anything. Near a mature tree on shrinkable clay it is often deeper than people hope, and why the ground behaves that way here explains what sets it.

What access does to it

Nothing about this work is mechanised, and the route to the wall is a real line in the price.

Spoil leaves by barrow, because no machine reaches under a wall. Where the affected elevation is at the back of a terrace with no side gate, every barrow goes through the house on boards, and that alone can add a third to the labour against the same wall on an open drive. A piling rig has its own version of the problem: it needs headroom and a route in, and a rear garden reached through a hallway has neither, which pushes the design towards a cantilever arrangement worked from one side at a higher rate.

The costs that are not in the builder’s price

On an owner led job these are yours, and together they are rarely less than a fifth of the total.

• Structural engineer. Around £800 for a straightforward single elevation investigation and design, and £2,500 or more where several elevations are involved or the diagnosis is contested.
• Drain survey. £150 to £300 for a domestic camera survey, worth doing early because a leaking drain is a far cheaper cause to deal with than the ground is.
• Monitoring. Level readings across a full seasonal cycle before the design is fixed, and often a further period afterwards to confirm the movement has stopped.
• Building Control. Full plans rather than a building notice, because the sequence has to be approved and the pits seen before concrete goes in. Budget in the region of £300 to £750, and see what those charges are made up of.
• Party wall. On a semi or a terrace this is close to unavoidable, and where the neighbour appoints their own surveyor you pay for both. What surveyors charge is set out separately. So is which notices foundation work actually triggers.

Insurer led and owner led are different figures

Same concrete, two completely different sums leaving your account.

Where an insurer accepts a subsidence claim, what you pay is the excess. Subsidence carries its own excess, set well above the general one on the policy, and £1,000 is the figure most household policies use. Against a scheme costing five or ten times that, the arithmetic is obvious. What you give up is control: you do not appoint the engineer, you generally do not choose the contractor, and the design is written to remedy the defect rather than to suit anything you were planning to build.

An owner led scheme is the reverse. Nothing has gone wrong, the underpinning is enabling work for a cellar or a storey over a garage, and it sits inside the build contract like the steels. You pay all of it, you appoint everybody, and no claim is recorded against the address afterwards. That cost is usually absorbed into the wider project, and what a cellar conversion involves shows where it falls.

The expensive mistake sits between the two. Claiming for movement that turns out to be a defect in recent building work puts a subsidence record on a house that does not have subsidence, and that record follows the property rather than you.

What the quotation will not include

Making good is a separate line, because the concrete does not close a crack. So are redecoration, the paving or planting that came out to reach the wall, drain repairs, tree work where a protected tree is involved, and VAT. The engineer’s certificate of structural adequacy is normally inside the design fee, and it is worth confirming that it is, because it is the document a future buyer’s surveyor asks to see.

Getting to a real figure

Take the design depth from the trial hole, the bay count from the sequence drawing, and price the fixed items separately from the rate. A quotation written without a hole in the ground is an estimate with the risk parked on you, and here the risk is the entire distance between the two ends of the range.

Where underpinning is enabling work rather than a repair, we survey the existing footing before pricing anything, and the survey and the quotation cost nothing. How it sits alongside everything else on a build is on the extension costs page.

These figures are indicative for the Colchester area at the review date below. Foundation design and the extent of any underpinning are matters for a structural engineer on your own property, so use them to sense check a quotation rather than as one.

Last reviewed August 2026.