What a kitchen extension actually costs in 2026

You've done the site visit. The client wants a 30 square metre extension off the back of a Victorian terrace in Reading. Bifolds, vaulted ceiling, kitchen island, the lot. They're asking for a quote by Friday. What's the number?

The honest answer, before you've even costed materials: somewhere between £52,500 and £70,500. That's the range published by quantity surveyor Tim Phillips for Homebuilding & Renovating in 2025 — £1,750 to £2,350 per square metre of new internal space, before VAT, design fees, structural engineer, planning, building control, external works, contingency or preliminaries.

Read that list of exclusions again. That's where the money leaks.

Where the £18,000 spread comes from

Two builders quote the same job. One comes in at £52k, the other at £70k. Same brick, same span, same client. The difference isn't greed. It's the bits that get forgotten.

The £52k quote almost always assumes nothing surprising behind the wall. No party wall agreement. No service diversion. No structural beam upgrade. The client signs because it's the cheaper number. The builder absorbs the variations on his own margin because by the time he's discovered the cast iron drain, he's already broken ground and the conversation is too awkward to have.

The £70k quote prices in the contingency. It looks expensive on paper. The builder loses the job to the cheaper quote half the time, and the client phones him in tears six months later when the £52k quote has crept past £80k.

Neither builder wins. The honest answer is to itemise everything — including the contingency — and let the client see why one number is bigger than the other.

The five line items most quotes forget

From the quotes we've seen tradespeople rebuild in BuilderBro, the same five line items keep getting missed:

• Party wall surveyor — £900 to £1,800 if neighbours don't consent quickly. Most domestic extensions in terraces or semis trigger the Party Wall Act 1996. Build it in.
• Structural engineer — £750 to £1,500 for steel calcs on any extension over 3 metres deep. The client thinks the architect handles this. Often they don't.
• Building Control fees — £600 to £1,200 for a standard single-storey extension in 2026. Council fees went up again in April. Check your local authority's published schedule, don't guess from last year's job.
• Skip and spoil removal — £400 to £900 per skip, three to six skips on a typical kitchen extension. Tipping fees are tracked properly now under hazardous waste rules.
• Reinstating the existing kitchen room — re-plastering, re-flooring, redecorating where the new opening meets the old wall. Five grand, easy, and almost no quote includes it as a separate line.

That's £8,000 to £15,000 of work that ends up on the builder's tab if the quote doesn't list it. On a £52k headline price, that's your entire margin gone.

The same problem, across the pond

This isn't a UK quirk. The 2024 Cost vs Value report from Remodeling magazine — the most cited US contractor benchmark — pegs an upscale midrange minor kitchen remodel in the United States at around $27,000, with a major remodel running $80,000 to $160,000 depending on region. Atlanta builders quote it at one number; San Francisco builders quote roughly twice that for the same scope. The spread is the same as ours: it's not the bricks and the wood, it's the fees, the permits, the contingency, and the things the homeowner didn't tell you about.

One Boston general contractor we spoke to last winter — Mark Donovan, who runs a four-man crew out of Quincy, Massachusetts — told us he started winning more bids the year he stopped competing on the headline number and started showing every line item with a one-line note explaining what it was. His close rate on quotes over $50,000 went from roughly one in five to one in three. Same prices. Different quote.

What to do about it

Two changes will make a £60k quote more likely to win, and more likely to be profitable when it does:

First, itemise to the line. Don't bury the party wall surveyor inside "professional fees". Don't roll the skips into "site costs". Show the client every cost as its own line, with a one-sentence explanation. Clients aren't trying to trip you up — they just don't know what they don't know. A clear quote builds trust faster than a low number.

Second, quote in stages. Deposit on signature. Stage payment at strip-out. Stage payment at first fix. Stage payment at second fix. Final on handover. You don't have to fund the client's project out of your own bank account, and they don't have to write a £70,000 cheque on day one.

The quote isn't a sales document. It's the start of a working relationship — and the client is reading it more carefully than you think.

Reading is one terrace. Bristol is another. Manchester another again. Build your quotes the same way every time, and the spread between what you quoted and what you billed will start to close.