7 Red Flags in a Builder's Quote You Should Never Ignore
The cheapest quote almost never wins. In 2026, a UK kitchen extension is typically landing between £45,000 and £72,000 depending on county and finish — and the three or four quotes you collect for a job that size will not all be honest. There are seven specific builder quote red flags that predict trouble before you have signed anything.
Trust a builder's quote when it is itemised, written on company-headed paper, references your specification line by line, includes a stage-by-stage payment schedule, and asks for no more than around 10% as a deposit. Mistrust it when any of the seven warning signs below appear — none is fatal on its own, but two or three together is a strong signal to walk away or at least re-quote elsewhere before you commit. The cost of finding out the hard way is usually six to twelve months of stress and several thousand pounds you will not recover.
- A single lump-sum total with no itemised breakdown
"Total: £58,000" is not a quote, it is a number. A real quote breaks the job down into labour days, materials by category, plant hire, scaffolding, skip hire, kitchen or bathroom supply, and the builder's margin and overheads. Without that breakdown, scope creep is invisible: every extra socket becomes a variation you cannot challenge because you never knew what was in the price to begin with. Insist the spec maps line by line to your brief, and ask for a separate provisional-sums list (see flag 4).
- A deposit that is bigger than the work done so far
A reasonable deposit on a £40,000-plus job is around 5% to 10% to confirm the slot, with one-off bespoke material orders (windows, structural steels, custom kitchens) sometimes paid for separately on a back-to-back basis. If a builder asks for 30%, 40% or 50% upfront on day one, you are paying for someone else's overdraft. Established trades pay their suppliers on 30-day terms, so they should not need your cash before they have even unloaded the van. Insist on a payment schedule tied to staged completion — strip-out, slab, first fix, second fix, snagging — with a clear figure against each stage.
- No written contract — "we'll sort it as we go"
A handshake is fine in the pub. It is not fine on a £60,000 extension. A proper contract sets out start and longstop dates, the specification, the materials list, the payment schedule, what counts as a variation, who insures the works, and how disputes are resolved. The JCT Homeowner Contract and the Federation of Master Builders' Domestic Building Contract are the two templates most UK refurbishments use; both are inexpensive and well known to any serious builder. A refusal to sign either is a refusal to be held to a fixed price once the job has started.
- Provisional sums stacked everywhere
A provisional sum is a placeholder inserted into the quote because something is not yet specified — typically the kitchen, the staircase, or specialist joinery. One or two is normal. Twelve is not. Every provisional sum is a future invoice you cannot control, because by the time the spec is pinned down the builder is on site and your leverage is gone. A trustworthy quote pins materials down by brand and model, or sets a clear pound budget that you, the homeowner, will spend at your chosen supplier with the builder taking no margin on it.
- No proof of insurance, trade body membership or company details
A serious builder volunteers all of this on page one: company number, VAT number where applicable, registered office, public liability insurance of at least £2 million (£5 million for structural work), employer's liability insurance if they have staff, and at least one credible trade body — TrustMark, the Federation of Master Builders, the National Federation of Builders, or Chartered Institute of Building (MCIOB) membership for the principal. Sole traders are absolutely fine, but they need public liability insurance and a name you can find on Companies House. "I've been doing this thirty years" is not an insurance certificate.
- The quote is the cheapest by a wide margin
If you collect three quotes and one is 25% to 30% below the other two, the cheap one is almost always missing scope, underestimating materials, banking on variations once they are on site, inexperienced — or all four. Read it line by line against the others before you assume you have struck a deal. The scope will not match. A useful 2026 benchmark is to take the median of three comparable quotes and treat the cheapest as a starting point for a conversation, not a winner.
- No clear timeline, or "we can start next week"
Any UK builder with a credible reputation is booked 8 to 16 weeks out as of 2026. "We can start Monday" usually means there is a gap, and there is almost always a reason for the gap. A trustworthy quote includes a start date, a one-page programme of works (even a hand-drawn Gantt), and a longstop completion date. It also names the lead site manager and what happens if they are unavailable. Sub-contracting to "a chap we use" without naming the chap is a flag in its own right.
The neighbour-vouched-for trap
Most homeowners who get badly burned by a builder do not get burned by a stranger — they get burned by the cheapest of three quotes, paid in cash, with no written contract, from someone a neighbour vouched for. The single most expensive sentence in UK home renovation is "he did Pete's kitchen, he'll be fine". Word-of-mouth is a starting point, not a substitute for the seven checks above.
What to do in the next 30 minutes
• Open the most recent quote you have and tick off how many of the seven flags are present.
• If you only have one quote, queue up two more — same drawings, same spec, same materials list, all sent at the same time.
• Search the builder's company name on Companies House and on the TrustMark register.
• Ask the builder to email their public liability insurance certificate as a PDF (not a phone-camera screenshot).
• Save every quote, drawing and photo of the existing house in one folder so you can compare on a single screen.
Where Home+ and Trade Pilot fit
You do not have to chase three quotes alone. Trade Pilot puts your brief in front of three TrustMark-vetted local trades at once, so you can compare like-for-like instead of guessing why one is half the price. Compare 3 vetted quotes on Trade Pilot — and keep the drawings, photos and signed contract for every job in one place with a free Home+ account.
FAQ
How much should a builder's deposit be in 2026?
For most UK domestic refurbishment jobs, a deposit between 5% and 10% of the contract value is normal and reasonable, with large bespoke material orders (windows, structural steels, custom kitchens) paid for separately on a back-to-back basis where appropriate. Anything above 25% on day one is a red flag. The legal default in England and Wales gives you no automatic right to recover a deposit if the builder fails to start, so smaller is safer. A staged payment schedule tied to verifiable milestones matters more than the deposit figure itself.
Is a verbal quote legally binding in the UK?
In principle yes, but in practice it is almost impossible to enforce, because you have to prove what was agreed and when. Under the Consumer Rights Act 2015 you have rights against a trader for services to be performed with reasonable care and skill, but disputes over scope and price collapse very quickly without a written quote. Treat a verbal quote as a friendly indication; do not commit a deposit or any payment until you have the same numbers in writing on company letterhead with a clear specification attached.
What is the difference between an estimate and a quote?
An estimate is a best guess — it can move up or down once the work begins, and the law lets the builder revise it if their assumptions change. A quote is a firm price for a defined scope, and the builder is bound to it unless the scope itself changes (a true variation). For a renovation, you want a quote, not an estimate. If a document is titled "estimate", ask for it to be re-issued as a quote against a written spec, or expect to argue about the final invoice.
Should my builder be VAT-registered?
Any UK business with taxable turnover above the VAT threshold must register, so a serious refurbishment business almost always is. A non-VAT-registered builder is either a sole trader keeping the business deliberately small, or splitting work across two companies to stay under the threshold — the latter being a red flag of its own. If your contract value would push them well above the threshold and they are still not registered, you have a tax-status question to resolve before you sign.
