What to Look for in a Builder's Quote (And Red Flags to Walk Away From) — UK 2026

A builder's quote tells you almost everything you need to know about whether they'll deliver your project well or badly. A thorough, professional quote means a professional build. A vague one-page lump sum means problems coming. Here are the eight things to look for in a builder's quote — and the seven red flags that should make you walk away.

The 8 things a good builder's quote always includes

1. Full breakdown by trade/stage

A professional quote breaks down cost by trade and stage of work. For an extension, that means separate lines for:

• Strip out and waste removal
• Foundations and groundworks
• Brickwork / blockwork
• Structural steels and supply
• Roof structure and weather envelope
• Glazing (windows, bi-folds, skylights)
• First-fix electrical
• First-fix plumbing
• Plastering
• Second-fix electrical
• Second-fix plumbing
• Decoration
• Flooring
• Building Control and Party Wall fees
• VAT

Each line should have a £ value. You should be able to see where the money goes. If a quote arrives as 'extension build: £55,000' with no further detail, that's a problem.

2. Specifications for major items

The quote should reference the spec of major items:

• Doors and windows (manufacturer, model, glazing spec)
• Roof covering (type, manufacturer)
• Kitchen (cabinet manufacturer, worktop material)
• Bathroom (suite spec, tile spec)
• Heating (boiler model, radiator type)
• Floor finish (type, thickness, manufacturer)

Without this, what counts as 'a kitchen' could be a £3,000 budget install or a £25,000 premium build. Lock the spec at quote stage so there's no ambiguity later.

3. Exclusions clearly listed

What's NOT included is as important as what is. Common exclusions to look for:

• Furniture and white goods
• Light fittings (unless specifically included with spec)
• Window treatments (blinds, curtains)
• Garden/landscaping reinstatement
• Skip/waste disposal beyond a stated quantity
• Building Control fees (if not separately listed)
• Party Wall surveyor fees
• Stamp duty / legal fees
• Decoration touch-ups after move-back-in

A good quote explicitly lists exclusions. A bad quote leaves them implicit, leading to disputes later.

4. Payment schedule

A reasonable payment schedule for a £50k extension:

• Deposit on contract signing: 10-15% (£5,000-7,500)
• Stage payment on foundations complete: 15-20% (£7,500-10,000)
• Stage payment on walls/roof watertight: 20-25% (£10,000-12,500)
• Stage payment on first-fix complete: 15-20% (£7,500-10,000)
• Stage payment on second-fix complete: 15-20% (£7,500-10,000)
• Final payment on completion: 10% (£5,000)
• Retention held back: 5% for snagging period (£2,500)

Each payment tied to a specific completed milestone — not just dates. Retention (typically 5%) held back for the snagging period and released after defects are fixed.

5. Timeline with key milestones

The quote should commit to:

• Site start date (after planning + Party Wall + Building Notice complete)
• Watertight envelope date (week X)
• First-fix complete date
• Practical completion date
• Liquidated damages provision for late completion (typically £200-500/week)
• Snagging period (typically 2-4 weeks post-completion)

6. VAT clearly shown

VAT is 20% on most residential construction. Quote should clearly show:

• Subtotal (net of VAT)
• VAT amount
• Total (inc VAT)

Some projects qualify for zero-rate VAT (new-build, listed building specific work, charities) — but standard residential extensions and renovations are full-rate. A quote that doesn't mention VAT is likely either: trading below VAT threshold (under £85k turnover, lower-end builder); or going to add it at the end as a 'surprise'.

7. Insurance and credentials

The quote (or accompanying documentation) should evidence:

• Public liability insurance — minimum £2m, ideally £5m+
• Contractor's all-risks insurance for the works
• Membership of relevant trade bodies (FMB, TrustMark, NICEIC for electrical, Gas Safe for gas)
• Company registration details (Companies House number, registered address)
• Years trading

8. Terms and conditions

Either the quote includes T&Cs or references a formal contract that will be signed (typically JCT Minor Works for residential projects up to £150k). The T&Cs cover:

• Variation procedure (how changes are agreed and priced)
• Defects liability period (usually 12 months)
• Dispute resolution mechanism
• Performance bond or parent company guarantee for larger projects
• Force majeure provisions

7 red flags that should make you walk away

1. Lump sum with no breakdown

A quote like 'Extension to rear: £45,000' with no further detail. You can't compare it to other quotes meaningfully, and you can't see where extras might be hidden. Either request a breakdown or look elsewhere.

2. Dramatically cheaper than others

If three quotes are £55-65k and one comes in at £35k for the same scope, the cheap one is almost always either: dropping quality (cheaper materials, less experienced labour), planning to add costs later (variations), or a builder in trouble (cash-flow desperate, will start your job then disappear mid-build). The £20k 'saving' often becomes a £40k loss.

3. Demands more than 25% upfront

A reasonable deposit is 10-15% on signing. Above 25% is a warning sign — either cash-flow problems, or planning to abscond. A builder that needs your money to buy materials for THIS job is a builder one bad job away from failure.

4. Cash-only or no VAT invoice

Cash-only is either trading below VAT threshold (which limits the size of the company and is fine for small jobs) OR not declaring income (illegal, you have no recourse if something goes wrong). Either way, a £40k+ project should be invoiced with VAT through a properly registered business.

5. Pressure to sign immediately

'Price only valid this week' / 'I have a slot opening up Monday — confirm by Friday or I'll fill it'. Pressure tactics are about preventing you from getting comparative quotes or due diligence. A confident builder is happy for you to take 1-2 weeks to compare.

6. Won't put anything in writing

Verbal quotes, handshake agreements, 'we'll figure it out as we go'. All warning signs. Any project over £5,000 should have a written quote and either written T&Cs or a formal contract. If a builder won't commit on paper, they're protecting themselves from future accountability — at your expense.

7. No physical business address

Mobile number only, no website, no business address, no Companies House registration. If something goes wrong, you have nowhere to serve legal notice. Even small one-man builders should have a registered trading address and business name.

Comparing multiple quotes — what to look for

Get at least 3 quotes for any project over £10k. When comparing:

• Compare like-for-like spec — different builders might quote different materials or scope. Normalise before comparing prices.
• Look for outliers — the cheapest 30%+ below the others is suspicious; the most expensive 30%+ above is also worth questioning
• Ask why for differences — a good builder will explain what's included that another's quote isn't
• Check references — speak to 2-3 recent clients of each builder
• Visit recent completed work — not just photos, actual site visits where possible
• Check Companies House — see how long they've traded, any director changes, recent accounts

Beyond the quote — the contract

For any project over £15k, insist on a formal written contract (not just a quote). JCT Minor Works contracts are the residential standard for £25-150k projects. They cover:

• Scope of work (referenced to drawings and spec)
• Contract sum (and how variations are priced)
• Completion date and liquidated damages
• Payment schedule
• Retention
• Defects liability period
• Insurance requirements for both parties
• Dispute resolution

Cost: JCT contracts are free to download from RIBA Bookshop. Take an hour to read it before signing. Solicitor review is worth £200-400 on a £50k+ project.

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