How to Compare Contractor Estimates: A UK Homeowner's Step-by-Step Method

Three builders walk the same kitchen and come back with £8,400, £13,900 and £21,000. Nobody is lying. They have each priced a different job, because nobody told them precisely what the job was. Until you fix that you are not comparing prices, you are comparing assumptions — and the cheapest set of assumptions is usually the one that missed the most.

The comparison is won before the first firm arrives. Below: the paperwork you need, seven passes over each document, and the UK checks that separate a real price from a hopeful one. Not chosen who to invite? Start with how to hire a contractor.

These words mean genuinely different things in UK trade usage, and the one at the top of the page matters more than the number at the bottom. Note too that a contract signed in your own home falls under the Consumer Contracts Regulations 2013: 14 days to cancel, extended by up to twelve months if the trader never put that right in writing.

• •Estimate — indicative. Expect 10-20% of movement; use it to shortlist, nothing more.
• •Quotation — a firm offer that becomes the contract price on acceptance. Changes only by written variation, agreed before the work.
• •Tender — a priced response to a document you issued. Only tenders compare line by line.
• •Day rate plus materials — not a price. Fine for repairs, dangerous for projects; ask for a not-to-exceed figure.

The highest-return hour in any renovation is spent writing a schedule of works: a plain-English list of every task in sequence, with the specification and who supplies what. Give the identical document to all three firms and their prices stop being opinions about scope.

• •A schedule of works, one line per task with dimensions and finish ('lift 2.4m x 3.1m vinyl, latex screed, fit supplied LVT').
• •A measured floor plan, even hand-drawn, plus photographs of anything awkward.
• •A written specification for whatever you care about — boiler model, tile, taps, paint sheen, socket positions — plus who buys it.
• •Access notes: parking, working hours, whether you are living in, and who pays the skip licence (£30-£100 if it stands on the highway).
• •A spreadsheet with identical rows for each quote, and the questions to ask a contractor printed for the site visit.

Allow four to six hours of your own time across two to three weeks. Three usable quotes take three to five weeks from first enquiry; the firm who can start on Monday is usually free for a reason.

• •Schedule of works from a building surveyor: £450-£1,200 for a domestic refurbishment.
• •Architect's tender pack plus quote analysis: £1,500-£4,000 on a typical extension.
• •Quantity surveyor reviewing three tenders: £400-£900 for a half-day.
• •Structural engineer's calculations, without which nobody prices steels honestly: £450-£900.
• •Pre-contract paperwork costs 1-3% of the build and routinely saves 5-15% — see how to budget for a home renovation.

Print everything; screens hide omissions, paper and a highlighter do not. Work through all three documents one pass at a time rather than reading each end to end.

• •1. Level the scope. Tick every line of your schedule against each quote. Anything absent is not a saving — it is a variation priced later, when you have no leverage.
• •2. Split labour from materials. On refurbishment, labour lands at 50-65% of the total; 80% materials means the graft is under-priced.
• •3. Find the preliminaries: skips (£220-£350 for an eight-yard skip), scaffolding (£700-£1,400 for a two-storey rear elevation over six weeks), welfare, floor protection. Prelims run 8-15% of contract value; no prelims line means they are buried or forgotten.
• •4. Interrogate provisional and prime cost sums. 'Provisional sum: electrics £3,000' is a placeholder, not a price. Convert as many as you can into fixed items before signing.
• •5. Settle VAT in writing: £20,000 plus VAT is £24,000. Ask whether the firm is registered (compulsory above £90,000 turnover) and whether the reduced 5% rate applies — it can on a home empty two years or more.
• •6. Price the programme and payments: stages tied to completed work not calendar dates, a deposit of no more than 10-25% against ordered materials, and 2.5-5% retention held three to six months against snagging.
• •7. Verify cover yourself: £2m public liability minimum (£5m with scaffolding or structural work), £5m employers' liability if they have staff, and any Gas Safe number checked on the official register — see contractor red flags to avoid.

A quote that ignores the regulatory side is not cheaper, it is incomplete. In England and Wales, notifiable work under Part P — new circuits, a consumer unit replacement, anything in a room with a bath or shower — must be self-certified by an installer registered with NICEIC, NAPIT or similar, or notified to building control before work starts. Gas work needs a Gas Safe engineer whose card lists that category; Scotland runs building warrants.

Discard one American idea entirely: the lien waiver. There is no mechanics' lien over a private home here, so nothing to waive. Keep payment behind completed work, hold a retention, and pay over £100 by credit card — Section 75 of the Consumer Credit Act 1974 makes the issuer equally liable if the firm folds.

• •Building control: full plans or building notice, £300-£1,000+ domestically, plus the completion certificate a buyer's solicitor will demand. See when do you need a building permit for permitted development limits.
• •Party Wall etc. Act 1996: two months' notice for party structure work, one month for excavation within three metres of a neighbour's foundations. Surveyor fees if they dissent: £900-£2,000 per neighbour.
• •Landlords: annual gas safety check, and in England an EICR every five years — schedule these around the works, not after.
• •Leaseholders: where works cost any one leaseholder over £250, the freeholder must run a Section 20 consultation and obtain at least two estimates. Comparing quotes becomes a legal duty.

• •One quote 40% below the rest: nine times in ten an entire trade is missing. Count the trades in the breakdown.
• •One 40% above: often the honest price, built on a real sub-contract chain. Occasionally a polite 'go away' figure.
• •Round numbers throughout — £15,000, £8,000: nobody measured. Ask for the take-off.
• •'Price on application' against a key element: unpriced risk that becomes yours on signature.
• •Refusal to break the figure down at all: walk away, whatever the total says.

Amateur comparison stops paying once contract value passes roughly £40,000, when the job involves steels or underpinning, or when the quotes disagree about whether something is structural at all. A half-day quantity surveyor review at £400-£900 regularly finds five figures of difference in scope.

Whoever wins, put it on a proper written contract rather than an accepted quotation and a handshake — the JCT Building Contract for a Home Owner/Occupier or the Federation of Master Builders equivalent both work. Run through our home renovation contract checklist before signing, and keep every variation in writing.