Prepare one brief before requesting three prices
Give each builder the same drawing revision, schedule of work, product specification, access information and expected completion scope. Include waste removal, making good, testing and documents. Identify owner-supplied products and say who installs and checks them. If the design changes during tendering, issue the change to everyone before comparing returns.
Ask bidders to mark every exclusion and assumption, rather than filling gaps silently. A low price can mean a useful efficiency, a narrower specification or a large unresolved risk. A useful comparison explains which it is. For substantial or technically complex work, an appropriately appointed designer or quantity surveyor can help assess scope and tender qualifications.
Understand what kind of promise you have received
Citizens Advice’s England guidance describes a quote as an agreed fixed price for the defined work and an estimate as an approximate indication. It also identifies circumstances in which more may be payable, including agreed extra work and a genuine pricing mistake. Do not reduce that guidance to “the word quote means the total can never change”. The accepted documents and terms matter.
| Term | What to establish |
|---|---|
| Fixed quotation | Exact included scope, exclusions, validity and adjustment terms |
| Estimate | Basis, range of uncertainty and when a firmer price will be available |
| Provisional sum | What anticipated work is unresolved and how it will be valued |
| Product allowance or PC sum | What supply amount covers, and whether fitting, waste and mark-up are separate |
| Daywork or rate | Hours, records, materials, mark-ups and authority to exceed a limit |
A document can combine fixed work and provisional sums. Ask the builder to label the parts. A headline “fixed price” should not conceal a substantial unidentified services allowance. Nor should you treat an omitted item as a zero-cost inclusion.
Make provisional sums specific enough to manage
RICS NRM 2, section 2.5.5, distinguishes defined and undefined provisional work in formal measurement. That convention helps explain why information matters, but it does not automatically become the terms of every domestic contract. Ask which rules your proposed contract actually incorporates.
For each provisional sum, record the nature and location of work, assumed quantities, what investigation or design is missing and when it will be resolved. Agree how the original sum is removed, how actual work is valued, which overhead/profit or attendance applies and how programme effects are addressed. Confirm whether the displayed amount includes VAT. A provisional sum is not a guaranteed ceiling unless the parties expressly agree an enforceable cap and its scope.
Normalise scope without pretending to rewrite the offers
| Line | A | B | C |
|---|---|---|---|
| Quoted net headline | 24,000 | 25,500 | 27,500 |
| Remove original provisional sum | −2,000 | −3,500 | 0 |
| Insert common net scope allowance | 3,500 | 3,500 | 0 |
| Add omitted disposal allowance | 1,500 | 0 | 0 |
| Add omitted decoration allowance | 0 | 900 | 0 |
| Comparable net forecast | 27,000 | 26,400 | 27,500 |
| VAT at 20% on comparable forecast | 5,400 | 5,280 | 5,500 |
| Comparable gross forecast | 32,400 | 31,680 | 33,000 |
A looked £1,500 cheaper than B in the net headlines, but the normalised gross forecast is £720 higher. B still has provisional work, while C’s equivalent work is fixed under the stated example. The comparison does not establish that B is the best contractor or guarantee any final sum. Obtain revised offers for the common scope, then assess quality, risk, programme and contract together.
Separate a comparison allowance from a contract adjustment
Assume a signed contract already includes a £2,000 net provisional sum. Its agreed replacement work is £2,600 net, and the contract expressly adds 10% to the net adjustment for overhead and profit. The difference is £600, the mark-up £60 and the net increase £660. At 20% VAT the gross increase is £792. Record the actual contract’s rule rather than adopting this illustrative percentage.
If the original sum already included mark-up or the contract prices the whole replacement differently, the calculation changes. Ask for the valuation and supporting scope before approval. Do not add the full £2,600 while leaving the £2,000 in the total, or add VAT again to a gross allowance. HMRC’s building VAT guidance is the tax reference; the contractor should state the basis of their own invoice.
Compare the delivery and payment terms
A full tender comparison includes start assumptions, duration, selection deadlines, supervision, subcontracting, access, insurance and payment triggers. Check whether professional design or contract administration sits outside the builder’s offer. Read warranty coverage and exclusions, including what happens if a product supplied by the homeowner fails.
FMB’s builder-selection guide recommends verification alongside like-for-like written quotations. Check recent comparable projects and the actual contracting business. Membership, references and insurance contribute different information; none changes an incomplete scope into a complete one. Ask who will be on site and who has authority to agree a variation.
Resolve the uncertainty that changes the decision
- List the omissions and provisional items with their reason and potential consequence.
- Ask whether survey, opening-up or a design decision can resolve each before appointment.
- Request revised written prices with the same specification and VAT basis.
- Read the proposed contract’s change, delay, payment and dispute terms.
- Accept only when you understand both the agreed commitment and the remaining exposure.
If a bidder cannot yet price concealed work reliably, a defined investigation may be more useful than forcing a guessed fixed amount. Set a limited initial instruction with a deliverable and decision point. Do not let exploratory work become open-ended authorisation for the entire refurbishment.
Questions for the builder’s clarification meeting
- Which drawings, schedule and product specifications does this offer follow?
- Which lines are fixed, provisional, excluded or owner-supplied?
- What does each allowance cover, including fitting and mark-up?
- How will an allowance be credited and replaced?
- Which events can change the agreed sum or completion date?
- What evidence triggers each payment, and who checks it?
- How are defects, disagreements and final documents handled?
Keep every clarification attached to the version you accept. Citizens Advice explains that evidence of what was agreed matters when a dispute arises. Keeping comparison notes in Reno Pro can help you organise the offers and accepted changes, but it does not choose the contractual risk allocation for you. The aim is an informed appointment, not simply the smallest number in the first row.
Sources, date and jurisdiction
- Citizens Advice — Before you get work done on your home — England
- FMB — How to choose a trusted builder
- RICS — NRM 2: detailed measurement for building works
- HMRC / GOV.UK — VAT for builders: houses and flats
- Citizens Advice — Problems with building work — England
Sources checked on 18 October 2026. Legal, approvals and contractual explanations in this article concern England. Check separately for Scotland, Wales or Northern Ireland. Prices are GBP; worked figures are editorial teaching examples for the stated scope and location, not market averages, contractor quotations or required reserves. Tax assumptions are stated beside each example.