Getting a building quote is easy. Getting three accurate, comparable quotes that reflect the actual scope of work — and then choosing the right one — takes a little more preparation. Homeowners who skip the briefing stage almost always end up with quotes that cannot be meaningfully compared, leading to either an unpleasant surprise mid-project or the wrong contractor being chosen.
Why Most Quote Comparisons Go Wrong
The root problem is almost always an inadequate brief. If three builders are given a vague description of the work (“extend the kitchen into the garden”), each will make their own assumptions about:
- Specification of materials (concrete block vs. timber frame vs. SIPs)
- Quality of finishes (basic vs. mid-range vs. premium)
- What is and is not included (groundworks, drainage, making good, decoration)
- Programme length and therefore labour costs
The result is quotes that might vary by 40–60% not because one builder is cheaper than another, but because they have priced entirely different jobs. The only way to get genuinely comparable quotes is to give every contractor the same written brief.
Step 1: Prepare Your Brief
Before approaching any builder, prepare a written package. For most domestic projects this should include:
Drawings — even a simple sketch with dimensions helps. For anything involving structure or planning permission you will likely have architect or structural engineer drawings already. Share these.
A schedule of works — a numbered list of every item of work you want priced. This does not need to be a formal document; a clear Word document or spreadsheet is fine. The more specific the better:
“Supply and fit new 3m x 2m bathroom with customer-supplied sanitaryware, contractor to supply and tile with customer-approved ceramic tiles up to 1.8m, install extractor fan to Building Regs Part F requirements, new consumer unit fused spur for shaver socket.”
Specification notes — where the contractor is supplying materials, state the quality level (e.g. “mid-range engineered oak flooring, minimum 14mm wear layer” or “standard sand/cement render to external walls, painted finish”).
Programme requirements — your preferred start date and any constraints (you need the kitchen functional by a certain date, you are away for two weeks in August).
Access and site conditions — parking availability, hours of access, any complications (party walls, listed building consent, asbestos survey results).
Step 2: Who to Approach
Get a minimum of three quotes. More than five rarely adds value and wastes everyone’s time.
Sources of reputable builders:
- Personal recommendation — the most reliable. Ask neighbours, friends, and local estate agents who they have used recently.
- Federation of Master Builders (FMB) — members are vetted, insured, and subject to a code of practice. FMB also offers free dispute resolution.
- TrustMark — a government-endorsed quality scheme covering most trades.
- Local architect referrals — if you have an architect, ask for contractor recommendations; they will have direct experience of build quality.
Check before meeting any contractor:
- Public liability insurance (minimum £2m; £5m+ for larger projects)
- Employers’ liability insurance (legally required if they have employees)
- VAT registration (projects over roughly £150,000 in materials and labour may require the builder to be VAT registered)
- Any relevant trade membership or certification (Gas Safe, NICEIC, FENSA for relevant trades)
Step 3: The Site Visit
Invite each builder to carry out a site visit before they quote. A builder who quotes without visiting should ring alarm bells for anything other than very minor works. The site visit allows them to spot complications — a concrete floor that will need breaking up, a soil pipe in an awkward location — that will affect the price.
Use the visit to assess them as much as they are assessing the job. Key questions:
- Who will be on site day-to-day? (The owner, or a site manager, or subcontractors you have never met?)
- Who are their regular subcontractors for trades such as electrical and plumbing?
- Can they provide references and contact details for similar recent projects?
- What is their current programme and realistic start date?
Step 4: Reviewing the Quotes
When quotes arrive, compare them against the following framework:
| What to check | What to look for |
|---|---|
| Scope coverage | Does the quote address every item in your schedule of works? |
| Exclusions | What is explicitly excluded? (Decoration, skips, building control fees?) |
| Allowances | Are provisional sums and contingencies clearly labelled? |
| Materials | Is it clear who supplies what? Are materials specified or generic? |
| Programme | Start date, estimated duration, key milestones |
| Payment terms | Stage payments vs. monthly valuations; what triggers each payment |
| Warranties | Is any workmanship guarantee offered, and for how long? |
| VAT | Is VAT included or excluded? Check each quote is consistent |
Typical Cost Benchmarks (2026, UK excl. London)
| Project type | Typical range | Notes |
|---|---|---|
| Bathroom refit | £4,000–£12,000 | Excluding sanitaryware supply |
| Kitchen fit (excl. units) | £2,500–£6,000 | Labour only, units customer-supplied |
| Single-storey rear extension | £1,800–£2,800/m² | Including Building Regs, excl. fees |
| Loft conversion (dormer) | £45,000–£75,000 | Full turnkey inc. structural |
| Full house renovation | £600–£1,200/m² | Depending on specification |
London and the South East typically add 20–35% to these figures.
Step 5: The Lowest Quote Trap
The lowest quote is not always the best value. A price that is 25%+ below the other two almost always means one of:
- Items have been missed or excluded
- Cheaper materials are assumed
- The builder is buying the work and intends to recover margin through variations
- They are underpriced and may run into cash-flow problems mid-project
Equally, the highest quote is not automatically the best quality — it may simply reflect a busy contractor with a healthy order book.
The fairest approach is to select the quote that is most detailed, most complete, and from the contractor you trust most after references and the site visit. Price is a factor, but it should not be the only one.
Getting to Contract
Once you have selected a contractor, formalise the agreement. A simple domestic building contract (the JCT Minor Works form costs around £30 and is widely used) protects both parties. At minimum your written agreement should cover:
- Precise scope of works
- Contract sum and any provisional sums
- Payment schedule
- Start date and estimated completion
- Retention terms (typically 5%)
- Defects liability period
- How variations are handled and priced
A thorough brief at the start costs you a few hours. A disputed contract at the end costs far more.
