Choosing a builder for an extension: beyond the cheapest quote
Compare builders on scope, sequencing, references, design responsibility and control approvals.
Applies to: UK homeowners; permissions and structural requirements depend on property and location.
Last checked: 16 October 2026
Key points
• Obtain drawings and a comparable schedule of works before comparing prices.
• Check who is responsible for design, structural calculations and building control.
• Request examples of extensions with similar access and site constraints.
Getting ready to arrange the work?
Search BuildPair for tradespeople who offer the services you need. Check profiles and discuss the details before agreeing to any work.
Why it matters
Two extension quotes can differ because one includes foundations, drainage and final finishes while the other covers only the shell. The apparent saving can disappear through exclusions.
Checklist before you start
• Ask for recent comparable projects and references.
• Confirm insurance, subcontractors, supervision and site security arrangements.
• List provisional sums and how unexpected ground conditions will be charged.
• Agree milestones, waste, temporary services, neighbour access and handover.
What to do next
Clarify how changes are priced and approved, and who will obtain building control sign-off. Keep a dated written record throughout.
Official sources
Use these official sources for the current detail that applies to your job, contract or location.
BuildPair provides general information and signposting, not legal, structural, electrical, gas or building-control approval. Requirements can change and the right answer depends on the work, contract, location and facts.
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