How Much Does a House Extension Builder Cost in the UK? (2026 City-by-City Guide)
The cost of hiring a house extension builder in the UK varies considerably depending on your location.
House Extension Builders in the UK should hold Building Regulations approval; FMB member recommended certification
(verified at Federation of Master Builders).
This guide lists 2026 house extension builder prices for all 200 UK cities in our database
— click any city for a full local pricing guide.
Regional price tip: London house extension builder costs typically run 40–50% above the national average.
Cities in the North East and Northern Ireland are often 15–25% below average.
Use the region jump-links below to find your area quickly.
📄 House Extension Builder — National Price Overview (2026)
UK Range (typical jobs)
£4,000 – £100,000
Typical Duration
8–20 weeks
Certification Required
Building Regulations approval; FMB member recommended
Cities Covered
200 UK cities
The UK national average is used as the baseline.
London typically costs 40–50% above the national average; Northern Ireland and
parts of the North East are 15–25% below.
Prices within each region can also vary by suburb and whether your job requires
emergency call-out rates.
What a House Extension Builder Job Typically Involves
A standard house extension builder quote usually covers:
Labour for groundworks, foundations, brickwork, roofing, and the full structural shell of the extension
Building Regulations applications, staged inspections, and a completion certificate on sign-off
Standard foundations, drainage connections, and a damp-proof course tied into the existing structure
First-fix and second-fix electrics and plumbing where included, plus plastering and insulation to current standards
Standard internal finishes, doors, and windows ready for decoration as set out in the agreed specification
An extension is a major structural build that must be designed to a structural engineer's calculations and constructed in compliance with the Building Regulations, with Building Control inspecting key stages from foundations upward and issuing a completion certificate at the end. Self-managing trades is possible for an experienced project manager, but the structural design, foundations, steelwork, and damp-proofing must be done correctly — defects here are hidden, expensive to remedy, and will be flagged on a future survey. Confirm at the outset whether the extension is permitted development or needs full planning permission, and whether a party wall award is required before any work begins.
UK house extension builder costs vary significantly by location. Typical job prices run £4,000 – £100,000. London tends to run 40–50% above the national average; cities in the North East and Northern Ireland are often 15–25% below. Click any city in the table above for a full local pricing breakdown.
Hourly rates for house extension builders depend on your location and the time of call-out. Standard daytime rates (Mon–Fri 8am–6pm) are the lowest; evening, weekend and emergency call-outs typically attract a 30–60% surcharge. Most house extension builders also charge a minimum call-out fee equivalent to 30–60 minutes of work.
Yes — House Extension Builder work legally requires Building Regulations approval; FMB member recommended certification in the UK. Verify credentials at Federation of Master Builders before hiring.
Always obtain at least three written, itemised quotes before committing to any house extension builder job. This lets you compare on price, qualifications and professionalism rather than defaulting to the lowest figure, which may indicate corner-cutting.
A proper house extension builder quote should state: the full scope of work, itemised labour and materials, whether VAT is included, expected start and completion dates, call-out or minimum visit fees, and any workmanship guarantee offered.
Yes — London house extension builder rates are typically 40–50% above the UK national average, driven by higher demand, travel costs and cost of living. The South East also runs 10–20% above average. Use the regional tables above to find your city's rates.
Use the official Federation of Master Builders checker to verify registration in seconds. Ask the tradesperson to produce qualification certificates, public liability insurance documents, and any relevant accreditation before work begins. A trustworthy professional will have these documents readily available.
A deposit of 10–20% is normal practice for larger house extension builder jobs. Never pay more than 25% upfront, and always pay by card or bank transfer rather than cash so you have a clear payment record. Avoid any tradesperson who demands full payment before starting.
Warning signs include: demands for a large cash deposit before any work starts, inability to produce insurance or qualification proof, refusal to provide a written quote, significantly undercutting all other estimates, and pressuring you to decide immediately. A reputable house extension builder will never rush you.
Use vetted platforms such as Checkatrade, Rated People or TrustMark to find reviewed house extension builders in your area. Personal recommendations from neighbours or friends remain the most reliable method. Always verify public liability insurance of at least £1 million before agreeing to any work.
Price disclaimer: Prices above are 2026 estimates based on regional
trade cost-index data. Actual quotes will vary by contractor experience, job complexity,
materials, and market conditions. Always request at least three written quotes before
committing to any work.
ServicePriceHub.uk is an independent price reference guide and is not affiliated with
any tradesperson or trade body.
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