ToolsProfessional Tool
Extension & Renovation Cost Estimator
A region-adjusted UK build cost in seconds, broken down by work stage, with adjustable fees, contingency and VAT, plus an indicative on-site programme.
2026 UK build rates · region-adjusted
5m²200m²
Good quality mid-range spec
Advanced settings
Architect, engineer, building control, surveys
10–15% typical; more for older buildings
Some conversions and long-empty properties qualify for reduced VAT — check with HMRC.
Estimated total project cost
£62,112 — £76,512
UK average (0% vs UK avg)£2,100–£2,700 / m² ~13 weeks on site
What's included
Build cost (mid-range)£48,000
Professional fees (12%)£5,760
Contingency (10%)£4,800
VAT (20%)£10,752
Build cost by work stage
Preliminaries, access & site setup£3,840 (8%)
Groundworks & foundations£6,720 (14%)
Superstructure (walls, floors, steel)£11,520 (24%)
Roof & external envelope£6,720 (14%)
First fix (electrics, plumbing, carpentry)£6,720 (14%)
Second fix & finishes£9,120 (19%)
External works & making good£3,360 (7%)
Ballpark guide only, based on typical 2026 UK build rates. Actual costs vary with site conditions, access, ground works and market conditions. For accurate drawings and costed designs, request a free quote.
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