Home & Construction⏱ 6 min read
How to Budget a Home Renovation: A Cost-per-Square-Metre Guide
Renovation costs are notoriously unpredictable — but not unknowable. Here is a room-by-room cost guide, the formula for contingency budgeting, and the hidden costs that wreck most budgets.
Home renovation costs depend on specification, location, and the state of the existing structure. The cost-per-square-metre benchmarks below are for mid-range UK work (2024 prices) — premium finishes or structural complications will push these up significantly.
Room-by-Room Cost Benchmarks (UK, 2024)
Renovation TypeBudgetMid-rangePremium
Kitchen (per m2 floor)£800-1,200£1,500-2,500£3,500+
Bathroom (per m2)£600-900£1,000-1,800£2,500+
Loft conversion (per m2)£1,200-1,500£1,500-2,000£2,500+
Extension (per m2 GIA)£1,500-2,000£2,000-3,000£3,500+
Rewire (per m2)£25-35£35-50£50-70
Replumb (per m2)£30-45£45-65£65-90
Budgeting Formula with Contingency
Base cost estimate = Sum of all room/scope estimates
Contingency allowance:
New build or well-understood scope: 10-15%
Renovation of known-condition property: 15-20%
Victorian / Edwardian property (unknown structure): 20-30%
Listed building or complex works: 30-50%
Total project budget = Base estimate x (1 + Contingency %)
Example: kitchen renovation, 12 m2, mid-range spec:
Base estimate: 12 x £2,000 = £24,000
Contingency (20%): £4,800
Total budget: £28,800
Rule: never present a renovation budget without contingency.
The contingency is not waste — it is the most realistic part of the estimate.
The Hidden Costs That Wreck Budgets
Costs frequently excluded from initial quotes:
Planning permission (if required): £206-£462 application fee
Architect / designer fees: 5-15% of build cost
Structural engineer report: £400-£800
Party wall surveyor (shared walls): £700-£1,500 per owner
Building control fees: £400-£1,500 depending on works
Temporary accommodation: £0-£3,000+ per month
Skip hire: £200-£400 per skip
Site clearance before work starts: £300-£800
VAT: most building work is standard-rated at 20%
(New builds and some conversions are zero-rated — check with builder)
Adding VAT example:
Quote of £20,000 + VAT = £24,000 actual cost
Always ask: "Is your quote inclusive or exclusive of VAT?"
Value Added by Renovation Type
Rough UK average added value (varies enormously by location):
Kitchen renovation: recoups 50-75% of cost in sale price
Bathroom renovation: recoups 50-65% of cost
Loft conversion (adds bedroom): recoups 75-100% of cost
Extension (adds m2): recoups 70-90% of cost
These are averages — in strong markets, returns can exceed cost.
In weak markets or with poor specification, returns can be negative.
Return on investment formula:
ROI = (Sale price increase - Renovation cost) / Renovation cost x 100
Loft conversion costs £35,000, adds £45,000 to value:
ROI = (45,000 - 35,000) / 35,000 x 100 = 28.6%