Budget
£39,500
- Basic single-storey footprint increase with standard glazing
- Straightforward finishes
House Extension Costs in London
Estimates derived from UK trade benchmark data and regional labour indices, updated May 2026. Methodology →
House Extension in London typically lands above the UK-wide average for the same spec. We start from our national guide ranges and reflect the labour and logistics pressure you usually see in the capital.
In London, labour and logistics costs are typically highest across UK regions. For the full UK-wide baseline, compare with House Extension Cost UK.
London extensions are planning projects first and construction projects second. Permitted-development rights are curtailed across much of inner London by Article 4 directions and conservation areas, so schemes that would be automatic elsewhere need full applications; party-wall agreements are near-universal because almost every extension touches a shared wall in terraced stock. Budget for both the surveyor fees and the months, not weeks, of lead time.
On site, the cost drivers are access and ground: rear extensions on Victorian terraces are frequently hand-dig jobs with skip logistics per load, London clay demands deeper foundations than most UK soils, and basement or side-return schemes bring structural engineering that dominates the budget. The London premium therefore compounds — dearer labour on more labour-intensive designs.
Two ways to take action on extension costs
Pick the path that fits where you are — running early numbers, or pressure-testing a quote you've already got.
Typical London house extension budgets
Three planning tiers for house extension in London, with scope and a representative figure for each. Run your own numbers in the calculator for a tailored range.
Mid-rangeMost common
£73,000
- Kitchen-diner extension with rooflights
- Good insulation
- Moderate internal reconfiguration
Premium
£207,500
- Complex steelwork
- Premium glazing
- Bespoke joinery
Typical regional cost ranges
| Item | Cost Range |
|---|---|
| Single-storey rear (small, 15 m²) | £24,500 – £49,000 |
| Single-storey rear (medium, 25 m²) | £42,500 – £79,500 |
| Single-storey build (per m²) | £1,450 – £3,400 |
| Double-storey (25 m² total) | £55,000 – £85,500 |
| Double-storey (40 m² total) | £73,000 – £116,000 |
Indicative range: £1,450–£3,650 per m².
At the mid-range, house extension in London benchmarks around £61,000 — around 22% above the UK average. That is roughly 30% above North East England (£47,000), the UK's most affordable region for the same spec. Next door, South East England comes in around £56,000 and East of England comes in around £53,000.
How house extension costs vary across London
London is not one price. Across the postcode areas we track, Central London quotes typically run 23% higher than Romford for the same spec — these are the benchmarks by area:
| Area | Postcodes | vs UK average | Typical mid-range | Budget–premium span |
|---|---|---|---|---|
| Central London | WC | +40% | £70,000 | £28,000–£168,000 |
| City of London | EC | +38% | £69,000 | £27,500–£165,500 |
| South West London | SW | +38% | £69,000 | £27,500–£165,500 |
| West London | W | +38% | £69,000 | £27,500–£165,500 |
| East London | E | +32% | £66,000 | £26,500–£158,500 |
| North West London | NW | +32% | £66,000 | £26,500–£158,500 |
| Uxbridge | UB | +18% | £59,000 | £23,500–£141,500 |
| Bromley | BR | +16% | £58,000 | £23,000–£139,000 |
| Croydon | CR | +16% | £58,000 | £23,000–£139,000 |
| Enfield | EN | +16% | £58,000 | £23,000–£139,000 |
| Sutton | SM | +16% | £58,000 | £23,000–£139,000 |
| Romford | RM | +14% | £57,000 | £23,000–£137,000 |
Plus 6 more postcode areas between these ends of the range. Run the calculator with your postcode for a range tuned to your area.
Mini extension cost calculator
Three quick inputs and we'll email you an indicative range. Run the full calculator for a postcode-adjusted estimate.
Checking a London house extension quote?
What a fair house extension quote should itemise doesn't change by region — only the prices do. The full checklist, red flags and scripts live in our UK guide, benchmarked against the London figures above:
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Other renovation costs in London
All London renovation costsFrequently asked questions
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