Single-storey extension cost UK 2026
Most UK single-storey extensions cost £1,500–£3,000 per square metre fitted. A typical 20m² rear extension lands £30,000–£60,000 in 2026 prices. Below: full breakdown by size, spec, and region, with methodology.
Cost guide ranges by size
| Size | Standard finish | Premium finish | Luxury finish |
|---|---|---|---|
| 10m² (small lean-to) | £15,000–£22,000 | £22,000–£30,000 | £30,000–£40,000 |
| 15m² (galley/utility) | £22,000–£35,000 | £32,000–£45,000 | £42,000–£60,000 |
| 20m² (kitchen extension) | £30,000–£48,000 | £42,000–£60,000 | £55,000–£80,000 |
| 30m² (kitchen+dining) | £45,000–£70,000 | £60,000–£90,000 | £80,000–£120,000 |
| 40m+ (large open-plan) | £60,000–£100,000 | £85,000–£135,000 | £120,000–£180,000+ |
What's included in these ranges
- Foundations (concrete trench-fill or strip)
- External walls (cavity construction with brick or render finish)
- Flat or pitched roof with insulation, tiles or membrane
- Standard double-glazed windows and rear doors
- First fix electrics and plumbing for one room
- Plastering, decoration, basic flooring
- Internal door (if separating from existing space)
- Building regs application and structural calcs
What's NOT included (typical add-ons)
- Kitchen units and worktops if it's a kitchen extension (£8,000–£25,000+)
- Bi-fold or sliding doors (£3,000–£10,000+ vs standard French doors)
- Underfloor heating (£60–£100/m²)
- Skylights or roof lanterns (£800–£3,500 each)
- Removing structural walls inside (£1,500–£5,000+ depending on RSJ specification)
- Exterior landscaping after build (£1,000–£5,000+)
- Planning application if outside permitted development (£200–£500)
Regional variation
- London & South East — typically 25–40% above the headline rate above. Premium of £2,500–£3,500/m² is normal.
- Major cities (Manchester, Bristol, Edinburgh) — broadly in line with headline rates.
- North, Wales, Scotland (rural) — typically at the lower end. £1,500–£2,200/m² achievable.
What drives the price
Per-m² figures vary widely because the headline number bundles every variable: ground conditions, design complexity, glazing percentage, roof type, finish quality, kitchen spec, and the contractor's overhead. The biggest single multiplier is finish quality — a "standard" 20m² extension can be £30,000 or £80,000 depending on whether it's basic-spec or designer-finished.
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How we estimated these ranges
This is a guide only. The ranges below are intended for early budgeting and trade benchmarking. They are not a substitute for a site visit or an itemised quote from a qualified tradesperson. Always get a site-specific quote before agreeing work.
What's included in these ranges: typical labour costs, common materials at standard specification, and routine preparation or installation work for a standard project of this type.
What's excluded: unusual access (multi-storey, restricted parking), unforeseen structural issues, specialist design or architect fees, planning and building control application fees, premium or high-end finishes, emergency or out-of-hours work, and regional extremes.
Regional note: London, the South East and remote rural areas can vary significantly from the UK averages shown. London labour rates in particular can run 30–50% higher than national averages on the same scope.
Sources and checks used: publicly available UK trade supplier pricing (2025–2026), common day-rate and labour-duration assumptions used in trade quoting, internal example quote structures from TailoredQuote platform data, and where relevant cross-referenced regional contractor surveys and BCIS-style construction cost data.
Last reviewed: May 2026 by TailoredQuote. Prices in this guide will be reviewed and updated periodically.
Frequently asked questions
£1,500–£3,000 fitted, depending on spec and region.
Single-storey rear extension on flat ground with a flat roof.
Often falls within permitted development. Check size limits.
8–14 weeks typically.
Related cost guides
Last reviewed: May 2026
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