Average Cost of a New Kitchen Extension in 2026 (UK)
A kitchen extension is two projects bought as one: the shell, and the kitchen that goes inside it. Homeowners consistently budget for the first and are surprised by the second. In 2026 the average UK kitchen extension costs £42,000–£85,000 fully fitted, and understanding the split between build cost and fit-out is what separates a realistic budget from an overrun.
What does a kitchen extension cost on average in 2026?
The average UK kitchen extension costs £42,000–£85,000 fully fitted in 2026. A modest 15 m² single-storey rear extension with a mid-range kitchen typically lands at £42,000–£58,000. A 25 m² open-plan kitchen-diner with bi-folds and a premium kitchen runs £65,000–£95,000. Wraparound and side-return schemes in London regularly exceed £110,000.
The useful rule of thumb: the shell costs roughly £2,200–£3,200 per m², and the kitchen fit-out is a separate £8,000–£35,000 on top. Budgets fail when the second number is treated as an afterthought.
Kitchen extension cost by size and specification (UK 2026)
| Extension type | Typical size | Shell cost | Kitchen fit-out | Total fitted |
|---|---|---|---|---|
| Small rear extension | 12–15 m² | £30,000–£45,000 | £9,000–£18,000 | £42,000–£58,000 |
| Standard kitchen-diner | 18–22 m² | £42,000–£62,000 | £12,000–£25,000 | £55,000–£80,000 |
| Large open-plan extension | 25–30 m² | £58,000–£85,000 | £15,000–£35,000 | £75,000–£110,000 |
| Side-return (terrace) | 10–16 m² | £38,000–£60,000 | £10,000–£25,000 | £50,000–£82,000 |
| Wraparound | 28–40 m² | £70,000–£105,000 | £15,000–£35,000 | £88,000–£135,000 |
London and the South East run 25–40% above these figures; the North East, Yorkshire, Wales and Northern Ireland typically sit 15–20% below. See the full kitchen extension cost guide for a detailed line-item breakdown.
The shell-versus-fit-out split most budgets miss
Builders quote the shell. Kitchen showrooms quote the kitchen. Neither quote is wrong, but neither is the whole project — and homeowners routinely add the two headline figures while omitting the work that sits between them.
| Cost element | Typical share of total | Commonly missed? |
|---|---|---|
| Groundworks & foundations | 12–18% | No |
| Superstructure, roof & weathertight shell | 28–35% | No |
| Glazing (bi-folds, rooflights, sliders) | 8–15% | Frequently understated |
| Kitchen units, worktops & appliances | 18–30% | No |
| M&E: electrics, plumbing, heating, ventilation | 8–12% | Yes |
| Plastering, flooring & decoration | 6–10% | Yes |
| Professional fees & Building Control | 5–10% | Yes |
| Party wall & structural engineering | 1–4% | Yes |
The four elements marked "yes" typically account for 20–30% of the true total and are the usual source of a £10,000–£20,000 shortfall. Add a 10–15% contingency on top — drainage diversions, unexpected foundation depth and asbestos in older properties are common discoveries once the ground is opened.
Does a kitchen extension pay for itself?
Rarely in full, and homeowners who expect it to are usually disappointed. A well-designed kitchen extension typically returns 60–80% of its cost in added value in most of the UK, with the strongest returns in high-value areas where the extra floor area is scarce and the weakest where local ceiling prices cap what any single property can achieve.
The decisive factor is the local ceiling price. Spending £70,000 on a property already close to the top of its street's price range reliably destroys value. The same spend on an under-improved house in a strong area can return most or occasionally all of the outlay. Check sold prices for comparable extended properties within a few streets before committing — and read our analysis of how much a kitchen extension adds to value.
Where a kitchen extension consistently justifies itself is on use rather than resale: it is bought for the decade of daily living it delivers, not the exit price.
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Kitchen Extension Cost Questions (UK 2026)
Where these figures come from
- Planning Portal — house extensions
- gov.uk — Approved Document A (Structure)
- gov.uk — Party Wall Act
- RICS — Royal Institution of Chartered Surveyors
- FMB — Federation of Master Builders
- Companies House — verifying a contractor
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