Kitchen extension cost
Open-plan kitchen extension costs for 2025 — rear and side return. In the UK, expect to pay between £30,000 and £120,000, with the typical project around £55,000 (average kitchen extension + new kitchen (3 bed)). Regional variation, specification tier and site access conditions all shift the final quote.
Homeowners researching this typically also price up new kitchen cost and bifold doors cost. For wider context, browse our bathroom pricing, boiler & heating costs and trades day rates.
Cost table
| Item | Typical range (GBP) |
|---|---|
Small rear extension + kitchen (4m x 4m) — 16m² extension, mid-range kitchen | £30,000–£55,000 |
Medium extension + kitchen (4m x 6m) — 24m², open-plan, bifold doors | £50,000–£85,000 |
Side return + rear extension — L-shaped, full open-plan transformation | £55,000–£100,000 |
Premium open-plan (architect designed) — High spec, lantern, feature kitchen | £75,000–£120,000 |
Labour costs
Labour typically accounts for 50% of the total project cost in the UK.
| Item | Typical range (GBP) |
|---|---|
All trades (builder, elec, plumber) | £25,000–£55,000 |
Architect fees | £2,500–£6,000 |
Structural engineer | £800–£2,000 |
Project management | £2,000–£5,000 |
Materials costs
Materials and fittings make up the remainder of the budget, with specification tier driving most of the variation.
| Item | Typical range (GBP) |
|---|---|
Extension (structure) | £15,000–£40,000 |
New kitchen (mid-range) | £8,000–£20,000 |
Bifold doors (3.6m) | £3,500–£7,000 |
Roof lantern | £2,500–£8,000 |
Underfloor heating | £2,000–£5,000 |
Factors affecting cost in the UK
- ·Region — London and the South East run 15–30% above national averages.
- ·Specification tier — premium materials and finishes can double the base cost.
- ·Access and site conditions — flats, restricted parking and listed buildings add time.
- ·Scope changes mid-project — late design decisions are the biggest cost overrun driver.
- ·Trade availability — quotes rise 10–20% in peak spring and summer months.
Ways to reduce cost
- ·Stay within permitted development limits (under 3 m for terrace, 4 m for detached) to skip planning.
- ·Choose a single-storey rear rather than wraparound or side return for lowest £/m².
- ·Bundle kitchen + extension into one contract via a design-and-build company.
- ·Specify mid-range glazing rather than minimal-frame structural glass.
- ·Use standard brick or render rather than zinc or timber cladding.
Frequently asked questions
- What is the average cost of a kitchen extension in the UK?
- A kitchen extension typically costs £30,000–£85,000 depending on size and specification, including the extension structure and a new kitchen. London adds 25–35% to these figures.
- Does a kitchen extension need planning permission?
- Many kitchen extensions fall under permitted development if single-storey and extending no more than 3m (semi/terraced) or 4m (detached). The Prior Approval Neighbour Consultation Scheme allows up to 6m/8m. Always verify before starting.
- What is a side return extension?
- In Victorian and Edwardian terraced and semi-detached homes, the side return is the narrow alley alongside the kitchen. Infilling this space (typically 1–1.5m wide) with an extension creates a significantly wider kitchen-diner and is one of the most popular extensions in urban UK.
Sources & how we estimate
Prices are typical UK ranges compiled by ModernExpert.AI from published trade rates and supplier price lists, and are estimates — always get at least three written quotes. Rules on permissions, safety and certification come from the official sources below. Last reviewed 19 October 2026.
- Approved Document P — Electrical safety in dwellings
- Gas Safe Register — Find an engineer
- GOV.UK — Building regulations approval
- Planning Portal — Do you need permission?
- ONS — Construction output price indices
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