Cost of a Kitchen Extension in the UK (2025)
A kitchen extension costs £35,000–£85,000 depending on size and specification. Adding bifold doors, skylights, and an open-plan layout are the most popular choices.
What does a kitchen extension cost include?
A kitchen extension quote should cover groundworks and foundations, external walls (brick or blockwork), roof (flat roof with lantern, pitched, or glass roof), rear wall demolition and steel beam installation, windows and doors (including bifold or sliding doors), external insulation, internal plastering, first and second fix electrics and plumbing, and underfloor heating if specified. The kitchen itself is usually a separate cost.
The most popular kitchen extension features
Bifold or sliding doors to the garden are now standard in most kitchen extensions — budget £3,000–£8,000 for quality thermally broken aluminium doors. A roof lantern over a flat roof extension brings in natural light (£2,000–£6,000 installed). Underfloor heating (£3,000–£6,000 for the extension area) is popular as there are no radiators to interrupt the open-plan layout.
Cost Breakdown
All prices are indicative UK averages for 2025. Actual costs vary by location, specification, and contractor. London and South East rates are typically 20–35% higher.
| Item | Low | High |
|---|---|---|
| Single storey kitchen extension (3m x 3m) | £28,000 | £45,000 |
| Single storey kitchen extension (4m x 5m) | £42,000 | £70,000 |
| Side return extension (typical terrace) | £30,000 | £55,000 |
| Wrap-around extension | £55,000 | £95,000 |
| Bifold doors (4m opening) | £3,000 | £7,000 |
| Roof lantern (3m x 1.5m) | £2,000 | £5,000 |
What Affects the Cost?
- ✓Size — metres squared is the primary cost driver
- ✓Roof type — flat roof is cheaper, pitched roof or glass more expensive
- ✓Doors — bifold and sliding doors add significant cost
- ✓Underfloor heating specification
- ✓Structural complexity — loading conditions, existing foundations
- ✓London and South East — 30–40% premium vs national average
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Post a Job — It's FreeFrequently Asked Questions
Does a kitchen extension need planning permission?
Many kitchen extensions qualify as Permitted Development, particularly single-storey rear extensions within certain size limits. However, if you are in a conservation area, an AONB, or want an extension that exceeds PD limits, a planning application is needed. Expect 8–13 weeks for a decision.
Should I get a new kitchen at the same time as the extension?
Yes — this is almost always the right approach. Installing a new kitchen immediately after the extension is complete avoids disruption later and allows the kitchen design to be planned specifically for the new open-plan space.
How much value does a kitchen extension add?
A well-executed kitchen extension in the right area can add 5–15% to property value. In high-value areas, the return can be greater. Open-plan kitchen-diners are consistently the most in-demand feature for house buyers.
Can I use my kitchen during the extension build?
For the first few weeks (groundworks and external walls), yes. When the rear wall is demolished, you will lose the kitchen for 2–4 weeks. Plan alternative cooking arrangements for this period. Your builder should minimise this disruption.