Kitchen extension cost UK
A kitchen extension costs more than a plain family-room shell because plumbing, gas, electrics, extraction and often a boiler move all travel with the room. Checkatrade’s 2026 kitchen extension guide puts a medium kitchen extension around £30,000 on average, and notes that kitchen-specific work can add £15,000–£35,000 compared with a basic room extension of similar size.
Always ask what a quote includes: foundations and structure only, first-fix plaster, or a complete kitchen with appliances. VAT (where charged) and professional fees are easy to miss in headline per m² rates.
Kitchen extension cost per m²
Per m² rates help you compare quotes of different sizes. From Checkatrade’s kitchen-diner and kitchen guides (as of 2026):
| Item | Typical range | Notes (as of 2026) |
|---|---|---|
| Kitchen diner extension | £1,500–£2,000 / m² | Excluding VAT; average ~£1,750 / m² |
| Single-storey kitchen extension | £1,650–£2,300 / m² | Excluding professional fees |
| Professional fees | 10–15% of project | Architect / designer / engineer |
| Basic kitchen units (small) | £5,000–£6,000 | Supply; higher specs cost more |
| Side return (small) | £30,000–£45,000 | Before a high-spec kitchen |
London and the South East often sit at the top of (or above) national ranges. House-extension guides that quote £1,800–£3,000 per m² for general extensions still flag kitchens as a premium fit-out on top.
Single-storey kitchen extension cost
Single storey kitchen extension cost depends on shape as much as size:
- Full-width rear. Popular for open-plan kitchen diners; watch permitted development depth (3 m / 4 m, or 6 m / 8 m with prior approval in England).
- Side return. Fills the alley beside a rear addition on Victorian terraces; lots of glass and waterproofing detail for relatively few m².
- Wrap-around. Side plus rear in one L-shape; usually needs careful planning analysis and more steel.
- Rear with roof lantern. Daylight helps value; lanterns and sliding doors are large ticket items.
For a 20 m² kitchen diner, Checkatrade’s breakdown example lands around £30,000–£40,000 excluding professional fees, with structure roughly £15,000–£20,000, a basic kitchen £5,000–£6,000, electrics £5,000–£6,000, flooring £1,500–£2,000 and decorating £4,000–£5,000 in their illustrative split.
Layouts that add value
Buyers pay for a clear cooking, dining and circulation layout — not for the maximum number of roof lights. Layouts that usually help resale:
- Sight line to the garden. Island or peninsula that does not block the rear glazing.
- Utility separation. Noisy appliances and muddy boots kept out of the show kitchen.
- Enough wall for tall storage. Reduces expensive bespoke furniture later.
- Realistic boiler and cylinder space. Moving a boiler mid-project is a classic cost spike — budget it early (see our new boiler cost guide).
Open-plan does not automatically add 10% to value on every street. In smaller terraces, a well-planned side return can outperform a deep rear box that steals the garden.
Worked example: 20 m² kitchen diner
Worked example
You want a 20 m² single-storey rear kitchen diner outside London. Using Checkatrade’s kitchen-diner average of £1,750 per m² excluding VAT: 20 × £1,750 = £35,000 for the build band they associate with that size (£30,000–£40,000). Add 12.5% professional fees → about £4,375. If your kitchen upgrade is mid-range rather than the £5,500 basic allowance already sketched in some breakdowns, keep a separate £10,000–£20,000 line for units, worktops and appliances.
Answer: Plan on roughly £35,000 + fees for a 20 m² kitchen-diner shell/fit band, then price the kitchen specification separately — refine with the Home Extension Calculator and local quotes.
Ways to keep costs down
- Fix the planning route early. Redesigning after a refusal wastes fees. Check permitted development depth before you fall in love with a 7 m rear projection on a semi.
- Reuse the boiler position if safe and compliant. Relocations need Gas Safe work and new flues.
- Standardise openings. One wide sliding door often costs less than a wall of bespoke pivots.
- Separate shell and kitchen contracts clearly. Know who supplies worktops, appliances and tiling.
- Get three comparable quotes. Same drawings, same exclusions, same VAT treatment.
Size the shell with the Home Extension Calculator, then read the permitted development extension rules before you submit drawings.
Regional differences and VAT
National per m² bands hide large regional spreads. London single-storey rates in secondary guides often sit hundreds of pounds per m² above UK averages, and scarce skip access or restricted hours add labour. Commuter-belt towns can track London pricing even when headline “UK average” tables look softer.
Ask every tenderer whether prices are including or excluding VAT. Checkatrade’s kitchen-diner per m² band is explicitly excluding VAT; a 20% swing changes a £35,000 shell into £42,000 on the invoice. Domestic work for homeowners usually attracts VAT unless a specific relief applies — do not assume zero-rated construction.
Professional fees of 10–15% cover measured surveys, planning or prior-approval drawings, structural calculations and sometimes contract administration. Cutting fees by sketching on graph paper rarely survives Building Control or a steel schedule.
What to put in the brief
- Target floor area and ceiling height. State whether you need 2.4 m clear height or will accept a lower flat roof.
- Appliance and boiling-water list. Induction hobs, boiling taps and dual dishwashers change electrics and water services.
- Boiler and cylinder decision. Stay, move, or replace — priced as options, not surprises.
- Floor finish and underfloor heating. Screed depth and door thresholds must be designed, not improvised.
- External works. Drainage runs, patio make-good and fence resets are easy to omit from “extension only” quotes.
Value is usually won in daylight, storage and a garden connection that still leaves outdoor space usable. A deep rear box that leaves a 2 metre strip of patio can hurt saleability even if the kitchen itself photographs well. Side returns that unlock width without stealing garden depth are popular on terraces for that reason — just remember their £30,000–£45,000 band still needs a kitchen budget on top.
When quotes arrive, normalise them to the same m², the same exclusions, and the same VAT treatment, then decide. Use the Home Extension Calculator for a sanity check on area-driven cost before you negotiate finishes.
Kitchen spec versus shell
Split the project mentally into shell (foundations, walls, roof, windows, plaster) and kitchen (units, worktops, appliances, splashbacks). Shell cost tracks m² and structural complexity; kitchen cost tracks specification. Mixing them in one vague number makes it impossible to value-engineer.
A basic kitchen allowance of around £5,000–£6,000 in some Checkatrade breakdowns is not a handleless quartz island with boiling tap. Mid-range fitted kitchens commonly sit well above that before appliances. If resale is the goal, spend first on daylight, waterproofing and a durable floor; those are hard to retrofit. Fancy tapware is easy to change later.
Steel beams that open the rear wall into the new space are another frequent upgrade. Budget structural engineer fees and temporary propping in the programme, and accept that Opening-up day is when hidden defects (rotten lintels, uninsulated cavities) appear. A 10% contingency on kitchen extensions is prudent precisely because services and structure reveal themselves late.
Finally, sequence: weatherproof shell, first-fix electrics and plumbing, then kitchen install. Compressing those stages to “save time” is how worktops arrive before plaster is dry.
Frequently Asked Questions
How much does a kitchen extension cost in the UK?
Checkatrade cites an average around £30,000 for a medium kitchen extension in its 2026 kitchen guides, with kitchen-diner work often £1,500–£2,000 per m² excluding VAT. Specialist kitchen services can add £15,000–£35,000 on top of a basic room extension.
What is the kitchen extension cost per m²?
As of 2026 Checkatrade guides: about £1,500–£2,000 per m² excluding VAT for a kitchen diner (average £1,750), and about £1,650–£2,300 per m² excluding professional fees for a single-storey kitchen extension. London rates are higher.
How much is a 20 m² kitchen diner extension?
Checkatrade’s kitchen-diner guide lists roughly £30,000–£40,000 for a 20 m² build excluding professional fees, before a higher-spec kitchen. Add 10–15% for design fees and VAT where applicable.
Does a side return cost less than a full-width rear extension?
Side returns are smaller in m² but still need foundations, waterproofing, steels and glazing. Checkatrade notes small side-return extensions often land around £30,000–£45,000 before a full new kitchen.
Do I need planning permission for a kitchen extension?
Many single-storey rear kitchen extensions on houses in England fall under permitted development if they stay within depth and height limits. Larger depths need prior approval or full planning. Building Regulations always apply.
Sources
- Checkatrade — Kitchen diner extension costs — £1,500–£2,000 per m² ex VAT; 20 m² £30k–£40k; single-storey £1,650–£2,300 per m².
- Checkatrade — Kitchen extension cost 2026 — Average ~£30,000 medium extension; +£15k–£35k for kitchen complexity vs a basic room.
- Checkatrade — House extension cost — Kitchen add-on £15k–£35k vs standard room extension (updated June 2026 in guide).
- Planning Portal — Extensions — Planning vs permitted development for house extensions in England.
When you are ready to estimate materials or cost for your project, open the Home Extension Calculator and enter your measurements.