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The Builder's Brief UK
UK cost guide

Kitchen extension cost UK: what homeowners actually pay

A kitchen extension is two projects in one — the building work and the kitchen fit-out. Most budgets go wrong because the quote covers the first and only part of the second. Here is a plain-English breakdown of both, written by a working UK builder, so you can sanity-check your figures before you commit.

Quick answer

Quick answer
Budget roughly £60,000–£95,000 for a typical 20–25m² single storey kitchen extension with a mid-range fit-out, before VAT and professional fees. The shell is around £1,900–£3,500 per m²; a mid-range kitchen, plumbing, electrics and appliances usually add £15,000–£25,000 on top.
Best next step
Run your own numbers in the extension cost calculator, then check any quote you receive against the free builder quote checklist.
What to check
  • • Whether VAT is included or excluded
  • • Whether kitchen units and worktops are supplied or excluded
  • • Structural steel and the opening into the house
  • • Drainage moves and any soil pipe diversion
  • • Appliance supply and connection
  • • Flooring, decoration and making good
Important disclaimer
The Builder's Brief UK provides practical homeowner guidance only. It is not legal, financial, architectural, structural engineering, planning or building-control advice. Always use suitably qualified professionals where required.

Kitchen extension cost breakdown

Figures are typical UK ranges for a mid-range single storey kitchen extension, excluding VAT and professional fees. London and the South East usually run around 20% higher; parts of the North and Midlands run a little lower.

Typical UK kitchen extension cost items and ranges
ItemTypical costWhat moves the price
Extension shell (foundations, walls, roof, glazing)£1,900 – £3,500 per m²Mid-range single storey rear extension, before VAT and fit-out.
Structural steel and opening up to the house£2,500 – £8,000Depends on span, whether a wall is load bearing and engineer's design.
Kitchen units and worktops£6,000 – £20,000+Trade-supplied units at the lower end; bespoke or stone worktops at the top.
Plumbing and heating (sink, dishwasher, underfloor heating)£1,800 – £5,000Underfloor heating and moving a boiler or waste run push this up.
Electrics (sockets, lighting circuits, appliance supplies)£1,800 – £4,500Island sockets, feature lighting and extra circuits add cost.
Appliances£1,500 – £8,000Often bought by the homeowner and left out of the builder's quote.
Flooring, decoration and finishing£2,000 – £7,000Large-format tiles and engineered timber sit at the higher end.

On top of the build, allow 10–15% for professional and statutory fees (drawings, structural engineer, planning or permitted development checks, building control, party wall where relevant) and a 10–20% contingency.

Where kitchen extension budgets usually slip

  • The kitchen sits outside the quote

    Units, worktops and appliances are frequently a provisional sum or excluded entirely, so the headline price looks competitive until you add £15,000–£25,000.

  • Second-fix trades are under-priced

    Island sockets, extraction, underfloor heating and lighting circuits are easy to underestimate and awkward to add once the screed is down.

  • VAT is compared inconsistently

    One quote includes 20% VAT, another does not. Always normalise every quote to the same VAT basis before you compare.

  • Making good is forgotten

    Reinstating the existing room, plastering, skirting, decoration and levelling floor heights between old and new are real costs that often appear late.

Next steps for your kitchen extension

Estimate first, then check the quotes you receive line by line, then keep control of the budget once work starts.

Get the free checklist — free downloadCheck your quote before you accept — £9.99Take control of your project budget — £19.99

Prefer to run your own numbers first? Use the UK extension cost calculator or the AI extension cost estimator. For wider reading, see single storey extension costs in the UK and renovation costs homeowners forget.

Kitchen extension cost FAQs

How much does a kitchen extension cost in the UK?

For a typical 20–25m² single storey kitchen extension, most UK homeowners should budget around £60,000–£95,000 including a mid-range kitchen fit-out, before VAT and professional fees. A smaller side return with a modest kitchen can come in nearer £45,000, while a large open-plan kitchen-diner with bifolds, a lantern and a bespoke kitchen can pass £130,000.

Why is a kitchen extension more expensive than a plain extension?

The shell cost is similar, but a kitchen adds units, worktops, extra plumbing, additional electrical circuits, extraction, appliances and better flooring. Those trades and materials commonly add £15,000–£25,000 for a mid-range kitchen on top of the base build cost.

Is the kitchen itself usually included in a builder's quote?

Often not. Many builders price the shell plus installation and leave the kitchen units, worktops and appliances as a supply-by-homeowner item or a provisional sum. Always check whether supply, fitting, worktop templating and appliance connection are each priced.

How much should I allow for VAT on a kitchen extension?

Most VAT-registered builders add 20% VAT to labour and materials. On a £70,000 build that is another £14,000, so confirm early whether the figures you are comparing include or exclude VAT — mixing the two is one of the most common budgeting mistakes.

How long does a kitchen extension take?

A straightforward single storey kitchen extension usually takes around 10–16 weeks on site, plus design, planning or permitted development checks and building control beforehand. Allow extra time for kitchen lead times, which can be 6–10 weeks on their own.

What contingency should I allow?

Allow at least 10% on a modern property and 15–20% on an older house or a site with limited surveys. Drainage diversions, ground conditions and unexpected structural work are the usual causes of extra cost on kitchen extensions.

Do I need planning permission for a kitchen extension?

Many single storey rear extensions fall under permitted development, but limits on depth, height and materials apply, and they differ for terraced, semi-detached and detached homes. Always confirm with your local planning authority before you commit, and expect building control involvement either way.

How do I check whether a kitchen extension quote is complete?

Compare quotes line by line and look for the items that are usually missing: scaffolding, skips and waste, structural steel, drainage, making good to the existing house, decoration, flooring, kitchen fitting and appliance connection. Our free builder quote checklist walks through each of these in order.

The Builder's Brief UK provides practical homeowner guidance based on real trade experience. It is not legal, financial, architectural, structural engineering, planning or building-control advice, and is not a replacement for project-specific guidance from suitably qualified professionals.