A kitchen extension is two jobs priced together: building the extension, and fitting out the kitchen inside it. The Federation of Master Builders puts a single-storey kitchen extension from around £1,700 per square metre, and the average single-storey extension at £1,800 to £3,000 per square metre. If you already have the floor area, knocking through an internal wall can cost a fraction of that.
The build: cost per square metre
The FMB gives £1,800 to £3,000 per square metre as the average for a single-storey extension, with London and the South East costing 30 to 50% more in some cases. The HomeOwners Alliance puts a standard 20 square metre single-storey extension at around £48,000 plus VAT, within a typical range of £40,000 to £56,000. That's the shell — the new kitchen goes on top. Ground conditions, the roof, glazing, services and structural steel can all move the figure.
Knocking through instead of extending
If the floor area is already there, removing an internal wall to combine the kitchen with another room is often simpler and cheaper than building out. The FMB cites one architectural firm in the South and East of England at £1,200 to £5,000 to remove an internal wall, depending on whether it's load-bearing; a load-bearing wall needs a steel beam, which costs extra. Planning permission isn't usually needed for this, but a shared wall may bring the Party Wall Act into play.
Fitting the kitchen
You can use an independent fitter, often organised by your builder, or the kitchen retailer's own installation service. The FMB quotes a London member at around £300 a day for a kitchen fitter, and notes that labour often ends up at about 20 to 30% of the final kitchen cost. Retailer-managed installation for a standard kitchen is typically £3,000 to £4,000, scaling with size and complexity, and usually excludes plumbing and electrical cabling — check exactly what's included.
Services, finishes and appliances
The FMB's figures for the smaller items: moving a boiler from around £200 for a straightforward relocation, which must be done by a Gas Safe registered engineer; tiling a splashback from around £30 per square metre; and floor fitting from under £20 per square metre for vinyl, £50 for tiles and £60 for laminate. Fitting appliances adds up too — from about £30 to connect a freestanding washing machine to around £115 for an integrated one, and £100 to £125 for an oven.
What gets left out of quotes
The FMB lists the extras that catch people out: scaffolding, skip hire, setting up a temporary kitchen while the work is done, and decorating at the end. Drains may need moving or building over. If you need planning permission, the application fee in England is £528. Building control charges a fee as well, and VAT at 20% applies to most building work. Ask every builder which of these their quote covers.
How to budget sensibly
Plan the layout and storage before you get quotes, since changing them later is expensive. Get three detailed written quotes and compare them line by line, and be wary of one that's much cheaper than the rest: the FMB warns that costs often rise as the job goes on. Keep a contingency of around 10% for the unexpected.
Frequently Asked Questions
Do I need planning permission for a kitchen extension?
Often not. Many single-storey rear extensions fall under permitted development, provided they stay within size and design limits. Our guide to planning permission for extensions sets out the limits.
Is it cheaper to knock through than to extend?
Usually, if you already have enough floor area. Removing an internal wall typically costs from about £1,200 to £5,000, depending on whether it's load-bearing, against roughly £1,700 per square metre or more to build out.
How much does it cost to have a kitchen fitted?
Retailer-managed installation for a standard kitchen is typically £3,000 to £4,000, usually excluding plumbing and electrics. An independent fitter charges around £300 a day, according to the FMB.
Where this information comes from
- Federation of Master Builders — Kitchen extension cost 2026
- Federation of Master Builders — Single-storey extension costs
- HomeOwners Alliance — House extension costs
General information only, not legal or financial advice. Last checked 2026-10-09.
