Small Kitchen Extension Cost
A small kitchen extension adds somewhere between 8 and 15 m²: enough to turn a kitchen you cook in into one you can sit in. It is the cheapest extension in total and the dearest per square metre, and knowing why helps you spend where it shows.
£20,000to£26,000
For 2.5 m deep and 4 m wide (10 m²). Building work at a standard to good finish, with VAT. A guide, not a quote.
Small kitchen extension prices
Building work only, including VAT, at 2026 national rates. Below 15 m² we price from the upper half of each range.
| Size | Floor area | Standard to good finish | High finish |
|---|---|---|---|
| 2 m by 4 m | 8 m²Room for a table for four | £16,000 to £21,000 | £22,500 to £24,000 |
| 2.5 m by 4 m | 10 m²A table, or a short peninsula | £20,000 to £26,000 | £28,000 to £30,000 |
| 3 m by 4 m | 12 m²An island becomes possible | £24,000 to £31,000 | £33,500 to £36,000 |
| 3 m by 5 m | 15 m²The small size on our price board | £27,000 to £39,000 | £39,000 to £45,000 |
Where these figures come from
- Planning Portal: planning permission for extensions
- GOV.UK: Approved Document L, conservation of fuel and power
- HMRC: Buildings and construction (VAT Notice 708), for the 20% rate on extensions
- GOV.UK: Fees for planning applications in England
- GOV.UK: Permitted development rights for householders, technical guidance
- GOV.UK: Building regulations approval
- GOV.UK: The Party Wall etc. Act 1996, explanatory booklet
Why small costs more per square metre
Some costs are the same whatever the size. The builder still sets up the site, hires a digger and a skip, breaks through the back wall, fits a steel beam, moves the drains and has building control out to inspect. The kitchen still needs its cooker circuit, its extractor duct and its plumbing. Spread over 30 m² those items disappear into the rate. Spread over 10 m² they are a large part of it.
So do not multiply a headline rate by a small area and expect a builder to agree. A 10 m² extension at the bottom of the standard range would be £18,000 with VAT; our table starts at £20,000, and that is the more realistic floor.
Extend, or rearrange what you have?
Before paying for foundations, look at the walls you already own. Knocking a kitchen through to the dining room behind it, or absorbing a utility room or an under-used hall cupboard, can add as much usable floor as a small extension for a fraction of the structure. It needs a beam and a building regulations application, but no roof, no foundations and usually no planning.
An extension earns its cost when the existing rooms are too narrow to combine, when the kitchen has no view of the garden, or when the family needs a table in the same room as the cooker and there is no wall left to remove.
Choices that keep the total down
Leave the sink, the boiler and the soil stack where they are, and build the new layout around them. Moving any of the three means new drainage or a new flue. Choose a flat roof with one good rooflight over a glazed roof. Fit French doors or a two-panel sliding door in place of a run of bifolds: on a 4 m wall the view is nearly the same.
Keep the extension to a simple rectangle, and keep it off the boundary by a metre if the plot allows. That avoids the eaves limit, usually avoids party wall surveyors, and gives the builder room to work from outside.
Permission and regulations still apply
Size earns no exemption. A small extension in England is normally permitted development, provided it stays within 3 m of the original rear wall on a terraced or semi-detached house (4 m on a detached one), but it needs building regulations approval in full: structure, insulation, ventilation, electrics and drainage. In Scotland a building warrant is required before work starts, and the permitted development limits are not the same as England's.
Fees do not shrink much either. Allow £600 to £1,200 for the engineer and £700 to £1,100 for building control even on the smallest job. A designer may charge less for a simple rectangle than the £1,000 to £2,500 typical of a larger scheme.
Small extension costs, answered
What is the cheapest way to extend a kitchen?
A plain rectangular rear extension with a flat roof, one rooflight, French doors and the sink left in place, built under permitted development so there is no planning fee. Reusing or reworking the existing kitchen units takes the largest single extra off the bill.
How much is a 3 m by 4 m kitchen extension?
That is 12 m². Allow about £24,000 to £31,000 for the building work with VAT at a standard to good finish, plus the kitchen and fees.
Is a small extension worth doing?
It depends on what it fixes. Two metres of depth that makes room for a table changes how a family uses the house. The same two metres added to a kitchen that is already workable is hard to justify against rearranging the rooms you have.
Other cost guides
- Kitchen extension costThe main guide, the price board and the calculator.
- Rear extension costThe straight extension across the back of the house, by depth and width.
- Side return extension costFilling the alley beside a Victorian or Edwardian kitchen.
- Kitchen diner extension costKnocking through and extending to make one family room.
Get a quote for a small kitchen extension
Your postcode, four quick questions about the job, then how to reach you. It takes about a minute.
This is a free introduction service, not a building firm. We find an extension builder who works in your area and tell you who they are. Your details go to them only when you say yes.
Thanks. We have your enquiry.
- We look for an extension builder who takes on kitchen extensions in your postcode area, then email or phone you with the firm's name.
- Nothing is passed on until you tell us to go ahead.
- The builder visits, measures up and prices the work. We will not send you marketing.