Kitchen Extension Cost UK (2026): Prices, Per m² & Examples

How much does a kitchen extension cost in 2026?

A kitchen extension is really two projects bolted together: the building work (foundations, walls, roof, glazing, plastering, electrics) and the kitchen (units, worktops, appliances and fitting). Many online figures mix the two, which is why you will see headline numbers anywhere from £20,000 to £150,000. Pricing them separately gives a far more reliable budget.

For the build, most UK cost guides land in a similar band. Homebuilding & Renovating puts single storey work at £2,200–£3,300 per m² excluding VAT (February 2026), and MyBuilder quotes from about £2,200 per m² for a basic kitchen extension, rising to £3,300+ per m² for complex or premium schemes (August 2026).

Our calculator uses the following 2026 rates for the building element, before regional adjustment:

Finish level	Build cost per m² (ex VAT)	What it typically gets you
Basic	£1,800 – £2,200	Simple rectangle, flat roof, uPVC or standard aluminium doors, one or two rooflights
Standard	£2,200 – £2,700	Aluminium bi-fold or sliding doors, roof lantern, underfloor heating, good-quality finishes
High-end	£2,700 – £3,500	Wide slimline sliders, structural glazing, vaulted or bespoke roof, premium flooring and lighting

Kitchen extension cost by size

The table below shows our calculator’s all-in estimate for a single storey kitchen extension at a standard build finish with a mid-range kitchen in the Midlands. It includes design fees, structural engineer, building control, a lawful development certificate and 20% VAT.

Floor area	Example size	Build only (ex VAT)	All-in with mid-range kitchen, fees & VAT
15m²	3m × 5m	£32,500 – £39,500	£60,000 – £91,500
20m²	4m × 5m	£43,000 – £53,000	£73,500 – £108,500
25m²	5m × 5m	£54,000 – £66,000	£87,000 – £125,500
30m²	5m × 6m	£64,500 – £79,500	£100,500 – £142,500
40m²	5m × 8m	£86,000 – £106,000	£127,000 – £176,500

The kitchen is a fixed lump sum, so on small extensions it is a bigger share of the total. Homebuilding & Renovating’s 30m² example at £66,000–£99,000 plus VAT sits inside our range once VAT is added.

Build cost vs kitchen fit-out: what you are paying for

Choosing the kitchen is where budgets most often drift. Here is how the total for a 25m² extension changes with different combinations of build finish and kitchen budget (Midlands, all-in including fees and VAT):

Build finish	Budget kitchen (£8k–£15k)	Mid-range kitchen (£15k–£30k)	High-end kitchen (£30k–£50k)
Basic	£66,000 – £92,000	£74,500 – £110,000	£92,500 – £134,000
Standard	£78,500 – £107,500	£87,000 – £125,500	£105,000 – £149,500
High-end	£93,500 – £133,000	£102,000 – £151,000	£120,000 – £175,000

What the kitchen budget buys

• Budget (£8,000–£15,000): flat-pack or trade-range units, laminate worktops, standard appliances. MyJobQuote puts basic units at around £3,000–£5,800 and laminate worktops at £20–£40 per m², with fitters charging about £125–£160 a day.
• Mid-range (£15,000–£30,000): rigid or semi-bespoke units, quartz or solid-wood worktops, an island, integrated appliances. Homebuilding & Renovating’s mid-range example budget allows £22,000 for the kitchen.
• High-end (£30,000–£50,000+): bespoke cabinetry, stone or sintered worktops, boiling-water tap, premium appliances and lighting design.

Fitting labour is commonly quoted at 20–30% of the kitchen cost (Which?, cited by the Federation of Master Builders), and retailer-managed installation often excludes plumbing and electrical work, so check what is included.

Kitchen extension cost per m²: what pushes it up

Kitchen extensions cost more per m² than a plain single storey room because of the services and structure involved. These are the items to price individually when comparing quotes.

Opening up the rear wall (open-plan steelwork)

Almost every kitchen diner extension involves knocking through the existing rear wall to join old and new spaces. That wall is load-bearing, so it needs a steel beam (and sometimes a goalpost frame of steel posts) designed by a structural engineer. BestBuilders puts an open-plan kitchen-diner knock-through at £2,500–£4,500 all-in, with wide spans at £4,000–£6,000+ and a goalpost frame adding £1,000–£3,000+. MyJobQuote’s July 2026 figures for supplying and installing a 4–5m beam alone are £900–£1,500, excluding engineer, building control and making good. Ask for it to be itemised on quotes.

Plumbing and drainage moves

Moving the sink is cheap; moving drains is not. MyJobQuote (October 2026) prices a sink move at £400–£750 for a typical relocation, rising to £1,100–£1,600 for an island sink on a concrete or screed floor because the waste pipe has to be chased in with enough fall. Below ground, an extension often has to divert a drain run or reposition a manhole. In Homebuilding & Renovating’s breakdown of a 16.5m² single storey extension, drainage alone came to £3,100. If you build within 3m of a public sewer you will also need a build-over agreement from your water company, which adds time and a fee.

Kitchen extension with bi-fold doors, sliders and rooflights

Glazing is usually the biggest single upgrade in a kitchen extension. Typical 2026 supply-and-fit prices:

Glazing item	Typical cost
Aluminium bi-fold doors, 3 panels (2.1–3.5m)	£3,150 – £4,650
Aluminium bi-fold doors, 5 panels (4.2–5m)	£5,250 – £7,200
uPVC bi-fold doors (1.8–4m)	£1,950 – £4,250
Slimline aluminium sliding doors, 4m wide (fitted)	about £8,350 – £8,900 + VAT
Premium sliding doors, 6m wide (fitted)	about £11,400 – £20,400 + VAT
Aluminium roof lantern (medium, 1.5m × 2m)	£1,900 – £2,300
Timber roof lantern (medium)	£3,200 – £4,200
Flat rooflights (pair, 1m × 1.5m)	£1,800 – £3,000

Bi-folds or sliders? Bi-folds open the whole width, which suits a kitchen that spills onto a terrace in summer. Sliding doors have fewer, larger panes and thinner frames, so they give better views for more of the year, but one panel always stays in place. Wide slimline sliders cost noticeably more. Remember that building regulations limit glazing to roughly 25% of the extension’s floor area (plus any windows lost to the extension) unless your designer shows compliance through an energy calculation, so very glassy schemes may need better-performing glass or extra insulation elsewhere.

Adding a utility room

Many kitchen diner extensions carve out a small utility or boot room. Because it needs its own plumbing, waste, ventilation and electrics, it costs more per m² than open-plan space. Homebuilding & Renovating suggests allowing roughly £500 each for a new sink and taps, extra sockets and an extractor, from about £1,000 for a basic run of units plus fitting, and £300–£1,300 per appliance. As a rough guide, a 3–4m² utility adds the build cost of that floor area plus a few thousand pounds of fit-out.

Kitchen extension cost by region

Labour, access and waste costs vary a lot across the UK. Here is our calculator’s estimate for a 25m² kitchen extension with a mid-range kitchen at a standard finish:

Region	Regional adjustment	25m² kitchen extension, all-in
London	+25%	£105,500 – £149,000
South East	+12%	£96,500 – £138,000
South West & East of England	+4%	£91,000 – £131,000
Midlands	−2%	£87,000 – £125,500
North of England & Wales	−8%	£82,500 – £120,500
Scotland & Northern Ireland	−4%	£85,500 – £124,000

Terraced houses in London often need a side return extension or a wrap-around to create a kitchen diner, both of which cost more per m² than a straightforward rear extension.

Full cost breakdown: fees and extras

Cost item	Typical cost
Design (architect or technologist)	4 – 7% of build cost
Structural engineer (beam and foundation design)	£500 – £2,500
Building control	£600 – £1,200
Lawful development certificate (England)	£274
Householder planning application (England)	£548
Party wall surveyor	£1,000 – £3,000 per neighbour
VAT	20% on building work, fees and kitchen (not the planning fee)
Contingency	10% of build and kitchen

What affects the cost of a kitchen extension?

• Size and shape: a simple rectangle under one flat roof is the cheapest. L-shapes and wrap-arounds add corners, steel and roof complexity.
• Roof type: flat roofs are usually cheaper than pitched or vaulted roofs. See our flat roof extension cost guide.
• Width of the opening: the wider the knock-through, the bigger the steel and the more likely you need a goalpost frame.
• Glazing specification: premium sliders and structural glass can add £10,000+ over standard doors.
• Ground conditions and drains: clay soil, nearby trees and sewers under the footprint mean deeper foundations or diversions.
• Location and access: London and the South East cost 12–25% more on our model; terraced houses without side access add labour.

Do you need planning permission for a kitchen extension?

Many single storey kitchen extensions in England are permitted development. You can usually extend up to 3m from the original rear wall of a semi-detached or terraced house, or 4m for a detached house, with a maximum height of 4m, and eaves no higher than 3m within 2m of a boundary. Under the prior approval scheme (£249) this rises to 6m and 8m. Flats, listed buildings, homes on designated land and areas with Article 4 directions have tighter rules. A lawful development certificate (£274) is worth getting as proof. Read the full rules in our extension planning permission guide.

Whether or not you need planning, you will need building regulations approval for structure, foundations, drainage, insulation, ventilation, glazing and electrics, and you may need to serve party wall notices if you dig foundations near a neighbour’s house or build on the boundary.

How long does a kitchen extension take?

1. Design and drawings: 4–8 weeks
2. Planning or lawful development certificate: around 8 weeks; prior approval up to 42 days
3. Building regulations, structural design and tendering: 4–12 weeks (often overlapping)
4. Build: MyJobQuote puts most kitchen extensions at 5–10 weeks on site, with larger builds taking 3–4 months
5. Kitchen fit: 1–2 weeks after plastering, plus a template-to-fit wait of 1–2 weeks for stone worktops

How to save money on a kitchen extension

• Keep the sink and drains where they are if you can, or plan the new layout around existing runs.
• Build a simple rectangle with a flat roof and one well-placed lantern rather than multiple rooflights.
• Compare bi-folds and sliders on the same width; mid-market aluminium can save thousands over premium brands.
• Buy the kitchen separately and get it fitted independently, but agree who handles plumbing, electrics and making good.
• Stay within permitted development to avoid a full planning application.
• Get a full specification before tendering so three or more builders price exactly the same job.

Does a kitchen extension add value?

Usually, yes, though not always pound for pound. A kitchen diner is one of the most requested features by buyers of family homes. The Federation of Master Builders reports estimates that a kitchen extension can add up to 15% to a property’s value, while MyJobQuote cites a general rule of thumb that adding 10% more floor space adds around 5%. The return is best where the extension fixes a cramped layout and the finished house stays below your street’s ceiling price. A high-end kitchen rarely returns its full cost on sale.

Kitchen extension FAQs

How much does a kitchen extension cost in the UK?

For most homeowners, a single storey kitchen extension costs between about £60,000 and £150,000 all-in in 2026, depending on size, kitchen budget and region. A 25m² kitchen diner with a mid-range kitchen costs roughly £87,000–£125,500 in the Midlands including fees and VAT.

How much does a 4m × 4m kitchen extension cost?

A 16m² single storey extension costs roughly £44,500–£59,000 all-in at a standard finish outside London before the kitchen. Add a mid-range kitchen (£15,000–£30,000 plus VAT) and you are looking at about £62,500–£95,000. See our single storey extension cost guide for more sizes.

Is £50,000 enough for a kitchen extension?

£50,000 including VAT will usually only cover a small extension of around 10–12m² with a budget kitchen outside London. For a typical 20–25m² kitchen diner, budget at least £75,000–£90,000.

How much do bi-fold doors cost in a kitchen extension?

Aluminium bi-fold doors cost about £3,150–£4,650 for a three-panel set and £5,250–£7,200 for a five-panel set up to 5m wide, supplied and fitted. uPVC sets start from about £1,950.

Do I need a structural engineer for a kitchen extension?

Almost always. Opening the rear wall needs a calculated steel beam, and building control will ask for structural calculations for the beam, lintels and foundations. Engineer fees typically run £500–£2,500.

Related guides: Rear extension cost · How to finance an extension · Lawful development certificate

Want the bigger picture? Compare all extension types in our house extension cost guide, or use the cost calculator to test different sizes.

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