How much does a kitchen extension cost UK?

A kitchen extension in the UK typically costs £20,000 to £80,000 depending on size, location, and specification. A small single-storey rear extension (3x3m) costs £20,000–£35,000, a medium extension (4x5m) costs £35,000–£55,000, and a larger extension (5x6m or more) costs £50,000–£80,000+. London and the South East are 20–40% more expensive than the national average.

Do I need planning permission for a kitchen extension?

Many single-storey rear extensions do not need planning permission under permitted development rights. For a detached house, you can extend up to 8 metres to the rear (or 6 metres for semi-detached and terraced). The extension must not cover more than half the garden, must not be higher than 4 metres, and must not extend beyond the side wall. If you exceed these limits, or live in a conservation area or listed building, you will need full planning permission.

How long does a kitchen extension take to build?

A small to medium single-storey kitchen extension typically takes 8 to 14 weeks to build. A larger or more complex extension can take 14 to 20 weeks. This does not include the time for design, planning permission (if needed), Building Regulations approval, and finding a builder, which can add 3 to 6 months before building starts.

Does a kitchen extension add value to your house?

A well-designed kitchen extension typically adds 5–15% to a property's value. For a £300,000 home, that is £15,000 to £45,000. The return on investment is usually higher when the extension creates an open-plan kitchen-diner or adds significant usable floor space. The quality of the finish and how well it integrates with the existing house matters significantly.

How Much Does a Kitchen Extension Cost in the UK?

A kitchen extension is one of the most popular home improvements in the UK. Here is what it actually costs, what affects the price, and how to pay for it.

Kitchen Extension Costs by Size

Extension size	Floor area	Typical cost (exc. kitchen fitting)	Cost inc. new kitchen
Small (3m x 3m)	9 m²	£20,000–£35,000	£28,000–£48,000
Medium (4m x 5m)	20 m²	£35,000–£55,000	£45,000–£70,000
Large (5m x 6m)	30 m²	£50,000–£75,000	£60,000–£95,000
Very large (6m x 8m+)	48+ m²	£70,000–£100,000+	£85,000–£120,000+

These are national averages. London and the South East add 20–40% to these figures.

Cost Per Square Metre

Location	Cost per m² (build only)
North of England	£1,500–£2,200
Midlands	£1,700–£2,400
South of England	£2,000–£2,800
London	£2,500–£3,500+
Scotland	£1,500–£2,200
Wales	£1,500–£2,200

Cost Breakdown

Element	Typical cost	% of total
Foundations and groundwork	£3,000–£8,000	10–15%
Walls and structure	£5,000–£15,000	20–25%
Roof (flat or pitched)	£3,000–£8,000	10–15%
Windows and doors (bi-fold, sliding, etc.)	£3,000–£12,000	10–15%
Electrics	£2,000–£5,000	5–10%
Plumbing and heating	£2,000–£6,000	5–10%
Plastering and decorating	£2,000–£5,000	5–8%
Flooring	£1,000–£4,000	3–5%
New kitchen (units, worktops, appliances)	£5,000–£25,000+	15–25%

What Adds to the Cost

Factor	Additional cost
Bi-fold or sliding doors	£3,000–£8,000 more than standard patio doors
Roof lantern or skylight	£1,500–£5,000 each
Underfloor heating	£1,500–£4,000
Removing a load-bearing wall	£1,500–£4,000 (steelwork and making good)
Poor ground conditions (deeper foundations)	£2,000–£5,000+
Party wall agreement (terraced/semi)	£1,000–£3,000 per neighbour
Architect or designer fees	£2,000–£6,000 (or 7–15% of build cost)
Building Regulations application	£300–£900
Planning permission (if needed)	£260 (householder application, England)

Planning Permission

Situation	Permission needed?
Single-storey rear, within permitted development limits	No (but check with your council)
Extends more than 6m from rear wall (semi/terrace)	Yes — or apply via Prior Approval
Extends more than 8m from rear wall (detached)	Yes
Side extension	May need permission — stricter rules on width
Two-storey extension	Yes
Listed building	Yes, plus Listed Building Consent
Conservation area	Additional restrictions — check with council
Flat or maisonette	Usually need permission

Permitted Development Limits (Single-Storey Rear)

Rule	Limit
Maximum depth (detached)	8m from original rear wall
Maximum depth (semi/terrace)	6m from original rear wall
Maximum height	4m (3m if within 2m of a boundary)
Maximum eaves height	3m
Cannot cover more than	50% of garden area
Must not extend beyond	Side wall facing a highway

You will still need Building Regulations approval even if planning permission is not required.

Build Timeline

Phase	Duration
Design and architecture	2–6 weeks
Planning permission (if needed)	8–13 weeks
Building Regulations application	2–5 weeks
Finding and appointing builder	2–8 weeks
Groundwork and foundations	1–2 weeks
Structure, walls, roof	3–6 weeks
First fix (electrics, plumbing)	1–2 weeks
Plastering, flooring, second fix	2–4 weeks
Kitchen fitting	1–2 weeks
Snagging and completion	1 week
Total (design to completion)	5–9 months

How to Finance a Kitchen Extension

Method	Typical rate	Pros	Cons
Remortgage	4–6%	Lowest rate, long term	Secured against home, fees apply
Further advance from lender	4–6%	Simple if staying with same lender	May not match best market rate
Home improvement loan (unsecured)	6–10%	No home security, fixed repayments	Higher rate, usually max £25,000
0% credit card	0% for 12–24 months	Interest-free period	Low limit, must repay within 0% period
Savings	N/A	No interest cost	Depletes emergency fund

See our remortgage guide and home improvement loan options.

Does a Kitchen Extension Add Value?

Property value	Extension cost	Likely value added	Return on investment
£200,000	£40,000	£15,000–£30,000	35–75%
£300,000	£50,000	£20,000–£45,000	40–90%
£500,000	£70,000	£35,000–£75,000	50–105%

Extensions tend to add more value in higher-value areas and when they create desirable open-plan living space.

Tips for Keeping Costs Down

Tip	Potential saving
Simple rectangular footprint	£2,000–£5,000 vs complex shapes
Standard-size windows and doors	£1,000–£3,000 vs bespoke
Flat roof instead of pitched	£2,000–£5,000
Do decorating yourself	£1,000–£3,000
Compare at least 3 builder quotes	10–20%
Phase the work (build now, fit kitchen later)	Spread cost over time
Off-the-shelf kitchen	£3,000–£10,000 vs bespoke

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