Kitchen Extension Cost in London: 2026 Prices Explained

Last updated: 3 October 2026

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A kitchen extension in London is the most common way homeowners add both space and value — and the most expensive per square metre of any single-storey work, because the construction carries a fit-out on top. Nationally a kitchen extension runs at £2,000–£3,000 per m² for construction including VAT. In London, a 20 m² kitchen extension typically costs £55,000–£85,000 for construction alone, before the kitchen itself, and premium schemes push well past £100,000.

The reason is simple: you are paying twice. Once for the fabric of the building, and once for the kitchen units, worktops, appliances and services inside it. Homeowners who budget only the first number are the ones who run out of money at the tiling stage. All figures below are indicative 2026 estimates including VAT at 20%.

Kitchen extension cost at a glance (London)

Apply a London multiplier to the national construction bands. Zones 1–3 sit 30–50% above the national average, so a 20 m² shell that costs £40,000–£60,000 nationally becomes £55,000–£85,000 in inner London. Outer London sits at 20–30% above. The zone distinction matters: access, parking and labour rates are the drivers, and they are worse the closer you are to the centre.

A worked London budget

Take a 20 m² rear and side-return kitchen extension on a Victorian terrace in an inner London borough, mid-range specification:

That lands between roughly £81,000 and £95,000. It is a wide range because the specification spread is wide — and because the fit-out is where homeowners most often overshoot.

What actually moves the number

• Glazing. A 3-metre set of aluminium bi-fold doors costs £3,000–£6,000. A large roof lantern adds £2,000–£5,000. Structural glass roofs run £3,000–£8,000. Glazing is the most expensive element per square metre in the whole project — roughly £1,500–£3,000/m² against £200–£400/m² for brickwork.
• Services relocation. If the extension covers a manhole, or the boiler has to move, budget £1,000–£5,000. Diverting shared drains adds £1,000–£3,000, and a build-over agreement with your water authority is usually required.
• Underfloor heating. £2,000–£4,000 for the extension zone, and popular because it frees wall space for cabinetry. Wet systems cost more up front and less to run.
• Ground conditions. London clay and a high water table can force deeper foundations or piling, adding £3,000–£10,000. A site investigation at £500–£1,500 is worth it before you commit.
• Knocking through. Removing the original rear wall needs steel. Beam installation runs £1,500–£3,000 per beam, with temporary support at £500–£1,000 and making good internal finishes at £1,000–£2,000.
• Kitchen specification. An off-the-shelf kitchen costs £5,000–£8,000; mid-range £12,000–£20,000; bespoke £20,000–£40,000 and up. Worktops alone range from £1,500 to £5,000 depending on laminate versus quartz or sintered stone. Budget £300–£800 per m² of kitchen space as a cross-check.

Planning and permitted development in London

Many London kitchen extensions go through under permitted development: single storey, no more than 3 metres beyond the original rear wall for a terraced or semi-detached house, 4 metres for detached, maximum eaves height of 4 metres, and materials matching the existing house. A side return can often be combined with a rear extension under the same rights, provided the overall footprint stays within the limits.

If you exceed those limits, or your property is in a conservation area or covered by an Article 4 direction, you need householder planning permission at £206 (not subject to VAT), with decisions typically in 8–12 weeks. Larger rear extensions can use the Prior Approval route at £103, which takes around 6–8 weeks and notifies neighbours. If you want certainty for permitted development, a Lawful Development Certificate costs £103.

Regardless of planning, building regulations approval is always required. In London, budget £600–£1,000 through the borough or £900–£1,200 via a private approved inspector. Kitchen extensions specifically trigger Part P electrical certification, ventilation requirements for cooking, and Part L thermal targets. If you are installing a gas hob, the connection must be certified by a registered engineer.

The party wall question

Almost every terraced kitchen extension in London touches the Party Wall etc. Act 1996. Either the new structure ties into a shared wall, or the foundations go deeper than the neighbour's within 3 metres. In outer London budget £1,200–£2,000 for an agreed surveyor; in central and west London £1,500–£2,500. If your neighbour appoints their own surveyor, expect £2,800–£6,000, and a third surveyor adds £500–£1,500.

Serve notices early. A dissenting neighbour is the most common cause of a stalled London kitchen extension, and the notice period alone can cost you two months before anyone lifts a spade.

Timeline — and living through it

Construction typically takes 10–14 weeks for a 20 m² kitchen extension, longer where the side return and rear are combined into a wrap-around. Add 2–4 weeks for drawings and 8–12 weeks for planning if required. The kitchen itself is usually installed in the final three weeks.

Very few homeowners keep a working kitchen throughout. Expect to set up a temporary kitchen in a utility room or dining room — budget £500–£2,000 — and plan for two to four weeks of genuinely disruptive work while the rear wall is opened and services are rerouted. If you can be away for that period, the project is easier on everyone including the trades.

How to spend well

• Design the kitchen layout before the extension is priced. Moving a sink or a range cooker after the drainage is set is expensive.
• Spend on the fabric that is hard to change later — insulation, glazing quality, drainage capacity, floor structure.
• Save on the kitchen furniture itself. A £15,000 kitchen from a quality supplier can look as good as a £30,000 bespoke one if the layout and lighting are right.
• Choose standard unit and worktop sizes. Non-standard dimensions are where kitchens quietly become bespoke.
• Hold a 10–15% contingency untouched. On London projects, something always surfaces.

Getting an accurate London price

Per-m² rates are a sense-check, not a quote. What matters is your address: the ground, the drains, the access, the party wall exposure and the local planning precedent. Our free concept service reads your address, shows what has been approved nearby, and produces concept drawings with an indicative cost. Measured drawings to take to builders come with the Concept package at £995. Design + Planning, which includes the planning application, building regulations drawings and structural engineering, is £2,495. Design to Build, where Suddeco builds it at a fixed quote, starts at £4,500. We work across Greater London only.

Frequently asked questions

How much does a kitchen extension cost in London?

A 20 m² kitchen extension in London typically costs £55,000–£85,000 for construction including VAT, before the kitchen itself. Zones 1–3 run 30–50% above the national average, and premium schemes with high-specification finishes push past £100,000. These are indicative 2026 estimates.

Is the kitchen included in the extension price?

No. Construction and kitchen are separate budgets. A mid-range kitchen with appliances costs £12,000–£20,000, a budget kitchen £8,000–£15,000, and a bespoke kitchen £20,000–£40,000 or more. Budget roughly £300–£800 per m² of kitchen space as a cross-check.

Do I need planning permission for a kitchen extension in London?

If it is a single-storey rear extension within 3 metres for a terrace or semi, or 4 metres for a detached house, it may fall under permitted development. Conservation areas and Article 4 directions change that. Householder planning permission costs £206 and is not subject to VAT.

Why do London kitchen extensions cost so much more?

Labour rates are higher, access is usually restricted, parking and scaffolding need licences, and drainage or services frequently have to be moved. A 20 m² shell costing £40,000–£60,000 nationally becomes £55,000–£85,000 in inner London.

How much does glazing add to a kitchen extension?

A 3-metre aluminium bi-fold set costs £3,000–£6,000. A large roof lantern adds £2,000–£5,000, and a structural glass roof £3,000–£8,000. Glazing is the most expensive element per square metre in the project.

Does a kitchen extension need a party wall agreement?

Almost always on a London terrace. Either the new structure ties into a shared wall, or the foundations go deeper than the neighbour's within 3 metres. Budget £1,200–£2,000 in outer London or £1,500–£2,500 in central London for an agreed surveyor.

How long does a kitchen extension take?

Construction typically takes 10–14 weeks for a 20 m² extension, longer for a combined side return and rear. Add 2–4 weeks for drawings and 8–12 weeks for planning where required. The kitchen is usually installed in the final three weeks.

Can I stay in the house during a kitchen extension?

Most homeowners do, but very few keep a working kitchen. Expect to set up a temporary kitchen at £500–£2,000 and plan for two to four weeks of genuinely disruptive work while the rear wall is opened and services are rerouted.