Cost Guide · Updated April 2026

How Much Does a Kitchen Extension Cost in 2026? (UK)

A kitchen extension in the UK costs £35,000 to £75,000 in 2026, covering the extension shell and the kitchen fit-out. It's the UK's most popular home improvement — and adds significant value. Here's the full 2026 cost breakdown.

2026 real quotes Updated April 2026 Vetted UK builders
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By the BestBuilders Editorial Team
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Quick Answer

Kitchen extension cost at a glance

A typical kitchen extension in the UK in 2026 costs £35,000–£75,000 — broken down as roughly £1,800–£2,500/m² for the build and £8,000–£30,000 for the kitchen itself.

  • Small kitchen extension (15m²): £35,000 – £50,000
  • Medium kitchen extension (25m²): £50,000 – £75,000
  • Large kitchen-diner extension (40m²): £75,000 – £110,000
  • Side return extension (London terraces): £45,000 – £70,000

London and the South East typically add 20–25%. A kitchen extension adds 10–18% to UK property value — often more than the build cost on properties above £400,000.

Expert Note

The single biggest mistake we see in kitchen-extension quotes

When homeowners approach us about kitchen extensions, around 70% quote a single number they've found online — "I've budgeted £45,000 for a kitchen extension" — and they're usually out by 30–40%. Not because they've been misled, but because the figure they've found is for the extension shell only, not the kitchen inside it. These are two completely separate projects with separate cost structures, and it's the single most expensive misunderstanding we see.

A typical 25m² rear kitchen extension in 2026 breaks down like this: the extension shell (foundations, walls, roof, structural openings, Building Control) is £40,000–£55,000; the kitchen fit-out (units, worktops, appliances, sink, tap, lighting, installation labour) adds £12,000–£35,000 depending on spec; knocking through to join the new space to the existing kitchen adds £2,500–£4,500 in RSJ steels and plaster-work; flooring across the joined space adds £2,000–£5,000. The all-in figure is rarely below £58,000 even for a budget scheme, and hits £95,000+ for a high-specification kitchen-diner with bifolds, a lantern roof and a decent appliance package.

The fix: when you ask builders for a quote, be explicit about what's included. Ask for "extension shell + kitchen fit-out combined" or "extension shell only — kitchen priced separately" and compare like with like. The worst budget blow-ups we see are homeowners who agree a £48,000 shell-only quote, realise three months in that the kitchen itself is another £20,000+, and can't stop the build. Plan the full number from day one.

Written by the BestBuilders Editorial Team. Based on platform quote data, industry research and primary UK source material. Reviewed 20 April 2026. Questions: info@bestbuilders.co.uk.

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Full Cost Breakdown

2026 Kitchen Extension — Shell + Fit-Out Split

A kitchen extension has two parts: the extension itself (shell) and the kitchen (fit-out). Most homeowners underestimate the fit-out cost. Here's a realistic 2026 split.

Element Budget Spec Mid-Range High-End
Extension shell (20m²) £36,000 £45,000 £55,000
Kitchen units & worktops £5,000 £12,000 £25,000
Appliances £1,800 £4,500 £10,000
Flooring (LVT / tile / engineered wood) £1,200 £2,400 £4,800
Bifold / sliding doors £3,500 £6,500 £12,000
Lantern / skylights £0 £2,500 £6,000
Underfloor heating £0 £1,800 £3,500
Total (20m² kitchen extension) £47,500 £74,700 £116,300

Prices include all labour, materials, building control and VAT. Add 10% contingency. Regional variation: +25% London, −10% to −15% North England, Wales and Scotland.

By Extension Type

Kitchen Extension Types & 2026 Prices

Rear Extension

Most popular — full kitchen-diner

£50,000 – £85,000

Build onto the back of the house to create an open-plan kitchen-dining space. Usually under Permitted Development. The gold standard for UK family homes.

Side Return

London terrace classic

£45,000 – £70,000

Extends into the unused side passage. Transforms dark Victorian kitchens into bright, wide open-plan spaces. Typical 5–6m² uplift.

Wrap-Around

Maximum kitchen space

£85,000 – £140,000

Rear + side combined. Creates the largest open-plan kitchen-living space possible on a single floor. Planning usually required.

Single-Storey

Classic family extension

£45,000 – £80,000

Generic single-storey rear extension used for a new kitchen. Flat roof or pitched, with glazing to the garden.

Double-Storey

Kitchen + bedroom above

£90,000 – £160,000

Kitchen-diner downstairs plus an extra bedroom or ensuite above. Best value per m² — shares foundations and roof with existing house.

Conservatory-Style

Lower-cost alternative

£18,000 – £35,000

Solid-roof orangery or conservatory extension. Usable year-round with underfloor heating. Limits kitchen layout flexibility.

£2,100
Avg cost per m² (2026)
14wk
Typical build time
15%
Property value uplift
#1
UK home improvement for ROI
Budget Tips

How to Save £5,000–£15,000 on a Kitchen Extension in 2026

Kitchen extensions are where budgets most often slip. Here are six specific moves that save UK homeowners thousands in 2026 without compromising the finished result:

  • Get 3 quotes, not 1. Prices vary 20–30% between builders for identical specs — a £60,000 job can come in at £48,000 from a different quote. Free to do, saves thousands.
  • Stay within Permitted Development. Avoid a £258 planning fee plus £2,000–£4,000 of architect resubmissions. PD also saves 8–12 weeks of project time.
  • Choose flat roof over pitched. A GRP or EPDM flat roof is £3,000–£6,000 cheaper than a pitched roof for the same footprint — and modern finishes look sharp.
  • Skip the roof lantern. Lanterns add £3,000–£6,000. Two well-placed Velux rooflights give similar daylighting at a third of the cost.
  • Supply your own kitchen. Buying units direct from Howdens/Wren/Magnet and asking your builder to install can save £3,000–£8,000 vs a turnkey kitchen specialist.
  • Time the build for spring. January–March is builder low season — expect 5–10% lower quotes. Avoid October–December when everyone wants work done before Christmas.
Related Guides
All cost guides →
Rear Extension

Rear Extension Cost 2026

£27k – £100k

Full guide to rear extension costs by size with regional data.

See prices ›
Loft

Loft Conversion Cost 2026

£20k – £85k

Loft conversion costs by type — Velux, dormer, hip-to-gable, mansard.

See prices ›
Kitchen Only

Kitchen Renovation Cost

£8k – £30k

Costs for a new kitchen without extending — units, worktops, fit.

Compare kitchen prices ›
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Frequently Asked Questions

Kitchen Extension Cost FAQs

A 5m x 5m (25m²) kitchen extension typically costs £55,000–£80,000 in 2026, including the extension shell and mid-range kitchen fit-out. London and the South East push this to £68,000–£100,000. The figure covers structural work, bifold doors, flooring, units, worktops and standard appliances, but excludes high-spec extras like lantern roofs or bespoke joinery.
Many single-storey rear or side kitchen extensions fall under Permitted Development and don't need planning permission — provided you stay within size limits (4m rear depth detached, 3m semi/terrace), don't exceed 4m height, and aren't in a conservation area. Double-storey or wrap-around extensions typically need full planning. Check eligibility with a Lawful Development Certificate (£129) to protect the investment when selling.
On a typical £60,000 kitchen extension, the split is usually: £40,000–£45,000 for the extension shell (foundations, walls, roof, glazing, electrics, plastering) and £15,000–£20,000 for the kitchen itself (units, worktops, appliances, flooring, tiling). Premium kitchens can flip this ratio — high-end kitchens reach £30,000+ just for the fit-out.
A typical kitchen extension takes 12–16 weeks on site, including the shell build and kitchen fit-out. Add 8–12 weeks upfront for architect drawings, planning (if needed) and Building Control. Budget 6 months from first design meeting to final handover. Expect to live without a kitchen for roughly 4–6 weeks during the fit-out phase — plan a temporary kitchen in another room.
Yes — kitchen extensions consistently deliver one of the highest returns on investment of any UK home improvement. They typically add 10–18% to property value, meaning on a £400,000 home, a £60,000 extension adds £40,000–£72,000 in value. Even on the lower end, most homeowners fully recoup costs on sale, plus get years of enjoyment from the improved space.
Yes — kitchen extension costs have risen approximately 4–6% in 2026 versus 2025. Labour rates are up around 5%, glazing is up 3%, and updated Building Regulations Part L adds £1,200–£2,000 for improved insulation and air-tightness. However, brick, timber, steel and kitchen unit prices have stabilised after the 2023–24 spike. Budget 5% extra compared to 2024 quotes.
A rough rule of thumb: 20–35% of your total kitchen-extension budget should go on the kitchen fit-out (units, worktops, appliances, installation), with the remaining 65–80% on the extension shell. On a £70,000 total budget, that's £14,000–£24,500 for the kitchen itself. Going below 20% usually means a budget-line kitchen that looks out of place in a freshly built extension; going above 35% means you're funding luxury appliances at the expense of the building envelope, which is rarely the right trade-off. The highest-ROI configuration we see is a mid-range kitchen (£15,000–£22,000) with one 'hero' appliance (typically a £2,500–£4,000 induction hob with downdraft, or a large-format American-style fridge).
Usually yes — and we'd recommend it for cost and convenience. Standard practice is to build the extension shell first (8–12 weeks) with the existing kitchen untouched, then knock through and fit the new kitchen in a second phase (3–5 weeks). During the knock-through phase itself (3–7 days), you'll be without a kitchen. Most builders will set up a temporary kitchen in the utility room, garage or even dining room using a microwave, slow cooker, kettle and a plug-in induction hob — £300–£600 of temporary kit. This saves £3,000–£6,000 versus renting temporary accommodation for the build duration.
Yes — always. Permitted Development only covers planning, not Building Regulations. Every kitchen extension needs a full Building Control application (either local authority or Approved Inspector), with inspections at foundations, damp-proof course, drainage, insulation, superstructure and completion. Fees range from £800 to £1,800 depending on size and local authority. Your builder or architect will handle the application on your behalf, but the homeowner is the "person carrying out the work" under the regulations and is ultimately responsible if work is non-compliant. Always insist on receiving the Final Certificate at completion and file it with your house paperwork.
A mid-range kitchen extension costs £2,200–£2,900 per m² for the building shell alone in 2026 — slightly above a standard rear extension because kitchen-specific works (upgraded drainage, additional gas and electrical capacity, stronger floor loadings for island units, extra glazing for light) add cost. Add £800–£1,500 per m² for the fitted kitchen itself (cabinets, worktops, appliances, fitting), making the total supplied-and-fitted rate £3,000–£4,400 per m². London and the South East add 25–40% to both figures.
A small kitchen extension of 8–12m² — usually infilling a side return or a modest rear bump-out — typically costs £22,000–£34,000 building-only in 2026, plus £8,000–£18,000 for the fitted kitchen to finish. The smaller footprint has a slightly higher per-m² rate (foundations, roof and drainage have fixed base costs). Full project budget including professional fees and 12% contingency usually comes in at £38,000–£58,000. Side-return extensions on Victorian terraces fall in this category.
An island adds £3,500–£12,000 to the fitted-kitchen budget versus a galley or L-shape layout without one. The island itself is usually cabinets (£1,500–£5,000), a continuous worktop (£1,200–£4,000 in quartz or similar), and additional plumbing or electrics if it houses a sink or hob (£500–£1,500). Kitchens with island units also typically need 18m²+ of floor area to be comfortable — driving up the extension size and cost. For an island hob you need a downdraft extractor (£1,500–£3,500) or a ceiling-mounted extractor with ducting (£1,200–£2,800).
A side-return kitchen extension on a Victorian or Edwardian terrace typically costs £36,000–£62,000 for build only in 2026, on a footprint of 10–16m². Add £10,000–£22,000 for the fitted kitchen. Side returns have extra structural cost (replacing the load-bearing wall needs a steel beam, party wall agreements are usually needed, existing drain runs almost always need diverting) — typically adding £4,000–£9,000 over an equivalent-size rear extension. Full project budget with fees and contingency usually lands at £55,000–£92,000.
Sources & Further Reading

Our sources for this guide

Every figure in this guide is cross-referenced against primary UK sources. We cite the specific documents and data providers we used so you can verify and dig deeper.

Links open in a new tab on external sites. We do not benefit commercially from any of these links; they are included to help readers verify claims and research further. If you spot a broken or outdated link, email info@bestbuilders.co.uk.

About This Guide

Editorial standards & how to reach us

This guide was researched, written and fact-checked by the BestBuilders Editorial Team. Every figure is cross-referenced against primary UK sources (gov.uk, Ofgem, RICS BCIS, FMB, MCS), verified quote data from vetted contractors on our platform, and independent industry reports. Guides are reviewed at least quarterly to reflect current market conditions and regulations.

Spotted something out of date? We care about accuracy. Email info@bestbuilders.co.uk or call 0800 852 7782 and we'll review it — most corrections go live within 48 hours.

BestBuilders Editorial Team
UK-based · Reviewed 20 April 2026
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