Kitchen Extension Cost UK: 2026 Prices by Type

A kitchen extension is one of the most popular home improvements in the UK, adding both living space and value, but the cost varies considerably by type, size, location and specification. This 2026 guide covers realistic UK prices for rear extensions, side-return extensions and wrap-around extensions, explains the key cost drivers, and helps you understand what is typically included in a builder's quote before you request your first estimate.

How much does a kitchen extension cost?

A kitchen extension in the UK typically costs £1,500 to £2,500 per square metre in 2026, so a typical single-storey rear kitchen extension runs £30,000 to £70,000. A side-return extension costs £35,000 to £60,000 and a wrap-around extension £60,000 to £100,000. London projects cost roughly 20 to 40 percent more than the UK average.

Use our house extension cost calculator to get a rough figure for your specific floor area and location before contacting builders.

Kitchen extension cost by type

Single-storey rear kitchen extension: £30,000 to £70,000

The most common choice. A single-storey box is added to the back of the property, opening up the existing kitchen or creating a new open-plan kitchen-diner-living space. The wide price range reflects floor area (most rear extensions for a kitchen run 15 to 40 square metres), roof type (flat, lantern or pitched), glazing choices, and finish level. A 20 square metre rear extension at a mid-range spec typically lands at £35,000 to £50,000 including build, structural, basic glazing and a standard finish but before the kitchen itself.

Permitted development rules allow single-storey rear extensions of up to 3 metres on semi-detached and terraced houses, and up to 4 metres on detached houses, without a full planning application (the neighbour consultation scheme applies for extensions between 3 and 8 metres on detached). Larger extensions need householder planning permission. See the full rules on the Planning Portal.

Side-return extension: £35,000 to £60,000

Terraced and semi-detached Victorian and Edwardian houses typically have a narrow side passage running alongside the rear of the property. Infilling this return - usually 2 to 3 metres wide and 4 to 6 metres deep - adds 8 to 18 square metres but transforms the ground floor by squaring off the kitchen footprint, eliminating the dark back room and bringing in light from above via a rooflight or glazed roof. The build cost per square metre for a side-return is higher than a rear extension because the access is tighter and the structural work to remove the existing side wall is more involved. Most side-returns also include a rooflight, which adds cost but is part of what makes the result so effective.

A side-return extension in the UK costs £35,000 to £60,000 finished, with London prices running £45,000 to £80,000. For more detail on all extension types, read our house extension cost guide.

Wrap-around extension: £60,000 to £100,000

A wrap-around combines the rear extension and side-return into one L-shaped structure, giving the maximum ground-floor gain without going up. The overall floor area added is typically 25 to 50 square metres depending on how much of the rear and side are used. Wrap-arounds almost always need householder planning permission because they extend along more than one elevation, and they are the most structurally complex of the three options. A well-designed wrap-around typically creates a single open-plan kitchen, dining and family room that spans the full width and depth of the original house.

Budget £60,000 to £100,000 for a wrap-around extension across the UK, or £80,000 to £135,000 in London. Adding a second storey over the same footprint costs more but yields a bedroom or bathroom upstairs as well - see the section below on other ways to add space.

Kitchen extension cost per square metre

As a cross-check, single-storey kitchen extensions in the UK cost £1,500 to £2,500 per square metre for the structure, drainage connections and standard finishes. The lower end applies to a straightforward flat-roof rear extension in the Midlands or North; the upper end reflects a higher-spec finish, a complex roof, or a project in the South East. Extensions in prime London postcodes sit at the top of the range or above it.

Note that the per-square-metre rate covers the build only. Kitchen units, appliances, flooring and decoration are priced separately and can add £10,000 to £40,000 or more depending on specification.

What is included in a kitchen extension quote?

A detailed quote from a reputable contractor should typically cover:

• Groundworks, foundations and drainage connections
• External walls, insulation and weatherproofing
• Roof structure (flat, lantern, pitched or glazed) and roofing materials
• Structural steel or posts where load-bearing walls are removed
• External doors and standard windows
• First and second fix electrics (consumer unit work, new circuits, sockets and lighting rough-in)
• First and second fix plumbing (supply and waste runs to final positions)
• Plastering, screed and basic floor preparation
• Building Control inspections and sign-off

Items that are usually quoted separately include the kitchen units and appliances, flooring finish, tiles, decoration, bifold or sliding doors (when upgraded from standard), rooflights, underfloor heating, and any landscaping or patio work disturbed by the build. Make sure you understand exactly what is in and out of scope before comparing quotes.

Cost adders: what raises the price

Bifold and sliding doors

Large glazed openings to the garden are by far the most requested upgrade for kitchen extensions. A set of bifold or sliding aluminium doors spanning 3 to 4 metres costs approximately £3,000 to £6,000 supply and fit for standard specifications, rising to £8,000 to £15,000 or more for thermally broken aluminium systems with premium glazing or very wide spans.

Rooflights and glazed roofs

A single fixed rooflight adds roughly £800 to £2,000 installed. A structural glazed lantern over a flat roof costs £3,500 to £8,000 depending on size, and a full-width glazed roof or orangery-style roof with exposed rafters can reach £15,000 to £25,000. Rooflights are particularly valuable in side-return and wrap-around extensions where natural light would otherwise be limited.

Kitchen island

An island is not part of the build cost but is a common addition once the new space is created. A fitted kitchen island ranges from £2,000 for a basic freestanding unit to £15,000 or more for a bespoke fitted island with integrated appliances, stone top and joinery drawers. Plan the island dimensions at the design stage so that drainage and electrical sockets can be run in during the build.

Underfloor heating

Wet (water-fed) underfloor heating adds £80 to £140 per square metre on top of screed costs. For a 25 square metre kitchen extension that is £2,000 to £3,500, plus the manifold connection to the boiler. Electric underfloor heating is cheaper to install at £40 to £80 per square metre but costs more to run long-term. If you are planning underfloor heating, it must be specified before the screed is poured.

Structural work and party wall

Removing a load-bearing rear wall to connect the extension to the existing house adds £1,500 to £4,000 for structural steels and associated structural engineer fees. If your extension is adjacent to a neighbour's boundary, a party wall agreement may be required, which costs £1,000 to £2,500 per affected neighbour if a surveyor is appointed.

Planning permission for a kitchen extension

Many single-storey rear kitchen extensions fall within permitted development rights and do not need a planning application. The key limits for England are:

• Single-storey rear extension: up to 3 metres depth on terraced and semi-detached houses, up to 4 metres on detached houses (up to 6 metres / 8 metres under the neighbour consultation scheme)
• Maximum height 4 metres, or 3 metres within 2 metres of a boundary
• The extension must not cover more than half the area of the original garden
• Materials must be similar in appearance to the existing house
• Different rules apply in conservation areas, listed buildings, Article 4 directions and in Wales, Scotland and Northern Ireland

Side-return and wrap-around extensions are more likely to need planning permission because they extend on more than one elevation. A Certificate of Lawful Development (around £258 application fee in England) is strongly recommended even when permitted development applies, as it provides legal confirmation for mortgage lenders and future buyers. A householder planning application costs the same fee when full permission is needed.

Premium and prime London pricing

In prime central and inner London boroughs - Chelsea, Kensington, Notting Hill, Hampstead, Chiswick, Islington and similar - kitchen extension costs sit materially higher than the national averages above. Access restrictions, parking and skip permits, the ULEZ zone, higher subcontractor rates, longer programme durations and tighter planning constraints all push costs upward. As a guide:

• Single-storey rear kitchen extension in prime London: £50,000 to £110,000
• Side-return extension in prime London: £55,000 to £90,000
• Wrap-around extension in prime London: £90,000 to £150,000+

Design and specification at this end of the market also tend to be higher, with bespoke joinery, stone finishes, full-height glazing systems and underfloor heating throughout. houseUP works as a design-and-build contractor across prime London; visit our house extension service page for project examples and to enquire about a consultation.

Other ways to add space at home

A kitchen extension is not the only way to create more space. A loft conversion adds a bedroom or living room at a similar budget without touching the ground floor. A double-storey extension is worth considering if you also need an extra bedroom - it costs more upfront but the cost per square metre is lower than two separate projects. Each route suits different properties and planning situations.

Plan your kitchen extension with houseUP

houseUP is a design-and-build contractor specialising in kitchen and house extensions across prime London - Chelsea, Kensington, Hampstead, Chiswick and neighbouring boroughs. Our in-house structural engineers and architects handle every stage under a single fixed-price contract, from design and planning through to a fully finished space. Visit our house extension service page to see completed projects, or contact us for a free consultation and quote.

Frequently asked questions

How much does a kitchen extension cost in the UK in 2026?

A single-storey kitchen extension in the UK costs £30,000 to £70,000 in 2026, or £1,500 to £2,500 per square metre. A side-return extension costs £35,000 to £60,000 and a wrap-around extension £60,000 to £100,000. These figures cover the build only and exclude the kitchen units, appliances and decoration.

Does a kitchen extension need planning permission?

Many single-storey rear kitchen extensions are permitted development in England and do not need a planning application, as long as they stay within the depth limits (3 metres for terraced and semi-detached, 4 metres for detached, or up to double under the neighbour consultation scheme), do not exceed 4 metres in height, and do not cover more than half the garden. Side-return and wrap-around extensions are more likely to need full planning permission. Rules differ in Wales, Scotland, Northern Ireland, conservation areas and listed buildings.

How long does a kitchen extension take to build?

A single-storey kitchen extension typically takes 10 to 16 weeks from start on site to practical completion. A side-return takes a similar time. A wrap-around extension may take 14 to 20 weeks. The programme depends on size, structural complexity, the lead times for glazing systems and kitchens, and how quickly your builder can mobilise. Add 4 to 12 weeks before that for design, planning (if required) and building regulations approval.

What is the difference between a rear extension and a side-return extension?

A rear extension is built directly behind the house and increases the depth of the ground floor. A side-return extension infills the narrow alley that runs alongside the kitchen on many Victorian and Edwardian terraced and semi-detached houses, widening the kitchen rather than lengthening it. A wrap-around extension does both, creating an L-shaped addition that maximises the ground-floor footprint.

Does a kitchen extension add value?

A well-designed kitchen extension typically adds 5 to 15 percent to a property's value in the UK, with the higher returns concentrated in areas where buyers pay a significant premium for open-plan space. The return depends on the quality of the design and finish, how the space functions, and the ceiling price in your street. In prime London, a high-quality open-plan kitchen-living extension can add more than its cost to the sale price on the right property.

What is included in a kitchen extension build cost?

A typical build quote includes groundworks, foundations, walls, roof, drainage connections, structural steels, windows, external doors, first and second fix electrics and plumbing, plastering, screed and Building Control. It usually excludes kitchen units and appliances, flooring finishes, tiles, decoration, bifold or sliding door upgrades, rooflights (unless specified), underfloor heating and landscaping. Always confirm what is in scope before comparing quotes from different contractors.