Kitchen Extension Cost London 2026: Prices, Planning and Design Ideas

A kitchen extension is the most popular reason London homeowners choose to extend their property. Adding space to the kitchen transforms the way a family lives — creating room for a kitchen island, a dining table, a seating area and full-width doors to the garden. In 2026, a kitchen extension in London typically costs between £35,000 and £128,000, depending on size, specification and whether structural alterations to the existing layout are required.

A completed kitchen extension in London by LCCL Construction

LCCL Construction has delivered hundreds of kitchen extensions across London and Hertfordshire. This guide covers kitchen extension costs, what affects the price, planning permission requirements and design ideas to help you get the most from your project.

How Much Does a Kitchen Extension Cost in London in 2026?

Kitchen extension costs in London vary based on the type and size of extension, the specification of glazing and doors, and the complexity of the structural work. Below are typical estimated costs for different kitchen extension types in 2026:

Small kitchen rear extension (up to 3m, 10–15 sqm): £42,000 – £54,000 inc. VAT (£35,000 – £45,000 + VAT). A modest single-storey rear extension that adds a dining area to the back of the kitchen. Suitable for properties with smaller gardens or limited budget.

Side return kitchen extension (15–25 sqm): £42,000 – £72,000 inc. VAT (£35,000 – £60,000 + VAT). The most popular kitchen extension for Victorian and Edwardian terraced houses — filling in the side passage to widen the kitchen significantly. See our full guide to side return extension costs.

Wraparound kitchen extension (25–50 sqm): £66,000 – £144,000 inc. VAT (£55,000 – £120,000 + VAT). The ultimate kitchen transformation — combining a rear extension with the side return to create a full-width open-plan kitchen-diner-living space. See our full guide to wraparound extension costs.

What Is Included in a Kitchen Extension Cost?

A full kitchen extension from LCCL Construction includes architectural drawings, planning permission application where required, structural engineering, building regulations, party wall agreements, all construction work, foundations, roofing, glazing, plastering, electrics, plumbing and decoration. Kitchen units and appliances are typically supplied separately by the homeowner. As a design and build company, we handle every stage under one roof.

What Affects the Cost of a Kitchen Extension in London?

Glazing: The biggest single variable in kitchen extension costs. Full-width bifold doors, large sliding doors or a structural glass roof can add £8,000 to £20,000 to the cost but transform the quality of light and the connection with the garden.

Structural work: Opening up the existing back wall of the house to connect the kitchen with the extension requires structural steel beams. This is standard on most projects and adds £4,800 – £19,200 inc. VAT (£4,000 – £16,000 + VAT) per opening depending on its width — a 3 m opening sits at the bottom of that range, a 7 m box-frame opening at the top.

Underfloor heating: A popular choice for kitchen extensions, adding approximately £3,600 – £7,200 inc. VAT (£3,000 – £6,000 + VAT) to the project cost depending on the floor area.

Roof lantern or skylight: Adding a glazed lantern or large rooflight over the extension brings natural light into the centre of the space — particularly valuable for side return extensions which can otherwise be dark. Adds £3,000 to £8,000 depending on size and specification.

Location: Labour and material costs are higher in inner London boroughs than outer North London areas such as Barnet, Enfield and Haringey. LCCL Construction provides detailed cost estimates across all areas we cover.

Do You Need Planning Permission for a Kitchen Extension in London?

Most single-storey kitchen extensions can be built under permitted development rights without a planning application. However, properties in conservation areas, listed buildings and flats always require planning permission. LCCL Construction checks permitted development eligibility for every project.

For a full breakdown of what you can and cannot build without planning permission, see our guide to permitted development rights for house extensions in London.

Kitchen Extension Design Ideas for London Homes

The best kitchen extensions create a seamless connection between the kitchen, dining area, living space and garden. Key design elements that work particularly well in London kitchen extensions include: full-width bifold or sliding doors to the rear garden, a large central island with seating, a glazed lantern over the dining area for natural light, underfloor heating throughout, and a consistent floor finish running from inside to outside to blur the boundary between the extension and the garden.

How Long Does a Kitchen Extension Take to Build?

A kitchen extension typically takes 10 to 16 weeks to build from the day work starts on site. The full project timeline from initial consultation to completion is usually 5 to 9 months, depending on whether planning permission is required and how long party wall agreements take to finalise.

Why Choose LCCL Construction for Your Kitchen Extension?

LCCL Construction is a specialist house extension builder in London based in Finchley, North London with over 20 years of experience. We have delivered hundreds of kitchen extensions and have over 200 verified reviews at 4.7 out of 5. LABC Award Winners 2024, members of the National Federation of Builders.

Can it be done under permitted development?

A single-storey rear extension of 3 m on a terrace or semi (4 m on a detached house), a side-return infill and a side extension up to half the original width are permitted development on a house outside a conservation area or Article 4 street — no planning application, just a Lawful Development Certificate, which we apply for on every one. Fixed-price permitted development extensions start from £42,000 inc. VAT (£35,000 + VAT) at economy specification, design and build inclusive, and the 6 m / 8 m larger home extension goes through a 42-day prior approval notification rather than a full application. See our permitted development projects page for every product with its from-price and the checks we run before we confirm a project qualifies. Not sure whether your project needs a planning application? Check if you need planning permission

To get a free consultation and detailed cost estimate, call us on 020 8037 7332 or book online to arrange a free consultation call.