Kitchen Extension Cost in London 2026: What to Budget
A kitchen extension is one of the most popular home improvements in London, and one of the most widely mis-budgeted. Figures quoted online range from £30,000 to well over £150,000 — and both ends of that range can be accurate, depending on what the project actually involves. This guide cuts through the noise with a realistic breakdown of what drives kitchen extension costs in London in 2026.
What a Kitchen Extension Actually Includes
When clients budget for a kitchen extension, they often think primarily about the structure — the new walls, roof, and floor. But the kitchen extension is almost always a package that includes: structural works (new foundations, steelwork for any openings, new roof structure); external envelope (walls, roof covering, glazing, and any bi-fold or sliding door system); internal fit-out (insulation, plastering, floor screed, electrical, and plumbing for the kitchen); kitchen supply and installation (if not client-supplied); and external works (any changes to paving, drainage, or the rear garden affected by the build).
Missing any of these categories from the initial budget is how kitchen extensions consistently come in "over budget" — the budget was never complete.
Cost Ranges for Kitchen Extensions in London 2026
Small single-storey rear extension (3m x 3m to 4m x 4m): Build-only cost (excluding kitchen): £40,000–£60,000. With a mid-range kitchen supply and installation: £55,000–£75,000.
Medium single-storey rear extension (4m x 5m to 5m x 6m): Build-only cost (excluding kitchen): £60,000–£90,000. With a mid-range kitchen: £75,000–£110,000.
Larger single-storey extension (6m+) or wrap-around: Build cost from £90,000–£150,000+, depending on structural complexity, glazing specification, and finishes.
These figures assume London labour rates and reflect Q3 2026 market pricing. VAT is additional for VAT-registered contractors.
What Pushes the Cost Up
Structural openings into the existing house. Creating a wide open-plan connection between the new extension and the original kitchen often requires a large steel beam. Structural steelwork and associated temporary support works add cost — typically £3,000–£8,000 for a standard opening.
Glazing specification. Aluminium bi-fold or sliding door systems in a 4–5m opening typically cost £6,000–£12,000 supplied and installed. Skylights add further cost.
Drainage diversions. If the extension footprint affects existing drainage runs, a drainage diversion may be required. This is often discovered once enabling works begin.
Party wall issues. Where the extension builds to or near the boundary, party wall agreements with neighbours add time and professional fees — typically £800–£2,000 per neighbour.
Kitchen quality. A mid-range kitchen (Howdens, Wren, or similar) runs £8,000–£20,000 supplied and fitted. A bespoke or high-specification kitchen can reach £40,000–£80,000 or beyond.
How to Budget Properly
Get a scope of works before you get prices. Ask every contractor to confirm exactly what their figure includes and excludes. Make sure the scope covers structure, envelope, M&E, finishes, kitchen installation, and external works. Then add a 10–15% contingency for unforeseen items once the ground opens or the walls come down.
RCB Design & Build handles kitchen extensions across London as a principal contractor — from the first design meeting through to final handover. Contact us for a properly structured estimate based on your specific project.
07359 872594 | contact@rcbgroup.co.uk | www.rcbgroup.co.uk