Kitchen Extension Chelsea 2026 | Dominant Construction

QUICK ANSWER: A kitchen extension in Chelsea typically costs £70,000–£180,000 for a side return, or £110,000–£250,000 for a full rear extension, depending on size and specification. Most Chelsea properties sit within a conservation area under the Royal Borough of Kensington and Chelsea, meaning full planning permission is standard, and Cadogan Estate freeholder consent applies in addition on much of the borough's land.

Every few years a new extension shape gets declared the future of London kitchens — wraparounds, glass boxes, full-width rear walls of glazing. In Chelsea, none of it has displaced the side return, according to what Dominant Construction sees repeatedly on site. Walk the terraces off King's Road or near Royal Hospital Road and the reason is obvious once you see it: these houses have a narrow alley running down one side, doing nothing except storing bins, and filling it in adds real kitchen width without touching the garden at all.

Chelsea's Victorian terraces were built with a consistent flaw by modern standards — a poky, galley-style kitchen at the rear, with a strip of dead space alongside it that was never designed to be usable. Infilling that side return typically adds 6 to 10 square metres, enough to turn a corridor kitchen into a genuine kitchen-diner, without extending as far into the garden as a full rear extension would.

It's also, in planning terms, often the more straightforward of the two options. A side return generally has less impact on a neighbour's light and outlook than a full-width rear extension, which can make it a smoother conversation with Royal Borough of Kensington and Chelsea planning officers, even though full planning permission is still required in almost every case given the borough's conservation area coverage.

Extension typeTypical 2026 cost (all-in)

Side return extension

£70,000 – £180,000

Full-width rear extension

£110,000 – £250,000

Wraparound (side return + rear combined)

£160,000 – £340,000

These figures include design, planning, and build cost. Chelsea sits above the general London average, reflecting site access constraints on narrow streets like Elystan Street, conservation area material requirements, and the specification level expected — bifold or Crittall-style glazing, engineered stone worktops, and integrated joinery are closer to standard than upgrade here.

Planning permission from the council is only half the picture on much of Chelsea's Cadogan Estate land, where a separate freeholder consent process runs alongside it. Miss this step and it's entirely possible to hold full planning permission and still not be cleared to start work — one of the most common, and most avoidable, ways a Chelsea kitchen extension or conversion project stalls after everything looks approved on paper.

Do I need planning permission for a side return extension in Chelsea? Almost always, yes. Side return extensions typically exceed permitted development limits, and Chelsea's conservation area status removes most of the simplified routes available elsewhere in London.

How long does a kitchen extension take in Chelsea, start to finish? Typically 4–6 months for construction once planning permission is secured, with the planning process itself usually adding 8–12 weeks beforehand.

Is a side return cheaper than a full rear extension? Generally yes, since it adds less floor area, though the per-square-metre cost is often similar — the total cost difference mainly reflects the smaller footprint rather than a cheaper build rate.

Dominant Construction has delivered kitchen extensions and full renovations across Chelsea for over 15 years — FMB-registered, working to JCT contracts, managing planning liaison and construction under one team. Call 020 7118 6155 for a consultation, get in touch online, visit us at 185 Fulham Palace Road, W6 8QX, or see recent projects at dominantconstruction.co.uk.