House extension cost
in Chelsea.
Chelsea — SW3 — sits between Fulham and the King's Road. The housing stock is largely Georgian and early Victorian terraces, often listed, with the mews lanes behind Cheyne Walk and Tite Street providing some of the most architecturally sensitive loft work in London.
What makes extension work in Chelsea distinct.
Housing: Georgian terraces, Victorian stucco-fronted four-storey townhouses, and converted mews — many Grade II listed.
Planning: Cheyne, Chelsea and Hans Town conservation areas cover virtually all of SW3. Listed-building consent is required on a high proportion of properties — mansards are the usual loft route here, never rear dormers.
Applications go to Royal Borough of Kensington & Chelsea. We submit on your behalf and handle party wall awards, build-over agreements and conservation officer correspondence end-to-end.
The five extension types — SW3 numbers.
All figures inclusive of design, planning, build, contingency and VAT. The Chelsea multiplier (1.22×) reflects local labour, scaffolding logistics, conservation requirements and finish expectations.
The 2026 London Extension Cost Guide.
Borough-by-borough pricing, a full £200k cost breakdown, PD vs full planning explained, and the seven hidden costs to watch for in Chelsea and beyond.
Send me the guide.
What Chelsea homeowners ask us.
How much does a house extension cost in Chelsea in 2026?
Typical 2026 Chelsea ranges (inc. design, planning, build, contingency & VAT): side-return extensions £110k–£195k; single-storey rear £134k–£256k; wraparound £207k–£390k; double-storey rear £220k–£464k; basement £305k–£915k. The Chelsea multiplier (1.22×) reflects local labour rates, scaffold logistics and finish expectations.
Do I need planning permission for an extension in Chelsea?
Cheyne, Chelsea and Hans Town conservation areas cover virtually all of SW3. Listed-building consent is required on a high proportion of properties — mansards are the usual loft route here, never rear dormers. Outside conservation areas, single-storey rear extensions up to 3m (terrace/semi) or 4m (detached) usually qualify for permitted development. Side-returns, wraparounds, double-storey extensions and anything in a conservation area need full planning. Applications go to Royal Borough of Kensington & Chelsea.
What extension type works best for Chelsea houses?
Georgian terraces, Victorian stucco-fronted four-storey townhouses, and converted mews — many Grade II listed. On this housing stock, the most common 2VP extension is a single-storey rear or wraparound — adding 20–35 m² of open-plan kitchen-diner. Double-storey extensions become viable on properties with rear gardens deep enough to absorb the additional volume without overshadowing.
How long does an extension take in Chelsea?
Allow 8–12 weeks for design and planning (longer in conservation areas), then 16–22 weeks on site for a single-storey, 22–30 weeks for a wraparound or double-storey, and 28–40 weeks for a basement. Royal Borough of Kensington & Chelsea processes planning applications in approximately 8–13 weeks depending on backlog.
What hidden costs catch Chelsea homeowners out on extensions?
In SW3 the top items are: party wall awards (£1,000–£3,000 per neighbour — common on terraced streets), build-over agreements with Thames Water (£300–£1,500 where drains run beneath the proposed extension), conservation officer consultations, structural engineer fees, drainage and asbestos surveys, and VAT at 20% on top of the base build cost. All of these are itemised in our fixed-price quote.
Does 2VP work on Chelsea extensions?
Yes — Chelsea is within our core London catchment. Our studio is at 20 Dawes Road in Fulham, 1.8km from Chelsea. We've delivered extensions across the SW3 postcode and our subcontractor network covers Kensington & Chelsea. Free site visit, fixed-price quote, 10-year HomePro guarantee on the finished work.
Extension pricing for Chelsea’s neighbours.
Twenty minutes on site in Chelsea.
On us.
Nick Elias RIBA and Vladimir will visit your Chelsea home, walk the site, check planning constraints, advise on PD vs full planning, and give you a realistic budget and programme — even if an extension isn’t the right move.
One number. Sixty seconds. No callback.
Price your Chelsea extension using the same 2026 rate card we quote real clients with.
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