House extension cost
in Clapham Junction.
Clapham Junction — the SW11 streets around the station, often called 'Between the Commons'. One of London's most consistent Victorian terrace grids and one of the busiest loft-conversion markets.
What makes extension work in Clapham Junction distinct.
Housing: Two-storey Victorian terraces with kitchen outriggers — almost uniformly suited to L-shape dormers.
Planning: Most of Between the Commons sits outside the formal conservation areas, so PD rights are intact for standard dormers.
Applications go to LB Wandsworth. We submit on your behalf and handle party wall awards, build-over agreements and conservation officer correspondence end-to-end.
The five extension types — SW11 numbers.
All figures inclusive of design, planning, build, contingency and VAT. The Clapham Junction multiplier (0.96×) 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 Clapham Junction and beyond.
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What Clapham Junction homeowners ask us.
How much does a house extension cost in Clapham Junction in 2026?
Typical 2026 Clapham Junction ranges (inc. design, planning, build, contingency & VAT): side-return extensions £86k–£154k; single-storey rear £106k–£202k; wraparound £163k–£307k; double-storey rear £173k–£365k; basement £240k–£720k. The Clapham Junction multiplier (0.96×) reflects local labour rates, scaffold logistics and finish expectations.
Do I need planning permission for an extension in Clapham Junction?
Most of Between the Commons sits outside the formal conservation areas, so PD rights are intact for standard 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 LB Wandsworth.
What extension type works best for Clapham Junction houses?
Two-storey Victorian terraces with kitchen outriggers — almost uniformly suited to L-shape dormers. 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 Clapham Junction?
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. LB Wandsworth processes planning applications in approximately 8–13 weeks depending on backlog.
What hidden costs catch Clapham Junction homeowners out on extensions?
In SW11 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 Clapham Junction extensions?
Yes — Clapham Junction is within our core London catchment. Our studio is at 20 Dawes Road in Fulham, 3.5km from Clapham Junction. We've delivered extensions across the SW11 postcode and our subcontractor network covers Wandsworth. Free site visit, fixed-price quote, 10-year HomePro guarantee on the finished work.
Extension pricing for Clapham Junction’s neighbours.
Twenty minutes on site in Clapham Junction.
On us.
Nick Elias RIBA and Vladimir will visit your Clapham Junction 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 Clapham Junction extension using the same 2026 rate card we quote real clients with.
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