House extension cost
in Southfields.
Southfields — SW18 — south of Wandsworth Common towards Wimbledon. The grid between the District Line station and Wimbledon Park is one of the most consistent Edwardian streetscapes in south-west London.
What makes extension work in Southfields distinct.
Housing: Edwardian three-bay terraces with bay windows and tile-hung gables — strong loft potential, often with original outriggers intact.
Planning: Southfields Grid Conservation Area covers the main 'Grid' between the station and Replingham Road. Full planning is the rule rather than the exception.
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 — SW18 numbers.
All figures inclusive of design, planning, build, contingency and VAT. The Southfields multiplier (0.95×) 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 Southfields and beyond.
Send me the guide.
What Southfields homeowners ask us.
How much does a house extension cost in Southfields in 2026?
Typical 2026 Southfields ranges (inc. design, planning, build, contingency & VAT): side-return extensions £86k–£152k; single-storey rear £105k–£200k; wraparound £162k–£304k; double-storey rear £171k–£361k; basement £238k–£713k. The Southfields multiplier (0.95×) reflects local labour rates, scaffold logistics and finish expectations.
Do I need planning permission for an extension in Southfields?
Southfields Grid Conservation Area covers the main 'Grid' between the station and Replingham Road. Full planning is the rule rather than the exception. 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 Southfields houses?
Edwardian three-bay terraces with bay windows and tile-hung gables — strong loft potential, often with original outriggers intact. 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 Southfields?
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 Southfields homeowners out on extensions?
In SW18 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 Southfields extensions?
Yes — Southfields is within our core London catchment. Our studio is at 20 Dawes Road in Fulham, 3.6km from Southfields. We've delivered extensions across the SW18 postcode and our subcontractor network covers Wandsworth. Free site visit, fixed-price quote, 10-year HomePro guarantee on the finished work.
Extension pricing for Southfields’s neighbours.
Twenty minutes on site in Southfields.
On us.
Nick Elias RIBA and Vladimir will visit your Southfields 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 Southfields extension using the same 2026 rate card we quote real clients with.
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