House extension cost
in Barnes.
Barnes — SW13 — village atmosphere within Zone 3, between Hammersmith and Mortlake. Generous Edwardian and inter-war housing, with strong family-buyer demand and consistently high property values.
What makes extension work in Barnes distinct.
Housing: Edwardian and inter-war terraces and semis, plus some Georgian houses around Barnes Pond and the village core.
Planning: Barnes Green and Castelnau conservation areas cover most of the central streets. Article 4 applies in places.
Applications go to LB Richmond upon Thames. We submit on your behalf and handle party wall awards, build-over agreements and conservation officer correspondence end-to-end.
The five extension types — SW13 numbers.
All figures inclusive of design, planning, build, contingency and VAT. The Barnes multiplier (1.05×) 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 Barnes and beyond.
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What Barnes homeowners ask us.
How much does a house extension cost in Barnes in 2026?
Typical 2026 Barnes ranges (inc. design, planning, build, contingency & VAT): side-return extensions £95k–£168k; single-storey rear £116k–£221k; wraparound £179k–£336k; double-storey rear £189k–£399k; basement £263k–£788k. The Barnes multiplier (1.05×) reflects local labour rates, scaffold logistics and finish expectations.
Do I need planning permission for an extension in Barnes?
Barnes Green and Castelnau conservation areas cover most of the central streets. Article 4 applies in places. 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 Richmond upon Thames.
What extension type works best for Barnes houses?
Edwardian and inter-war terraces and semis, plus some Georgian houses around Barnes Pond and the village core. 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 Barnes?
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 Richmond upon Thames processes planning applications in approximately 8–13 weeks depending on backlog.
What hidden costs catch Barnes homeowners out on extensions?
In SW13 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 Barnes extensions?
Yes — Barnes is within our core London catchment. Our studio is at 20 Dawes Road in Fulham, 4.5km from Barnes. We've delivered extensions across the SW13 postcode and our subcontractor network covers Richmond upon Thames. Free site visit, fixed-price quote, 10-year HomePro guarantee on the finished work.
Extension pricing for Barnes’s neighbours.
Twenty minutes on site in Barnes.
On us.
Nick Elias RIBA and Vladimir will visit your Barnes 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 Barnes extension using the same 2026 rate card we quote real clients with.
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