House extension cost
in Chiswick.
Chiswick — W4 — west along the river from Hammersmith. The Bedford Park estate is England's first garden suburb and one of the most architecturally cohesive Edwardian neighbourhoods in London.
What makes extension work in Chiswick distinct.
Housing: Bedford Park Edwardian villas, Victorian terraces around Turnham Green, and Georgian houses along Chiswick Mall.
Planning: Bedford Park, Chiswick House, Chiswick Mall and Strand-on-the-Green conservation areas cover most of W4. Article 4 directions remove PD rights on Bedford Park.
Applications go to LB Hounslow. We submit on your behalf and handle party wall awards, build-over agreements and conservation officer correspondence end-to-end.
The five extension types — W4 numbers.
All figures inclusive of design, planning, build, contingency and VAT. The Chiswick 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 Chiswick and beyond.
Send me the guide.
What Chiswick homeowners ask us.
How much does a house extension cost in Chiswick in 2026?
Typical 2026 Chiswick 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 Chiswick multiplier (1.05×) reflects local labour rates, scaffold logistics and finish expectations.
Do I need planning permission for an extension in Chiswick?
Bedford Park, Chiswick House, Chiswick Mall and Strand-on-the-Green conservation areas cover most of W4. Article 4 directions remove PD rights on Bedford Park. 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 Hounslow.
What extension type works best for Chiswick houses?
Bedford Park Edwardian villas, Victorian terraces around Turnham Green, and Georgian houses along Chiswick Mall. 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 Chiswick?
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 Hounslow processes planning applications in approximately 8–13 weeks depending on backlog.
What hidden costs catch Chiswick homeowners out on extensions?
In W4 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 Chiswick extensions?
Yes — Chiswick is within our core London catchment. Our studio is at 20 Dawes Road in Fulham, 3.0km from Chiswick. We've delivered extensions across the W4 postcode and our subcontractor network covers Hounslow. Free site visit, fixed-price quote, 10-year HomePro guarantee on the finished work.
Extension pricing for Chiswick’s neighbours.
Twenty minutes on site in Chiswick.
On us.
Nick Elias RIBA and Vladimir will visit your Chiswick 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 Chiswick extension using the same 2026 rate card we quote real clients with.
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