What we build in Brentford
Most Brentford projects we scope fall into three buckets: a side-return or rear infill that fixes a dark galley kitchen, a full-width rear extension that opens the ground floor to the garden, and a rear-plus-loft package that adds a bedroom while the scaffold is already up. 1930s semis, Georgian and Victorian villas in Chiswick, riverside terraces in Isleworth.
Extension costs in Brentford
A mid-spec 25 m² extension in Brentford typically lands between £89,000 and £149,000 all-in — that figure includes professional fees, planning and Building Control, party wall, a 12% contingency and VAT at 20%. Ex-VAT build rates run £2700–£4125 per m² depending on glazing, structural spans and kitchen spend.
| Project | Size | Brentford all-in |
|---|---|---|
| Side return infill | 15–20 m² | £67k – £112k |
| Full-width rear | 20–30 m² | £89k – £149k |
| Wraparound | 30–45 m² | £129k – £216k |
| Double-storey rear | 40–60 m² | £174k – £291k |
Planning permission in Brentford
Chiswick's conservation areas (Bedford Park, Grove Park) demand higher-spec detailing. Elsewhere planning is pragmatic.
Before you assume permitted development applies to your street, check whether your street falls inside a conservation area or an Article 4 direction — both are common in Hounslow and both remove PD rights for rear and side extensions. Our London planning guide walks through the tests in order.
Party wall and neighbours
Chiswick terraces = two party walls; Hounslow semis = one.
Serve notice at least two months before you break ground. Budget £1,200–£2,400 per adjoining owner if they dissent and appoint their own surveyor — see the Party Wall Act guide.
Access, logistics and site set-up
Narrow roads limit lorry size, so materials arrive in smaller loads; a good programme allows for it.
Every quote we issue for Brentford prices skip permits, parking suspensions, protection and welfare explicitly in the preliminaries — so the number you sign is the number you pay.
Value added in Brentford
Light and layout move value here more than raw square metres — spend on glazing and ceiling height.
Typical programme
- Weeks 0–4Measured survey, design and structural calcs
- Weeks 4–12Planning or lawful development certificate, party wall notices
- Weeks 12–16Tender, builder selection and contract signing
- Weeks 16–34On site: groundworks, shell, watertight, first and second fix
- Week 35Building Control sign-off, snagging and handover
Full detail in the London extension timeline guide.
Why homeowners in Brentford use us
- KYB-verified builders only
- Live Hounslow project experience
- Itemised fixed-price specifications
- Insurance, warranty and accreditation checks