What we build in Harefield
Most Harefield 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 and detached, larger Arts & Crafts in Ruislip and Northwood.
Extension costs in Harefield
A mid-spec 25 m² extension in Harefield typically lands between £85,000 and £140,000 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 £2625–£4000 per m² depending on glazing, structural spans and kitchen spend.
| Project | Size | Harefield all-in |
|---|---|---|
| Side return infill | 15–20 m² | £64k – £105k |
| Full-width rear | 20–30 m² | £85k – £140k |
| Wraparound | 30–45 m² | £123k – £203k |
| Double-storey rear | 40–60 m² | £166k – £273k |
Planning permission in Harefield
One of the most PD-friendly boroughs in London. Northwood and Ruislip Manor conservation areas are the exceptions.
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 Hillingdon and both remove PD rights for rear and side extensions. Our London planning guide walks through the tests in order.
Party wall and neighbours
Semi-detached — one party wall typical, often none for detached homes.
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 Harefield 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 Harefield
Buyers in this area consistently pay a premium for open-plan kitchen-diners with direct garden access.
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 Harefield use us
- KYB-verified builders only
- Live Hillingdon project experience
- Itemised fixed-price specifications
- Insurance, warranty and accreditation checks