What we build in North Harrow
Most North Harrow 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 Metroland semis and detached, larger Arts & Crafts in Pinner.
Extension costs in North Harrow
A mid-spec 25 m² extension in North Harrow typically lands between £86,000 and £141,000 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 £2675–£4075 per m² depending on glazing, structural spans and kitchen spend.
| Project | Size | North Harrow all-in |
|---|---|---|
| Side return infill | 15–20 m² | £65k – £106k |
| Full-width rear | 20–30 m² | £86k – £141k |
| Wraparound | 30–45 m² | £125k – £204k |
| Double-storey rear | 40–60 m² | £168k – £275k |
Planning permission in North Harrow
Pinner and Harrow-on-the-Hill conservation areas add design review. Elsewhere Harrow is a very PD-friendly borough.
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 Harrow 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 neighbour typical.
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
Rear access via a side alley or garden gate speeds up muck-away and cuts labour cost noticeably.
Every quote we issue for North Harrow 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 North Harrow
Well-executed extensions here tend to return a healthy share of their cost at resale, particularly where they add a genuine third or fourth bedroom.
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 North Harrow use us
- KYB-verified builders only
- Live Harrow project experience
- Itemised fixed-price specifications
- Insurance, warranty and accreditation checks