What we build in Forest Hill
Most Forest Hill 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. Victorian terraces (Brockley, Hither Green), Edwardian bays (Forest Hill), 1930s semis in Catford.
Extension costs in Forest Hill
A mid-spec 25 m² extension in Forest Hill typically lands between £107,000 and £162,000 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 £2800–£4300 per m² depending on glazing, structural spans and kitchen spend.
| Project | Size | Forest Hill all-in |
|---|---|---|
| Side return infill | 15–20 m² | £80k – £122k |
| Full-width rear | 20–30 m² | £107k – £162k |
| Wraparound | 30–45 m² | £155k – £235k |
| Double-storey rear | 40–60 m² | £209k – £316k |
Planning permission in Forest Hill
Generally supportive planning. Brockley and Blackheath conservation areas require higher-spec design and materials.
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 Lewisham and both remove PD rights for rear and side extensions. Our London planning guide walks through the tests in order.
Party wall and neighbours
Terrace stock: standard two-neighbour Awards.
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 Forest Hill 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 Forest Hill
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 Forest Hill use us
- KYB-verified builders only
- Live Lewisham project experience
- Itemised fixed-price specifications
- Insurance, warranty and accreditation checks