What we build in Blackheath
Most Blackheath 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 Blackheath
A mid-spec 25 m² extension in Blackheath typically lands between £105,000 and £160,000 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 | Blackheath all-in |
|---|---|---|
| Rooflight conversion | 15–20 m² | £58k – £88k |
| Rear dormer kit | 20–28 m² | £105k – £160k |
| L-shaped dormer kit | 28–36 m² | £142k – £216k |
| Hip-to-gable + dormer | 30–40 m² | £158k – £240k |
Planning permission in Blackheath
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 Blackheath 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 Blackheath
Adding floor area is usually cheaper than moving once stamp duty, agent fees and moving costs are counted.
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 Blackheath use us
- KYB-verified builders only
- Live Lewisham project experience
- Itemised fixed-price specifications
- Insurance, warranty and accreditation checks