What we build in Old Street
Most Old Street 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. Classic 1840–1880 London stock brick terraces, many in conservation zones.
Extension costs in Old Street
A mid-spec 25 m² extension in Old Street typically lands between £125,000 and £185,000 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 £2975–£4550 per m² depending on glazing, structural spans and kitchen spend.
| Project | Size | Old Street all-in |
|---|---|---|
| Side return infill | 15–20 m² | £94k – £139k |
| Full-width rear | 20–30 m² | £125k – £185k |
| Wraparound | 30–45 m² | £181k – £268k |
| Double-storey rear | 40–60 m² | £244k – £361k |
Planning permission in Old Street
Islington is generally supportive of well-detailed rear/side-return extensions but strict on basement schemes since the 2016 policy tightening. Expect a full application in Barnsbury and Canonbury conservation areas.
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 Islington and both remove PD rights for rear and side extensions. Our London planning guide walks through the tests in order.
Party wall and neighbours
Terraces with vaults under the pavement — expect a section 6 notice on basement work.
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
Tight on-street parking means bay suspensions and timed deliveries — your builder should price this, not absorb it.
Every quote we issue for Old Street 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 Old Street
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 Old Street use us
- KYB-verified builders only
- Live Islington project experience
- Itemised fixed-price specifications
- Insurance, warranty and accreditation checks