Loft conversion in Lewisham
Do you need planning permission for a loft conversion in Lewisham?
A staple on the Victorian stock of Brockley, Forest Hill and Sydenham under permitted development outside Article 4 conservation areas. Inside those streets, dormer form is decided through a full application. Building regulations always apply.
A staple on the Victorian stock of Brockley, Forest Hill and Sydenham; the Article 4 conservation areas decide dormer form via a full application.
Rear dormers are a workhorse project on unconstrained terrace roofs. On protected streets, rear-facing, well set-back dormers have a better record than box forms or front alterations. The small-HMO conversion regime is about tenure, not Class B roof enlargements for a single household.
What actually applies in Lewisham
Conservation areas in Lewisham
Real · planning.data.gov.ukEvery designated conservation area in Lewisham from the official dataset — inside one, permitted development narrows and design scrutiny rises.
- Beckenham Place
- Belmont
- Blackheath
- Brockley
- Brookmill Road
- Cobbs Corner
- Culverley Green
- Deptford Creekside
- Deptford High Street & St Pauls Church
- Deptford Town Hall
- Forest Hill
- Halifax
- Hatcham
- Jews Walk
- Ladywell
- Lee Manor
- Lewisham Park
- Mercia Grove
- Perry Vale and Christmas Estate
- Perryfields
- Somerset Gardens
- St Johns
- St Marys
- St Stephens
- Stanstead Grove
- Sydenham Park
- Sydenham Thorpes
- Sydnenham Hill
- Telegraph Hill
…plus 1 further designated areas.
Source: planning.data.gov.uk · Open Government Licence. Boundaries are checked at address level by the area report.
Article 4 directions in Lewisham
Real · planning.data.gov.ukLewisham's Article 4 directions, recorded as around 89 named parcels in the national dataset, fall into two main groups for homeowners: a borough-wide HMO regime (two directions removing the right to convert a house to a small HMO — the southern wards since March 2020, the rest of the borough since January 2024) and conservation-area directions in areas such as Brockley, Brookmill Road, Deptford High Street and Forest Hill that remove householder permitted development. Others cover town centres and employment land. The Alterations and Extensions SPD sets householder design expectations. Use the area report, or the council's Article 4 pages, for the direction that applies at a given address.
Source: planning.data.gov.uk · Open Government Licence · 89 directions recorded. Checked at address level by the area report.
Prices: HM Land Registry UK House Price Index, December 2025 · Open Government Licence.
The planning route — PD or permission?
Permitted development (GPDO Class B) allows roof enlargements up to 40m³ on terraced houses and 50m³ on semis and detached — enough for a substantial rear dormer — provided nothing projects beyond the roof plane of the principal elevation, materials are similar, and dormers sit back from the eaves. Class B is excluded in conservation areas.
In conservation areas the route is a full application, and roof form decides it: rear mansards with traditional slate and proportioned dormers have a strong record on Victorian terraces; box dormers and front-facing alterations are the classic refusals. Article 4 directions (Muswell Hill is the local example) pull roof works into planning control even where conservation policy alone might not.
Whatever the route, building regulations approval is always required — fire escape, stair geometry and floor structure — and a Lawful Development Certificate is cheap insurance on PD schemes.
Permitted development limits — loft conversion
| Roof volume added — terraced house | Up to 40m³ |
| Roof volume added — semi-detached or detached | Up to 50m³ |
| Principal (street-facing) roof plane | No extension beyond it |
| Dormers | Set back from the eaves; materials similar |
| Conservation areas | Class B excluded — full permission |
| Flats | Always need permission |
| Building regulations | Always required, whatever the planning route |
Limits summarise the General Permitted Development Order (Schedule 2, Part 1) as it applies in London. In Lewisham, a conservation area, Article 4 direction or listed status changes the route — the panels above show what is designated, and the address check confirms what applies at your property.
How much does a loft conversion cost in Lewisham?
| Cost per m² (low — rooflight conversion) | £3,000 |
| Cost per m² (expected — rear dormer) | £3,700 |
| Cost per m² (high — mansard, conservation spec) | £4,500+ |
| Typical project (20–28m² with bathroom) | £86,000 – £180,000 |
| Professional fees, surveys, party wall (add) | 8–15% of build |
Mansards in conservation areas sit at the top of the range — natural slate, lead detailing and officer negotiation all cost. Ranges calibrated from real project data; VAT excluded.
Realistic timeline
| Design and drawings | 4–6 weeks |
| PD route (Lawful Development Certificate) | 4–8 weeks |
| Full application (conservation areas) | 8–12 weeks (8-week statutory target) |
| Party wall award | 4–8 weeks (parallel) |
| Build | 10–14 weeks |
What catches people out in Lewisham
Headroom and stair position still filter schemes early. Oversized box dormers and principal-elevation changes are classic refusals on protected streets.
Postcode districts in Lewisham
SE4 is the Brockley conservation area — one of London's largest Victorian conservation areas, with an Article 4 direction removing permitted development, so windows, doors and roof changes need consent.
SE4 — Brockley & Crofton Park →SE13 covers central Lewisham and the Ladywell, Lewisham Park and Lee Manor conservation areas.
SE13 — Lewisham & Ladywell →SE23 is Forest Hill — the Forest Hill conservation area (with Article 4 directions) and Jews Walk, near the Horniman.
SE23 — Forest Hill →SE8 is Deptford — the Deptford High Street and St Paul's and Brookmill Road conservation areas, both with Article 4 directions, plus Deptford Town Hall.
SE8 — Deptford →SE14 covers New Cross and the Telegraph Hill and Hatcham conservation areas — steep Victorian streets above the Thames basin.
SE14 — New Cross & Telegraph Hill →SE6 is Catford and Bellingham — Victorian and interwar terraces with deep side-return and loft precedent in Lewisham.
SE6 — Catford & Bellingham →SE12 covers Lee and Grove Park, spanning Lewisham with Bromley and Greenwich edges.
SE12 — Lee & Grove Park →SE26 is Sydenham and Lower Sydenham — Victorian terraces and larger houses with strong loft conversion activity, spanning Lewisham, Bromley and Southwark edges.
SE26 — Sydenham & Lower Sydenham →Loft conversion in Lewisham, asked straight
Do I need planning permission for a loft conversion in Lewisham?
How much does a loft conversion cost?
What designs get approved in conservation areas?
Is building regulations approval required?
Does the small-HMO conversion regime affect lofts?
What applies at your address?
Borough-level rules only narrow it down. Enter a Lewisham postcode for the live constraint check — conservation area, Article 4 and sold-price comparables, cited to source.
Need it in writing for one address? A planning permission report for a Lewisham property — from £59, or surveyor-reviewed from £295.
Planning Permission Checker provides planning and cost intelligence for early feasibility only. It is not legal, planning, valuation, architectural, structural, or surveying advice. All estimates are indicative and must be verified by qualified professionals before purchase, design, planning submission, or construction.
Cost estimates are indicative only — not a quotation. Final price depends on survey, specification, structure, access, party wall matters, VAT, professional fees, and contractor availability.
Planning outcomes are not guaranteed. Local planning authorities make final decisions.