Rear extension in Bromley
Do you need planning permission for a rear extension in Bromley?
Often not, outside the conservation areas and Green Belt — much of Bromley's interwar suburban stock keeps permitted development rights for a single-storey rear extension within the limits, or larger via prior approval. Inside a conservation area or Green Belt, expect a full application (and Green Belt disproportionate-addition tests). The borough's upward-extension and roof-alteration directions do not usually remove ordinary single-storey rear rights outside those designations.
Interwar semis in Bromley, Beckenham and Orpington extend routinely under PD; conservation areas and the Green Belt's disproportionate-addition limits are the exceptions.
Bromley is London's largest, greenest borough: generous interwar plots across Bromley, Beckenham, Orpington and Petts Wood make rear extensions a staple, while more than half the area is Green Belt or Metropolitan Open Land where new building is tightly restricted. It has one of the highest conservation-area counts this site covers, so design scrutiny is real on protected streets. Standard single-storey rear schemes on unconstrained suburban stock remain among the more reliably permitted-development-friendly projects here.
What actually applies in Bromley
Conservation areas in Bromley
Real · planning.data.gov.ukEvery designated conservation area in Bromley from the official dataset — inside one, permitted development narrows and design scrutiny rises.
- Aldersmead Road, Beckenham
- Alexandra Cottages (Parish Lane)
- Barnmead Road, Beckenham
- Beckenham Place Park
- Belvedere Road, Anerley
- Bickley Park
- Biggin Hill RAF Station
- Bromley Common
- Bromley Town Centre
- Bromley, Hayes and Keston Commons
- Broomhill, Orpington
- Cator Road, Sydenham
- Chancery Lane, Beckenham
- Chelsfield
- Chislehurst
- Chislehurst Road, Petts Wood
- Copers Cope
- Crystal Palace Park
- Cudham Village
- Downe
- Downs Hill, Beckenham
- Durham Avenue
- Elm Road
- Farnborough Park
- Farnborough Village
- Garden Road
- Hayes Village
- Keston Park, Farnborough
- Keston Village
- Manor Way, Beckenham
- Mavelstone Road, Bickley
- Nash
- Park Langley, Beckenham
- Penge High Street
- Shortlands
- Southend Road, Beckenham
- St Mary Cray
- St Paul's Cray
- Station Square, Petts Wood
- Sundridge Avenue
- The Broadoaks Estate
- The Chenies, Petts Wood
- The Priory, Orpington
…plus 26 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 Bromley
Real · planning.data.gov.ukNo Article 4 geometry for Bromley appears in the national planning.data.gov.uk dataset, but the borough has made several directions, some of which reach householders: as well as removing office-to-residential and small-HMO conversion rights, Bromley has withdrawn permitted development rights for certain upward (additional-storey) extensions and roof alterations, so those works need planning permission. Green Belt and conservation-area designation are the borough's other major controls. Check the council's Article 4 register for the direction that applies at a given address.
Source: planning.data.gov.uk · Open Government Licence. 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 A) covers single-storey rear extensions up to 3m beyond the original rear wall on attached houses and 4m on detached, with a maximum height of 4m. The 'larger home extension' route extends this to 6m/8m through prior approval with neighbour consultation — but that larger route is not available in conservation areas.
In conservation areas, the basic 3m/4m single-storey rear PD allowance usually survives — what conservation-area status removes is side extensions and two-storey rear extensions. An Article 4 direction can remove more, but Camden's directions in Hampstead and Belsize target front-and-side appearance (solar panels, window changes, boundary treatments), not the single-storey rear allowance. Flats have no PD rights at all. Two-storey rear extensions in conservation areas always need full permission.
Practical rule across London: check the address first. If a conservation area or Article 4 direction applies, budget for a full householder application decided on design, neighbour daylight (the 45-degree test) and materials.
Permitted development limits — rear extension
| Single-storey rear depth — attached house | 3m beyond the original rear wall |
| Single-storey rear depth — detached house | 4m beyond the original rear wall |
| Larger extension via prior approval | 6m attached / 8m detached — not in conservation areas |
| Maximum height (single storey) | 4m |
| Two-storey rear in a conservation area | Full planning permission required |
| Flats | No permitted development rights |
Limits summarise the General Permitted Development Order (Schedule 2, Part 1) as it applies in London. In Bromley, 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 rear extension cost in Bromley?
| Cost per m² (low — straightforward site) | £3,000 |
| Cost per m² (expected) | £3,800 |
| Cost per m² (high — conservation spec, hard access) | £4,600+ |
| Typical build cost (12–18m² single storey) | £36,000 – £83,000 |
| Professional fees, surveys, party wall (add) | 10–18% of build |
Indicative London ranges calibrated from real project data. Conservation-area specifications (matching stock brick, lime mortar, bespoke glazing) and restricted rear access are the two biggest cost drivers. VAT not included.
Realistic timeline
| Design and drawings | 4–8 weeks |
| Planning decision (full application) | 8–12 weeks (8-week statutory target) |
| Prior approval route, where available | 42 days |
| Party wall agreements | 4–10 weeks (parallel) |
| Build | 3–5 months |
What catches people out in Bromley
Assuming the whole borough is Green Belt is wrong — most suburban heartland is not — but missing Green Belt or conservation designation at the address is equally costly. Daylight to neighbours and party wall notices remain routine hold-ups on semis.
Postcode districts in Bromley
BR1 covers Bromley Town Centre and the leafy Sundridge Avenue and Mavelstone Road conservation areas towards Bickley.
BR1 — Bromley & Sundridge →BR2 runs from Bickley Park through Hayes Village to Keston Village and Keston Park, with the Green Belt and the Hayes and Keston commons close by.
BR2 — Hayes, Keston & Bickley →BR3 is Beckenham — the Copers Cope, Cator Road, Park Langley and Beckenham Place Park conservation areas among them.
BR3 — Beckenham →BR6 reaches the Farnborough Village and Chelsfield conservation areas and the rural Green Belt around Downe and Cudham, where new building is tightly restricted.
BR6 — Orpington, Farnborough & Chelsfield →BR7 is Chislehurst — the large Chislehurst conservation area around the commons, with the Petts Wood planned suburb (the Chenies, Station Square) nearby.
BR7 — Chislehurst →SE20 covers Penge and Anerley — the Penge High Street and Belvedere Road conservation areas, with Crystal Palace Park on the boundary.
SE20 — Penge & Anerley →BR4 covers West Wickham and the Hayes fringe in Bromley — interwar semis on generous plots with side access.
BR4 — West Wickham & Hayes fringe →BR5 is Orpington, St Mary Cray and the Petts Wood fringe — classic Bromley suburban stock.
BR5 — Orpington, St Mary Cray & Petts Wood edge →Rear extension in Bromley, asked straight
Do I need planning permission for a rear extension in Bromley?
How much does a rear extension cost in Bromley?
Does Bromley's upward-extension direction stop a single-storey rear?
Is Green Belt a problem for rear extensions?
Do I need a party wall agreement?
What applies at your address?
Borough-level rules only narrow it down. Enter a Bromley 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 Bromley 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.