Mansard Roof Extensions in Bromley

Which postcode districts around Bromley do we cover for mansard roof extension work?

Every Bromley postcode district we draw in, the stock that dominates it and the authority that validates a mansard roof extension there. Bromley fees below are the statutory England rates for 2026, not mansard roof extension estimates.

What changes about a mansard roof extension in each part of Bromley?

Roof pitch, wall build-up and plot depth change every few Bromley streets, and each one changes what a mansard roof extension can achieve at that address.

• Biggin Hill (TN16) — mansard roof extension work in Biggin Hill means 1930s semi-detached. Biggin Hill is 1930s semi-detached, rural fringe. Mansards are rare on 1930s stock — the hipped roof form works against the geometry throughout TN16. Bromley Council decides the Biggin Hill application, and Biggin Hill Airport anchors the Biggin Hill location plan.
• Keston (BR2) — mansard roof extension work in Keston means edwardian villas, 1930s semi-detached. Keston is Edwardian and 1930s village. Edwardian parapets give a mansard a clean base line throughout BR2. Bromley Council decides the Keston application, and Keston Ponds anchors the Keston location plan.
• Penge (SE20) — mansard roof extension work in Penge means victorian and edwardian terraces. Penge is Victorian and Edwardian terraces. A mansard on a Victorian terrace almost always needs full planning permission throughout SE20. Bromley Council decides the Penge application, and Penge East station anchors the Penge location plan.
• Bromley (BR1, BR2) — Victorian and Edwardian centre defines Bromley, where victorian terraces, edwardian villas, post-war flats set what a mansard roof extension can do. A mansard on a Victorian terrace almost always needs full planning permission across BR1. Any Bromley mansard roof extension is validated by Bromley Council, with Bromley High Street the usual Bromley reference point on the site plan.
• Beckenham (BR3) — Edwardian villas, 1930s semi-detached defines Beckenham, where edwardian villas, 1930s semi-detached set what a mansard roof extension can do. Edwardian parapets give a mansard a clean base line across BR3. Any Beckenham mansard roof extension is validated by Bromley Council, with Beckenham Junction the usual Beckenham reference point on the site plan.
• Chislehurst (BR7) — Large 1930s detached, conservation defines Chislehurst, where 1930s detached, edwardian villas set what a mansard roof extension can do. Edwardian parapets give a mansard a clean base line across BR7. Any Chislehurst mansard roof extension is validated by Bromley Council, with Chislehurst Caves the usual Chislehurst reference point on the site plan.
• Bickley (BR1) — 1930s detached, conservation defines Bickley, where 1930s detached, edwardian villas set what a mansard roof extension can do. Edwardian parapets give a mansard a clean base line across BR1. Any Bickley mansard roof extension is validated by Bromley Council, with Bickley station the usual Bickley reference point on the site plan.

Does Bromley planning policy restrict a mansard roof extension?

Bromley conservation designations: there are 48 across Bromley Council, Beckenham, Keston, Bickley among them. Designation costs a Bromley owner the permitted-development route: a mansard roof extension then needs a £548 householder application over 8 weeks, in place of the £249 prior approval route that takes 6 weeks. Keston is the Bromley designation that most often changes a mansard roof extension design.

No blanket Article 4 over Bromley: Bromley Council has not withdrawn permitted development across Bromley, so a mansard roof extension outside a Bromley conservation area usually keeps it. The £274 Lawful Development Certificate is still the document a SE20 owner wants on file.

What Bromley is built from: Large 1930s detached and semi-detached in Chislehurst and Bickley; Edwardian in Beckenham; Victorian in Bromley town; Metropolitan Green Belt covers significant rural-fringe land. Largest London borough by area; substantial Green Belt; conservation areas in most town centres; generally permissive elsewhere. That mix decides the mansard roof extension route in Bromley more than the postcode does, and it is what a Bromley Council case officer reads first. A householder application costs £548 paid to Bromley Council direct, with 8 weeks to a decision once validated.

What happens if a Bromley property sits on a boundary?

• Croydon — cross the Bromley boundary and Croydon Council takes the mansard roof extension instead, applying 24 conservation areas of its own around CR0. We re-price mansard roof extensions at the Bromley edge because Croydon policy and Bromley policy rarely align on mansard roof extension depth.
• Southwark — the Southwark boundary runs against Bromley, so a mansard roof extension a street from Bromley is decided by Southwark Council instead. Southwark runs 43 conservation areas across SE1 and its neighbours, which is why mansard roof extensions priced for Bromley are re-checked against Southwark policy whenever the Bromley address sits on that edge.
• Lewisham — the Lewisham boundary runs against Bromley, so a mansard roof extension a street from Bromley is decided by Lewisham Council instead. Lewisham runs 30 conservation areas across SE3 and its neighbours, which is why mansard roof extensions priced for Bromley are re-checked against Lewisham policy whenever the Bromley address sits on that edge.
• Greenwich — the Greenwich boundary runs against Bromley, so a mansard roof extension a street from Bromley is decided by Greenwich Council instead. Greenwich runs 20 conservation areas across SE3 and its neighbours, which is why mansard roof extensions priced for Bromley are re-checked against Greenwich policy whenever the Bromley address sits on that edge.

Sources for this Bromley mansard roof extension page: borough policies maps and conservation-area registers (2025–26), Royal Mail postcode district boundaries, the Town and Country Planning (Fees for Applications) (England) Regulations, the Town and Country Planning (General Permitted Development) (England) Order 2015 as amended, and the Party Wall etc. Act 1996.