Basement Conversion Drawings in Bromley

Which postcode districts around Bromley do we cover for basement conversion work?

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

How does a basement conversion differ street by street across Bromley?

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

• Orpington (BR5, BR6) — a basement conversion in Orpington starts from 1930s semi-detached, and Orpington reads as 1930s semi-detached, post-war. 1930s houses were built without cellars in BR5. Bromley Council assesses Orpington basement conversions against its own Orpington character guidance, and the location plan we draw for Orpington references Orpington High Street.
• Petts Wood (BR5) — a basement conversion in Petts Wood starts from 1930s semi-detached, and Petts Wood reads as 1930s semi-detached, garden suburb. 1930s houses were built without cellars in BR5. Bromley Council assesses Petts Wood basement conversions against its own Petts Wood character guidance, and the location plan we draw for Petts Wood references Petts Wood station.
• West Wickham (BR4) — 1930s semi-detached defines West Wickham, where 1930s semi-detached set what a basement conversion can do. 1930s houses were built without cellars across BR4. Any West Wickham basement conversion is validated by Bromley Council, with West Wickham station the usual West Wickham reference point on the site plan.
• Biggin Hill (TN16) — a basement conversion in Biggin Hill starts from 1930s semi-detached, and Biggin Hill reads as 1930s semi-detached, rural fringe. 1930s houses were built without cellars in TN16. Bromley Council assesses Biggin Hill basement conversions against its own Biggin Hill character guidance, and the location plan we draw for Biggin Hill references Biggin Hill Airport.
• Keston (BR2) — a basement conversion in Keston starts from edwardian villas, 1930s semi-detached, and Keston reads as Edwardian and 1930s village. Edwardian houses rarely have a usable cellar in BR2. Bromley Council assesses Keston basement conversions against its own Keston character guidance, and the location plan we draw for Keston references Keston Ponds.
• Penge (SE20) — basement conversion work in Penge means victorian and edwardian terraces. Penge is Victorian and Edwardian terraces. Victorian cellars here convert without planning permission when the footprint and external appearance are unchanged 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 basement conversion can do. Victorian cellars here convert without planning permission when the footprint and external appearance are unchanged across BR1. Any Bromley basement conversion is validated by Bromley Council, with Bromley High Street the usual Bromley reference point on the site plan.

How do conservation areas and Article 4 affect a basement conversion in Bromley?

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

No blanket Article 4 over Bromley: Bromley Council has not withdrawn permitted development across Bromley, so a basement conversion 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 basement conversion 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 — adjoining Bromley, with 24 conservation areas centred on CR0. A basement conversion on the far side of the Bromley line is determined by Croydon Council, so the Bromley quote for basement conversions is checked against Croydon guidance before it is issued.
• Southwark — the Southwark boundary runs against Bromley, so a basement conversion a street from Bromley is decided by Southwark Council instead. Southwark runs 43 conservation areas across SE1 and its neighbours, which is why basement conversions priced for Bromley are re-checked against Southwark policy whenever the Bromley address sits on that edge.
• Lewisham — cross the Bromley boundary and Lewisham Council takes the basement conversion instead, applying 30 conservation areas of its own around SE3. We re-price basement conversions at the Bromley edge because Lewisham policy and Bromley policy rarely align on basement conversion depth.
• Greenwich — adjoining Bromley, with 20 conservation areas centred on SE3. A basement conversion on the far side of the Bromley line is determined by Greenwich Council, so the Bromley quote for basement conversions is checked against Greenwich guidance before it is issued.

Sources for this Bromley basement conversion 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.