House Extension Drawings in Bromley

Where in Bromley does a house extension actually get determined?

The borough runs from Beckenham out to Biggin Hill, and its postcodes do not behave alike: BR1, BR3 and BR5 sit wholly inside it, while SE20 and SE26 do not. Each row shows the dominant stock and who validates an extension there. Fee columns show the England-wide 2026 statutory charge, not a build estimate.

Which parts of the borough extend most easily?

Bromley is the largest London borough by area and only 49.3% of it is built up, against 66.0% for London as a whole. Plot depth is rarely the binding constraint here. Designation and Green Belt usually are.

• Petts Wood and Orpington (BR5) — interwar semis laid out on generous rear plots, 525 registered sales in 2025 at a median of £460,000, and the fastest-rising median in the borough at 10.2% year on year. The Chislehurst Road conservation area clips 25.2 hectares of Petts Wood but leaves most of the district untouched. This is the classic profile for the prior approval route rather than an application.
• West Wickham (BR4) — the borough's dearest median outside Chislehurst at £685,000 across 219 sales, almost entirely 1930s semi-detached, and effectively free of designation. Rear extensions here are usually a drawing job, not a policy job.
• Beckenham (BR3) — 781 sales, median £545,000, and two designations to check: Park Langley at 32.1 hectares and Manor Way at 15.1. Beckenham also has the highest Flood Zone 2 exposure in the borough, with 14.0% of its postcode units inside it. That does not mean the houses flood; it means a rear extension on one of those units will need a Flood Risk Assessment with the application.
• Chislehurst (BR7) — the 591.5-hectare Chislehurst conservation area is by a wide margin the largest single designation in Bromley and covers most of the residential grid, which is why the median here reaches £652,500. Side extensions and two-storey rear additions are not permitted development inside it, and the officer will expect the roof form to follow what is already there.
• Bromley town and Bickley (BR1) — the only Bromley district where the median fell in 2025, down 1.6% to £450,000, and the one with the largest flat share. Roughly a fifth of BR1 sits in Lewisham, so establish the authority first. Bickley Park adds 22.2 hectares of designation on the eastern side.
• Hayes, Keston and Farnborough (BR2, BR6) — 1,304 sales between them and medians of £553,000 and £570,000. The commons and Keston Park designations sit alongside Green Belt here, and a Green Belt boundary bites harder than a conservation area: it caps the volume of the extension, not just its appearance.
• Biggin Hill (TN16) — 190 sales at £462,250, rural fringe, and the part of the borough where the Green Belt question comes up first rather than last.

What does Bromley policy actually stop you doing?

It stops very little that is genuinely permitted development, and a fair amount that is not. The council refuses under one larger-extension notification in ten. But once a scheme needs a householder application — because it exceeds the depth or height limits, or because the house sits inside one of the 69 conservation areas, or because it is a flat — Bromley is a below-average grantor at 79.8% and a slow one. Its own return shows 185 householder decisions taking longer than thirteen weeks, and 67 of those longer than six months.

Inspectors overturn Bromley more often than they overturn most councils. Of the 1,113 householder appeals decided from Bromley refusals between July 2016 and June 2026, 459 were allowed — 41.2%, against 35.6% for England and a 39.8% median across the London boroughs. That is not an approval rate, and it should not be read as one: only refused applicants appeal, and the great majority never do. What it does say is that a Bromley refusal is worth a second opinion before it is treated as final.

The fabric works in your favour. A quarter of Bromley's 143,430 dwellings — 25.7% — were built between 1930 and 1939, against 16.0% across London, and a further 26.7% between 1945 and 1972. Interwar and post-war semis on wide plots are the easiest stock in London to extend without touching the planning system at all, which is the practical explanation for that 84.9% figure. Only 12.1% of the borough predates 1900, and it is that minority, concentrated in the town centres and Chislehurst, where the designations sit.

How different is it a street over the boundary?

Sharply different, and in Bromley's favour on the prior approval route. The four neighbouring authorities include two of the three toughest larger-extension councils in London.

• Greenwich, across the BR7 edge — refused 47.1% of the 435 larger householder extensions it put through the same procedure, nearly five times Bromley's rate. A Chislehurst-style scheme that clears the notification here can fail a few hundred metres north.
• Lewisham, across SE26 and the northern half of BR1 — 44.3% of 305 refused, and it grants 86.3% of full householder applications, higher than Bromley. The two authorities pull in opposite directions, so on a split postcode the route you choose should follow the authority, not the house.
• Croydon, across SE20 — much closer to Bromley at 15.1% of 529 refused, though it agrees an extension of time on 40.6% of its decisions against Bromley's 30.0%, so the eight-week clock means less there.
• Bexley, across the eastern boundary — 14.9% of 282 refused, and the strongest householder approval rate of the four at 91.7%. On paper the easiest of Bromley's neighbours to get an extension through, on either route.

Sources for this Bromley house 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.