Usually you can, but in a fair number of streets the council has a say first. Over a hundred buildings in the area are listed. Fourteen conservation areas fall in and around the town. Hundreds of neighbours apply for planning permission every year. And the ground underneath moves. Extending in Bromley is routine, but in some streets it means extra paperwork and a slower process.
The area has 105 listed buildings: three at Grade I, six at Grade II* and 96 at Grade II. Listing protects the whole building, inside and out, so changing a listed home needs listed building consent on top of any planning permission, even for work an ordinary house could do without asking. Most of those 105 are Grade II, the most common grade, and that grade still covers internal walls and replacement windows.
Fourteen conservation areas fall in and around Bromley, including Bromley Town Centre, Bickley Park, Bromley Common and Garden Road. Inside one, the council judges changes by how they affect the look of the street, so things like a new roofline, a front extension or taking down a tree can need permission that would not be needed a few roads away. One side of a boundary can need permission for a dormer while the other side barely needs a builder.
Plenty of people still go ahead. Bromley council's register logged 1,441 planning applications in the area between April 2024 and June 2026, and 640 of them in the last twelve months. Those are applications, and the numbers say nothing about how many were approved. The council's planning register lists what neighbours on the same road applied for and what they got. It is the quickest way to see what that particular street will accept.
The ground is the part buyers tend to miss. Every postcode in the area is rated class 3 for shrink-swell on the geological survey's published hazard scale, the highest class found here. Shrink-swell is clay ground that expands when wet and shrinks when dry, so an extension here usually needs deeper foundations than on firmer ground, and a structural engineer should look at the plans early. Mature trees near the new footings will be the engineer's first question.
Seven listed buildings in the area are on Historic England's Heritage at Risk register. These are buildings in poor condition. Repairing them may qualify for grant money and will certainly get close scrutiny. Their condition is a matter for their owners and Historic England and does not affect the ordinary semi down the road.
In practice, a house that is not listed and sits outside a conservation area can often have smaller work done under permitted development rights, such as a modest rear extension or a loft conversion, without a full application. Those rights are narrower in conservation areas, and on a listed building almost everything needs consent. Around Bromley, start by finding out which of those three categories the house is in.
There is less freedom to extend in Bromley than in most suburbs, because of the conservation areas, the listed buildings and the clay. Larger projects are still possible, but they cost more time and engineering work than buyers usually expect.