Yes, in most of West Wickham you can extend your house, though the rules are tighter in some places than a plain 1930s suburb suggests. Listed buildings here are few, and almost all of them are at the lowest grade. A handful of conservation areas cover parts of the wider district. The neighbours apply for planning permission constantly. The clay underneath is the real limit on what you can build.
The wider area contains 28 listed buildings. One is Grade I, two are Grade II* and the other 25 are Grade II. Owning a listed building means needing consent for almost any change, inside or out, including the sort of thing an ordinary owner would never think to ask about. Twenty-eight in a suburb of this size means most buyers will never own one. The one Grade I building dates from the fifteenth century and has been everything from a Tudor manor to a hotel to a school. None of its owners has been allowed to fit a bifold door to it.
Six conservation areas fall within the box drawn around West Wickham. Their names, Hayes Village and Bromley, Hayes and Keston Commons among them, show that several belong mostly to the neighbouring districts. Inside one, the council looks harder at changes to the front of a house and at anything visible from the street. Some works that would go through without an application elsewhere will need consent there.
There is one scheduled monument in the area. The named sites for the district include a Romano-British site at Wickham Court Farm. Scheduling is the strictest protection there is, but it only matters if the land you want to dig into is part of one.
People here alter their homes all the time. Bromley council received 535 planning applications for the area between April 2024 and June 2026, including 250 in the last twelve months. That is a borough handling a steady flow of rear extensions, loft conversions and side additions to semis built for a different idea of how much space a family needs. Look up the house's own planning history on the council's portal. If the semi next door already has a two-storey side extension, you will know what has been allowed on that street.
The ground is the real constraint. The British Geological Survey's shrink-swell hazard reaches class 3 across the whole area. That means clay that swells when wet and shrinks when dry, enough to shift shallow foundations. It does not stop an extension. It does mean deeper foundations than a builder working on gravel would quote for, and a structural engineer's view before you sign off the design. Large trees near the footings can make the movement worse, so ask about them early.
One listed building in the area is on Historic England's Heritage at Risk register. That means it is in poor condition, and any repair will get grant interest and close attention from the authorities. Neither touches the buyer of an ordinary house on an ordinary road.
For a typical inter-war semi outside a conservation area, much of the usual rear and loft work can be done under permitted development, without a full application, provided it stays within the national limits. Inside a conservation area, or on a listed building, those limits shrink or disappear and a full application is needed. Whichever applies, building regulations still cover the foundations, and with this clay that is where the bill grows.
Your freedom to extend in West Wickham is average. Most semis can grow at the back and in the roof without much trouble, but a few streets carry extra rules and the clay under all of them makes every extension a foundation job.