You can extend a house in Herne Hill, but you will rarely be the only one deciding what it looks like. The district is thick with listed buildings. Conservation areas cover much of it. The clay underneath moves with the weather. The neighbours apply for planning permission anyway, by the hundred, and the ones who get what they want are the ones who planned for the wait.
There are 216 listed buildings in and around Herne Hill. One is listed at grade I, six at grade II* and 209 at grade II. Listing covers the whole building, inside and out, so a listed house needs separate listed building consent for work that would be routine anywhere else, from moving a wall to replacing old windows. Owning one makes you the custodian of a small piece of the national record, and the kitchen counts.
The area overlaps 20 conservation areas, including Herne Hill itself, Brockwell Park and Brixton Water Lane. Inside a conservation area the council takes a close interest in anything that changes how a street looks, and some work that would need no application elsewhere does need one here. Herne Hill also straddles the boundary between Lambeth and Southwark, so two councils apply their own planning policies to houses a few streets apart. The quickest useful check is the council's conservation area map for the exact address, because whether a house falls inside a boundary decides how much of the project is yours to decide.
None of this has stopped people trying. The council planning records list 672 applications in the area between April 2024 and June 2026, and 314 of those came in the last twelve months. Herne Hill is full of owners who wanted a bigger kitchen and accepted that the price included a planning file.
The ground is the other thing to plan for. The geological survey's shrink-swell mapping puts the whole area, all of it, in class 3, which means clay soils that swell when wet and shrink when dry. That rarely stops an extension. It does mean a structural engineer should look at foundation depth early, and that nearby trees and drains enter the conversation. The clay was here long before the 1862 railway brought the terraces, and it still has a vote on how deep the new ones go.
Two listed buildings in the area are on Historic England's Heritage at Risk register. That is a list of buildings in poor condition, whose repair can attract grant money and will certainly attract scrutiny. It is a concern for whoever owns those two buildings, not for the buyer of an ordinary terrace on the next street.
In practice, the freedoms most owners elsewhere rely on, the rear extension or the loft conversion that needs no application, are narrower here. A house that is listed or inside a conservation area will often need permission for work that would count as permitted development in a less protected street. Building is still possible. It takes longer, costs more in drawings and fees, and gives the council and the neighbours a chance to comment first.
For anyone buying a house in Herne Hill to reshape it, the freedom to do so is poor, and the plans should be judged by what the council will allow, with the clay underneath having its own say.