You can extend a house in Barnes, but expect to ask permission for most of it. The area is thick with listed buildings. More than twenty conservation areas overlap it. The ground under it shifts with the weather as well. Neighbours do get extensions through here, after drawings, consultants and a good deal of patience.
Historic England lists 140 buildings in and around Barnes: 18 at Grade I, 14 at Grade II* and 108 at Grade II. Those counts cover a box drawn round the district, so they take in a little of the neighbouring areas too. Listing protects the whole building, inside and out, along with structures attached to it, and almost any change that affects its character needs listed building consent from the council. That includes internal walls, windows and fireplaces as well as extensions. Barnes has had a church on the same spot since the 1100s, and some of the houses round the Green aren't much younger in spirit.
Twenty-two conservation areas fall within the same box, among them Barnes Green, Barnes Common, Castelnau, the Glebe Estate and Cowley Road. In a conservation area the council takes a closer interest in anything visible from the street, from roof shapes to front boundaries, and some changes that are automatic elsewhere need a full application here. Trees are protected too, so the one in the way of the kitchen extension may have more legal standing than the kitchen. Whether a particular house is listed or inside one of these areas changes everything, so look it up on the council's maps and ask the seller for copies of any past planning consents. It's an hour's work that can save a year.
There is one scheduled monument in the area, the strictest tier of protection. It matters mainly to anyone whose land is next to it.
People here keep applying anyway. The council logged 965 planning applications in Barnes between April 2024 and July 2026, 411 of them in the last twelve months. That's a district full of people redoing kitchens, lofts and rear walls through the official route. Whatever you're planning for your house, the planning officer has seen it from the house next door.
The ground has its own say. The British Geological Survey puts Barnes in class 3 for shrink-swell, a published hazard class, and every postcode here reaches it. Shrinkable ground swells when it's wet and shrinks when it's dry, so an extension may need deeper foundations than you'd expect, and the trees nearby matter. Get a structural engineer's view early, so the foundations are designed in from the start and don't turn into a costly surprise halfway through the build. The ground in Barnes moves with the seasons, which is more freedom than the planning system gives anyone above it.
One listed building in the area is on Historic England's Heritage at Risk register. That means its fabric is in poor condition, so any work on it gets close scrutiny and may qualify for grant help. It has no bearing on the rear extension of an ordinary house down the road.
In practice, permitted development rights, which let you make some changes without applying, are narrower in a conservation area and don't cover listed buildings at all. A modest rear extension on an unlisted house outside the conservation areas may still go through without an application. Anywhere else in Barnes, assume you'll need to apply, and build the time and fees into the budget from the start.
Freedom to alter a home in Barnes is poor. The protections are what keep the place looking the way buyers pay for, and they apply just as firmly once the house is yours.