Yes, but plan on paperwork and patience. Hundreds of listed buildings stand in and around Ham. Dozens of conservation areas overlap it. The clay underneath has views of its own. The neighbours still apply for planning permission by the hundred, so it can be done, and it takes a while.
The wider area this page measures holds 463 listed buildings. Twelve are Grade I, 55 are Grade II* and 396 are Grade II. Listing covers the inside of a building as well as the outside, so a new kitchen, a replacement window or a moved wall can each need listed building consent on top of any planning permission, and work done without it is a criminal matter. If your house is one of the 463, the council will have an opinion on the windows.
The same area takes in 45 conservation areas, including Ham Common, Petersham and the Parkleys Estate. Inside one, more work needs consent than it would elsewhere. Changes visible from the street, demolition and work to trees all get a closer look, and the council judges whether a design keeps the character of the area. A 1950s estate made the conservation list here, so in Ham even modern architecture counts as heritage.
There are also 4 scheduled monuments in the area, the strictest tier of protection. They matter mainly to anyone whose land borders one, and that will be very few buyers.
None of this has stopped people trying. The council logged 1,323 planning applications for the area between April 2024 and July 2026, with 529 in the most recent twelve months. That is a steady stream of extensions, loft conversions and alterations from neighbours who decided the forms were worth filling in. The council's online register shows what has been proposed on your street and how each one went, and a quick search there will tell you more about your chances than any brochure.
The ground needs as much thought as the planners. Every part of Ham is in class 3 on the British Geological Survey's shrink-swell scale, which measures how much clay soils swell when wet and shrink when dry. For an extension that means deeper foundations, a structural engineer's view on nearby trees, and a building control officer who will want to see the calculations. It adds cost and time, but it is a well-understood problem. The clay ignores conservation areas and moves under every house in Ham alike.
Ten listed buildings in the area are on Historic England's Heritage at Risk register. Those are buildings in poor condition, where repairs may attract grant money and will certainly attract scrutiny. They are not a hazard to the buyer of an ordinary house down the road, though anyone buying one of the ten should expect English Heritage-grade conversations about mortar.
In practice, the permitted development rights that let homeowners elsewhere build modest extensions without applying are thinner in Ham. In a conservation area or on a listed building, assume an application will be needed and ask the council to confirm in writing. Unlisted houses outside the conservation areas have more freedom, but the clay still has to be engineered for.
Extending a house in Ham is hard. Expect to apply for consent, wait for the answer and pay an engineer before you build anything.