Yes, you can extend a house in Teddington, but you will need patience, paperwork and a structural engineer. Listed buildings run into the dozens. Conservation areas cover much of the town and the land around it. The ground is clay that moves with the seasons. Plenty of people still build here; very few of them do it quickly.
Teddington has 82 listed buildings. None is Grade I, eight are Grade II, and the other 74 are Grade II. Listing covers the whole building, inside and out, so changing a listed home needs listed building consent from Richmond upon Thames on top of any planning permission, and Grade II brings closer scrutiny again. Even the most minor-looking jobs, such as replacing windows, moving an internal wall or changing a roof covering, can need consent. Doing that work without consent is a criminal offence, and the next buyer's solicitor will spot it.
Conservation areas cover far more homes than listing does. The search area around the town takes in 28 of them, including High Street Teddington, Teddington Lock and Normansfield. Inside one, the council expects any change to preserve or enhance the area's character, demolition needs consent, and some work that would go ahead without a planning application elsewhere needs one here. Ask the council's planning team which conservation area the house is in and whether any extra controls apply to that street. A side extension that would be unremarkable on a modern close can turn into a correspondence course on roof pitch three streets away.
There is one scheduled monument in and around Teddington, the strictest tier of protection there is. It only matters if your land runs up against it.
The neighbours are certainly trying. Richmond upon Thames logged 1,031 planning applications for the area between April 2024 and July 2026, 401 of them in the most recent twelve months. That is a town altering its homes steadily, one application at a time. The last big land grab here was the enclosure of Teddington's common land for Bushy Park in 1540, and that one went through without a single objection from the neighbours.
The ground has its own say. The British Geological Survey puts the whole of Teddington in shrink-swell class 3, so every part of the town sits on clay that swells when wet and shrinks when dry. For an extension, that means deeper foundations than sandy ground would need, extra care near large trees, and a structural engineer's view at the design stage, with an estimate that allows for it. Clay is common enough in this part of London, and no reason to give up on the plan. It does change the cost and design of anything new you build.
In practice, a house outside the conservation areas and off the listed register may get some rear and loft work through permitted development, the national rules that let modest changes go ahead without a planning application. Inside a conservation area those rights shrink, and on a listed building almost everything needs consent. Ask the council for a certificate of lawful development for any permitted development scheme before the builder starts, because a neighbour's planning knowledge is not a defence.
Teddington is one of the hardest places to extend a home: the protections are dense, the ground needs engineering, and anyone who wants to change their house should expect permission to take longer than the build.