You can extend a house in Devizes, as long as it isn't one of the old ones in the middle that everyone wanted in the first place. Hundreds of buildings are listed. Three conservation areas cover the town and its edge. Most of the ground is clay that moves. The neighbours still send in hundreds of planning applications a year. It can be done, but it takes more paperwork than you'd expect.
Devizes has 356 listed buildings. Six are Grade I, 43 are Grade II* and 307 are Grade II. Listing covers the whole building, inside and out, so changes that would be routine elsewhere, such as windows, internal walls or an extension at the back, need listed building consent on top of any planning permission. Working on a listed building without that consent is a criminal offence, not a matter of form. For a Georgian townhouse, the rear extension you pictured will be negotiated line by line with a conservation officer.
The area has three conservation areas: Devizes itself, the Devizes Victoria Road Quarter and Stert. Conservation-area status puts more control on anything visible from the street, and the council will expect new work to match the character around it. Some changes that need no application elsewhere can need one here. Buyers who assumed a post-war semi was exempt from any of this sometimes find out its front garden is in a conservation area.
There are also two scheduled monuments in the area, the strictest tier of heritage protection. They mainly matter to anyone whose land sits next to one, not to someone adding a kitchen.
People still get on with it. Wiltshire's planning records show 1,014 applications in the area between April 2024 and June 2026, and 439 in the last twelve months. Hundreds of households a year think their house is worth arguing over, which tells you owners here aren't put off by the process.
The ground matters as much as the planners. The British Geological Survey places about 83% of the area's postcodes in shrink-swell class 3, the highest class recorded here. That means clay that swells when wet and shrinks when dry. For an extension, it usually means deeper foundations and a structural engineer's view before the builder quotes, not a reason to panic. Budget for the foundations before you choose the bifold doors.
One listed building in the area is on Historic England's Heritage at Risk register. That means a building in poor condition whose repair may qualify for grant support and will be watched closely. It isn't a risk to someone buying an ordinary house down the road, and the owner of that building has bigger problems than yours.
In practice, much depends on which house it is. A modern home outside the conservation areas may be able to use permitted development rights for a modest extension or loft conversion. A listed house or one in a conservation area will usually need consent for work that elsewhere would go ahead without asking. Check the listing status and conservation-area boundary for the exact address before you offer, and get pre-application advice from the council before you pay an architect.
Freedom to alter a home is one of the town's weaker points. The historic core is closely controlled, and even the newer edges come with clay that has to be dealt with.