Yes, for most houses, but Ashford has more listed buildings than its post-war look suggests. There are hundreds of listed buildings across the area. The neighbours file well over a thousand planning applications a year. Part of the ground is clay that moves. A standard semi is straightforward to extend. The old buildings and the clay are where it gets slow and expensive.
The area has 348 listed buildings: 5 Grade I, 15 Grade II* and 328 Grade II. Listing covers the whole building, inside and out, not just the front the estate agent photographed. Changes that affect its character, including extensions, new windows and internal walls, need listed building consent on top of any planning permission. Grade II is the ordinary tier and still needs consent. Grade II* and Grade I are rarer and much harder to change, and the rules apply to a homeowner who wants a utility room just as much as to a cathedral. Buying a listed house and planning to find out about this later is a common mistake, and an expensive one.
There are 2 scheduled monuments in the area, the strictest tier of heritage protection. They mostly matter if your land borders one, where even digging a garden trench can need consent.
People here do change their homes, and often. Between April 2024 and June 2026 the planning record lists 2,849 applications, 1,250 of them in the last twelve months. That volume tells you nobody treats the town as a museum. It says nothing about how many were approved. It only shows that extending a house here is a normal thing to try.
The ground needs as much attention as the planning officer. The British Geological Survey's shrink-swell hazard reaches class 3 in parts of the area, and about 7% of it sits at class 3 or above. Shrink-swell clay swells when wet and shrinks when dry, and new foundations have to allow for it. In practice that can mean deeper footings, a structural engineer's report before the design is fixed, and extra care near large trees that draw water out of the soil. It isn't a reason to give up on an extension, but it is a reason not to take the cheapest quote for the footings.
For an unlisted house, many single-storey rear extensions, loft conversions and outbuildings can go ahead under permitted development rights, within size limits, with no full application needed. Flats don't get the same rights, and a listed building needs consent almost regardless. The sensible order is to check whether the property is listed, check the ground, and then ask the council whether your plans fall under permitted development before you commission any drawings. Knock the wall through first and ask later, and you could end up paying to put it back.
Your freedom to extend in Ashford is below average. Hundreds of listed buildings and patches of shifting clay mean that anyone buying for the extension needs to check the property and the ground before they commit.