Yes, but you are building on the most heavily protected archaeology in Britain and the paperwork knows it. The town has a conservation area over its historic core. It has dozens of listed buildings. It has scheduled monuments scattered across the surrounding fields in numbers that would embarrass a county. Most ordinary houses here are entirely straightforward to extend. The trouble is that "most" is doing quite a lot of work in that sentence.
Historic England's register carries 68 listed buildings across the area, of which two are grade one, four are grade two star and 62 are grade two. If you buy one of them, the rules change completely: listed building consent is needed for alterations that affect the building's character, inside as well as out, and that catches windows, internal walls, chimneys, and often things a normal owner would call maintenance. Consent runs alongside planning permission rather than instead of it, and doing the work without it is a criminal offence rather than a civil one. The number is small against the town's total housing stock, which is the reassuring part, but it is not zero and the grade one and two star buildings in particular are effectively frozen.
There is one conservation area, covering Amesbury itself. Inside it, the ordinary permitted development freedoms are narrowed rather than removed: alterations that would be automatic elsewhere can need consent, demolition is controlled, and trees carry protection they would not have on the next street. Some conservation areas also carry directions removing permitted development rights entirely for things like windows and front elevations, so the specific direction covering your address is worth reading before you commission drawings.
Then there are the scheduled monuments, and this is where Amesbury stops being a normal Wiltshire town. The area's bounding box contains 21 of them. Scheduled monument consent is the strictest protection in the English system, administered nationally rather than by the council, and it applies to ground disturbance as much as to building. For most buyers this is irrelevant, because the monuments sit in the surrounding downland rather than in back gardens. For anyone on the edge of town near open ground, it is the first thing to check, because archaeology does not care that you only wanted a garage.
Against all that, people plainly do build here. Wiltshire Council's planning register records 509 applications across the area between April 2024 and June 2026, 238 of them in the last twelve months. That is a steady flow rather than a trickle, and it is the most useful evidence available that extending a house in Amesbury is a normal thing that normal people do rather than a heroic act of persistence.
The practical position is this. A post-war or later house on an ordinary estate street, outside the conservation area and away from a scheduled monument, is likely to sit under the usual permitted development rules for a rear extension or a loft conversion, subject to the standard limits and to whether previous owners have already used the allowance up. Anything in the historic core, anything listed, and anything on ground that has not been dug since the Bronze Age is a full application with specialist input. Find out which of those your address is before you make an offer, not after.
On freedom to alter a home, this is Amesbury's weak spot. The town sits in a landscape where the ground itself has legal standing, and while most houses escape the worst of it, the ones that do not are constrained about as tightly as English law allows.