Yes, and people do it constantly, unless the building answers to Historic England rather than to you. There are 264 listed buildings in the area. A scheduled monument sits inside the same boundary. Hundreds of planning applications have gone in over the past couple of years. Altering a house here is entirely normal. Doing it without asking first is a short route to an enforcement notice and a very expensive lesson in lime mortar.
Historic England's register carries 264 listed buildings in this area: 7 at grade one, 8 at grade two star, and 249 at grade two. That last number does most of the work, and it is the one people underestimate, because grade two is routinely treated as listing-lite by buyers who then discover it is nothing of the sort. Listing covers the whole building, inside as well as out, along with later additions and often structures within its grounds. Consent is required for anything affecting its character, which in practice means internal walls, staircases, fireplaces and joinery as readily as it means the extension you sketched on the back of the viewing brochure. Replacing a rotten timber window with something double-glazed and sensible is the classic point at which an owner meets the system properly for the first time.
There is also 1 scheduled monument within the area, which sits at the strictest protection tier of all. That matters mainly for anyone whose land runs up against it, because works affecting a scheduled monument need consent from central government rather than the council, and the process is not designed around your builder's availability in March.
None of this stops people altering their homes. The planning record for this area carries 595 applications between April 2024 and June 2026, with 241 of those lodged in the last twelve months. Whatever else the constraints do, they have not produced a town where nobody bothers. They have produced a town where everybody employs an architect who knows the drill.
One listed building in the area appears on Historic England's Heritage at Risk register, which identifies buildings in poor condition rather than dangerous ones. For most buyers this is background rather than a warning. For anyone contemplating buying it, the register cuts both ways: repair works may attract grant support, and they will certainly attract close attention from the conservation officer.
Practically, the rules of thumb that apply elsewhere do not survive contact with this town. Permitted development rights, the changes an ordinary homeowner can make without applying, are curtailed on listed buildings and trimmed in designated landscapes, and roughly 72% of this area sits within the South Devon National Landscape. Anyone buying with a loft conversion in mind should establish the property's listing status and the constraints attached to its address before exchange, not after. South Hams District Council is the authority that decides, and a pre-application conversation costs a fraction of a refused scheme.
Freedom to alter a home here is limited, and the limitation is the reason the place looks the way it does. The medieval lanes and Elizabethan frontages that sold you the town are protected precisely so that nobody, including you, can improve them.