Yes, in most of Bovingdon, though the old core comes with conditions. The village has a few dozen listed buildings and one conservation area. Most homes are post-war and carry neither label. Neighbours lodge plans constantly. The answer depends on which side of the historic boundary the house falls.
Historic England lists 40 buildings in and around Bovingdon: none at Grade I, two at Grade II* and 38 at Grade II. Listing covers the whole building, inside and out, so even a new internal doorway or a replacement window in one of them needs listed building consent from the council on top of any planning permission. Forty is enough to give the old village a character and few enough that most buyers will never own one.
There is one conservation area, Bovingdon's own, covering the historic centre around the church. Inside it, the council takes a closer interest in anything visible from the street, from extensions and dormers to demolition and some tree work, and changes that would pass without comment on the post-war estates can need a full application. The single most useful check is Dacorum's conservation area map, to see whether the house sits inside that line or outside it, since that one fact decides how much paperwork follows.
Plenty of people are trying anyway. The planning register logged 919 applications for the area between April 2024 and June 2026, 417 of them in the last twelve months. That is a neighbourhood that extends, converts and reroofs as a matter of routine, and whatever loft or kitchen idea a buyer arrives with, Dacorum's planners have very probably read it already.
For the ordinary semi or detached house outside the conservation area and not listed, many modest rear extensions and loft conversions can fall under permitted development, the national rights that let householders build within set limits without a full application. Inside the conservation area, or on a listed building, those rights shrink or vanish. Either way, a lawful development certificate from the council is cheap insurance for anyone who plans to build without a full application, because a builder's view on what counts as permitted carries no weight at all.
Freedom to extend in Bovingdon is middling: easy enough on the post-war streets that make up most of the village, and a slow conversation with the council for anyone who buys into its oldest corner.