Yes, in most of Old Basing, as long as the house isn't one of the old ones. Around seventy buildings are listed. There's a conservation area. The neighbours file planning applications at a rate of several a week. The rules bite where the old brick is, and relax where the post-war semis and bungalows begin.
The area holds 71 listed buildings: 2 are Grade I, none are Grade II*, and 69 are Grade II. Listing covers the whole building, inside and out, so on a listed home the replacement window, the knocked-through wall and the new kitchen extension all need listed building consent as well as any planning permission. Grade II is the most common tier and the least strict, but it still means asking before changing anything that affects the building's character. Buyers of a listed cottage are buying the house and the conversation with the council that comes with it.
There's one conservation area, Old Basing itself. Inside it, the council takes a closer interest in anything visible from the street, including extensions, demolition and some works to trees, and some changes that are automatic elsewhere need an application here. Owners inside the boundary should expect to justify how an extension looks, not only whether it fits on the plot.
The area also has 2 scheduled monuments, the strictest protection tier in the system. They include Basing House and the Grange Field. Unless your garden backs onto one, they're more likely to shape the view than your plans.
The planning register shows how busy people are anyway. From April 2024 to June 2026 there were 519 planning applications in the area, 205 of them in the last twelve months. Nobody in Old Basing is short of ideas for the side return. Those counts say nothing about how many were approved, only that altering a home here is normal rather than exceptional.
In practice, most homes in Old Basing are not listed and sit outside the tightest controls, so the usual permitted development rights for modest rear extensions, loft work and outbuildings are the starting point. Those rights shrink inside the conservation area and don't apply to listed building consent at all. Before buying with an extension in mind, check whether the house is listed, whether it sits inside the conservation area boundary, and what the council's planning register holds for the street. A ten-minute search now saves a refused application later.
Freedom to extend here is middling: easy enough on an ordinary post-war house, slow and closely watched on anything old or inside the conservation area. Buy the plot for the extension, and check the listing before the architect.