Yes, and with markedly less paperwork than most of this coastline demands. The town has thirteen listed buildings in total. It has one conservation area. Applications to alter homes go in by the hundred. Whatever stops your extension here, it is unlikely to be the heritage file, and considerably more likely to be what the ground does in a dry summer.
Historic England's register lists 13 listed buildings across the area, every one of them at Grade II, with nothing at Grade I and nothing at Grade II star. Thirteen is a small number for a town of this size, and it means the chance of a buyer landing on one is slim. If you do land on one, the rules bite properly: listed building consent is needed for alterations affecting its character, that applies inside as well as out, and it sits alongside planning permission rather than replacing it. Owners who treat a Grade II listing as a decorative detail on the sales particulars find out otherwise at the point they want new windows.
There is one conservation area in the town, at Old Milton Green. Inside a conservation area boundary the ordinary freedoms narrow: demolition, work to trees and the more visible external alterations come under closer control, and some of what would elsewhere be permitted development needs an application instead. The line on the map is what matters rather than the general vicinity, so an address a street away from the green is worth checking properly rather than assuming. Boundaries in these places rarely follow the logic a buyer expects.
The evidence that people do alter homes here is not theoretical. Planning records carry 389 applications across the area between April 2024 and July 2026, with 165 of those in the last twelve months. That is a town where somebody on your road is currently arguing with a builder about a rear extension, and the planning system is processing that argument at a steady clip.
The genuine constraint is underneath the house rather than in the filing cabinet. The British Geological Survey's ground stability mapping puts shrink-swell potential at class 3 on its scale across the whole of the area, meaning ground that changes volume with moisture as clay does through wet winters and dry summers. Practically, that shapes foundation depth for an extension, makes nearby trees a real design question rather than a landscaping one, and is the reason a structural engineer's involvement is money rather than ceremony. Every other ground hazard the survey maps here, from landslide to soluble rock to running sand, sits at the lowest class, so this is one specific issue rather than a difficult site in general.
For most owners the practical position is straightforward. The great majority of homes in New Milton are unlisted and outside the conservation area boundary, which puts a rear extension or a loft conversion into the ordinary permitted development conversation, subject to the usual national limits on size, height and how close you build to a boundary. A lawful development certificate remains the cheap insurance for anyone planning to sell later, because a buyer's solicitor asking for paperwork you never obtained is a slower and more expensive problem than getting it at the time. Anyone inside the conservation area, or holding one of those thirteen listings, should assume a full application and budget the extra months.
Freedom to build on is one of the real strengths of buying here, particularly for anyone who has previously owned in a place where every window frame came with a consultation. Get the foundations designed for clay, and the rest of it is mostly a conversation about how much of the garden you are willing to give up.