Yes, across most of Herne Bay, provided the ground under your house agrees. Listed buildings are few, and nearly all of them are at the lowest grade. Four conservation areas cover the parts people tend to photograph. The neighbours apply for planning permission all the time. The heritage officer is the smaller worry here, and the clay is the bigger one.
Herne Bay has 71 listed buildings: 70 at Grade II, 1 at Grade II*, and none at Grade I. If you buy one of them, listed building consent comes into almost any change, inside as well as out, from windows to internal walls, and "we only replaced the doors" isn't a defence anyone has had much luck with. If you buy one of the other homes in town, the listing register is unlikely to trouble you at all.
Four conservation areas fall in and around the town: Herne Bay itself, Eddington, Broomfield, and Under the Wood at Chislet. Inside them, changes to a building's appearance get more scrutiny, and work that would go ahead without an application elsewhere can need planning permission first. Buyers of a period frontage in the seafront conservation area should expect the council to have an opinion on the replacement windows.
The neighbours clearly aren't put off. There were 807 planning applications between April 2024 and June 2026, 350 of them in the last twelve months of that window. That's a town that can't leave its houses alone, which is the best evidence there is that altering a home here is normal rather than heroic.
The real constraint is underground. The British Geological Survey's shrink-swell hazard reaches class 3 in the area, and about 51% of the area is at that class or above. The town sits mainly on London Clay, which swells when wet and shrinks when dry, taking shallow foundations along with it. For an extension that means deeper foundations and a structural engineer's view before the builder quotes, not a reason to give up on the kitchen. Trees near the proposed footings deserve a mention in that conversation too.
One listed building in the area is on Historic England's Heritage at Risk register. That means a building in poor condition whose repair may qualify for grant support and will certainly get scrutiny. It's a concern for whoever owns it, not for the buyer of an ordinary house down the road.
In practice, most homes outside the conservation areas and off the listing register can take modest extensions under permitted development, the national rules that allow some work without a full application. Inside a conservation area, or on a listed building, assume you'll need consent and ask before you draw anything. Either way, the ground survey is worth paying for before the architect.
Your freedom to extend in Herne Bay is about average. The planning rules are light across most of the town and tighter in a few pockets, and the clay has its own requirements everywhere.