Usually yes, unless your house is older than the planning system. Most homes here aren't listed. The neighbours put in planning applications at a steady clip. The oldest frontages come with a rulebook attached. How much you can build depends less on ambition than on whose permission you need first.
Tenterden has 164 listed buildings. One is Grade I, 13 are Grade II* and 150 are Grade II. Listing covers the whole building, inside and out, so knocking through a wall, changing windows or adding a rear extension to a listed home needs listed building consent on top of any planning permission. Doing the work without it is a criminal offence, not a paperwork slip. Grade II is the everyday tier and still binding. Grade II* and Grade I are where the conversations with conservation officers get long and detailed. The mapping behind this page records no conservation area inside the boundary it uses, so check with the borough council before you rely on that.
The neighbours are hardly frozen in aspic. The planning register records 1,655 applications between April 2024 and June 2026, and 714 in the last twelve months of that window. That tells you people here do add rooms, swap windows, fell trees and convert garages, and that the planning system is used to hearing from them. It tells you nothing about who got a yes. The number of applications is a measure of how many people asked, not how many got permission.
Away from the listed stock, the practical position is ordinary. Many modest rear extensions, loft conversions and outbuildings on unlisted houses can go ahead under permitted development, the national allowance that lets householders build within set size limits without a full application. A listed building gets none of that freedom. The slice of the area inside the High Weald Area of Outstanding Natural Beauty also carries tighter controls than an ordinary street. Before you buy on the strength of "scope to extend", ask two questions. Is the house listed, and does it sit inside any designated area? If the listing particulars go quiet on both, ask the council, not the agent. An agent's "scope to extend" is a sales line, and the council's answer is the only one that counts.
Most houses in Tenterden can be extended with the usual permissions, and a minority come under much stricter rules. Your freedom here is middling, and it depends almost entirely on which house you buy.