Almost certainly, and with less argument than most of Cornwall. Sixteen listed buildings in the whole area, and none of them are in the top tiers. No conservation area at all. One scheduled monument. Neighbours have been putting in planning applications at a steady clip. The thing most likely to complicate your extension here is not a heritage officer, it is what is under the garden.
Historic England's register lists 16 listed buildings across the area, all of them grade two, with none at grade one and none at grade two star. Listing is a property-by-property protection rather than an area one: if your house is on that list, almost any alteration affecting its character needs listed building consent, and that includes work a normal house would do under permitted development, down to windows and internal layout. If it is not on the list, and 16 buildings across a town means the odds are it is not, listing is somebody else's problem.
One scheduled monument sits within the area. That is the strictest tier of protection in the system and it applies to the monument and its setting rather than to housing generally, so it matters only if you happen to be buying land beside it. Worth checking on a specific address, irrelevant almost everywhere else.
The more useful evidence is what people here actually get on and do. The planning register records 187 applications across the area between April 2024 and June 2026, of which 85 landed in the last twelve months. That is a town where altering a house is routine rather than exceptional, and where your architect will have done something similar down the road recently enough to remember it.
The ground is the genuine complication. The British Geological Survey's mining data covers every postcode in the area, with an average of about 18 recorded abandoned workings within 500 metres and up to 22 around the worst-affected postcodes. 123 of the area's 124 postcodes sit directly over a recorded working. In practical terms that means a mining search on purchase, quite possibly a specialist report before you build anything substantial, and a lender or insurer who may want to see one before they commit. It does not mean your house is about to fall over, and nobody should read it that way. It means the paperwork here has an extra chapter, and that the cost of a rear extension may include a ground investigation that a buyer in a non-mining county would never think to budget for.
So the shape of it is this. Most homes here are free to use normal permitted development rights for the usual rear extension, loft conversion or outbuilding, subject to the same size and siting limits that apply anywhere. The exceptions are the listed handful, anything in the setting of the scheduled monument, and any work that the mining legacy pushes into needing a foundations design rather than a standard trench. None of those are hypotheticals a solicitor will miss if you ask the question early.
Freedom to alter a home is one of Perranporth's quieter advantages: light heritage constraint, an active local planning register, and no conservation area drawing lines down the middle of streets. Budget for the mining search rather than the appeal.