Usually yes, provided the house is not one of the old ones and not in the middle of the old bit. The town carries a lot of listed buildings for its size. The historic core sits inside a conservation area. Almost every postcode has old mine workings somewhere beneath or beside it. None of that stops work happening, and plenty of it does happen, but it does mean the answer depends more on which house you bought than on what you want to build.
There are 72 listed buildings in the area. None are grade one, 3 are grade two star and the remaining 69 are grade two. Listing applies to the whole building inside and out, not the pretty elevation facing the road, so on a listed property the internal doors, the staircase, the plaster and the windows are all in scope. Listed building consent is needed for alterations affecting character, it runs alongside any planning application rather than instead of it, and carrying out work without it is a criminal offence rather than a paperwork problem. Seventy-two is a high count for a town this size, which is a fair description of how much of Marazion is genuinely old.
One conservation area covers the historic centre. Inside it, the demolition of walls and outbuildings can need consent, tree work requires notice to the council, and the acceptable palette for windows, doors, roofing and render narrows considerably. Cornwall Council can also remove permitted development rights within a conservation area through a direction, so the sensible first move on any property inside the boundary is to ask the planning department what rights that specific address still holds rather than assuming the national defaults apply.
The live evidence says people do alter houses here. Planning records show 91 applications across the area between April 2024 and June 2026, with 43 of those in the most recent twelve months. That is a steady flow of householders getting extensions, garden rooms, roof alterations and window replacements through the system in a town of this size. The constraints shape what gets applied for. They have not stopped anyone applying.
The ground under the town is the other thing a builder will raise. Around 95% of postcodes are affected by recorded abandoned mine workings, with the nearest recorded working measured at zero metres in places, and 13 postcodes sit directly over one. This is old Cornish metal mining rather than coalfield, and it is not a prediction of anything happening to any particular house. What it means practically is that a mining search is standard here, a specialist report may be wanted on top of it, and both a lender and an insurer may ask questions before they commit. Foundations for a new extension are exactly the point at which that history becomes a live engineering question rather than a historical one.
The practical summary is that this is a two-tier town for alterations. A postwar or later house outside the conservation area, not listed, is a fairly normal proposition: permitted development rights broadly apply and a straightforward rear extension is a straightforward job. An older house inside the boundary, or a listed one anywhere, is a consent-led project where the design conversation starts with the conservation officer and the budget assumes specialist materials. The mining legacy applies to both.
Marazion sits in the middle on how freely you can alter a home: not a locked-down heritage museum, but not a blank sheet either, and the difference between an easy project and an expensive one here is decided before you exchange rather than after.