Planning is not needed if only Velux windows are used and only to the back of the house. If ever selling, the attic room can't be called a room as in most cases, without dormers that do need planning permission, it wont meet the required floor to ceiling height over I think more than 50% of the floor area. But any buyer will see it for what it is particularly if it is done properly.
My attic is done for a while now but at the time I found ‘’prices from only’’ that you see advertised to be very misleading. They were usually for a very basic conversion. Maybe only 1 Velux window, maybe only 2 lights and 2 double sockets. Chipboard floor, proper t&g deal or hardwood floor extra. Basic plank stairs, to match existing stairs extra. Flooring in the eaves for storage extra. Proper insulation extra. Replacing existing tank in attic extra. Bathroom extra, where it is included, tiling is extra, that's off the top of my head, there are more.
Don't get anyone to do the job if an architect's certificate of compliance is not included in the price, apart from knowing the job is done properly, you will need it if selling in the future. I asked one cowboy who priced the job about a cert and he very kindly offered to take €250 off the quote once I paid, saying I could then get any Architect of my choice to do it
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