When it comes to interior work I find it always best to work from the top to the bottom. This way, what ever mess you make working on the cabin roof won’t ruin any work you’ve done below it. You’ll still need to sheet out, if your using epoxy or glassing above head, especially if you don’t intend on replacing the cabin floor.
When I first enterd the yacht I noticed the interior fibreglass inner roof was showing. Mouldy and covered in graffiti, someone must have broken into her and gone buck wild with a spray can.
My first job would be to insulate the roof. Using a sheet of plywood I cut battens that would be epoxy fillited yo the roof.
The roof had previous been carpeted, which meant all or my insulation work would need areas to sit in.
Using temperature resistant contact adehsive I went about gluing closed cell camping mats to the cabin roof. The camping mats were already sandwiched between aluminium and cost a total of £50 for 9 mats. I would also add my own layers of double sided aluminium bubble insulation. This would be good enough. I I’m limited on room, as anything over 30 mm I would not be able to stand up.