Plaster in finished attic replaced with insulation and drywall
Hello, all. I just bought an 1857 Gothic Revival fixer-upper in northern New Jersey. The attic is a finished accessory apartment consisting of several rooms plus a kitchenette and bath.
A few years ago the previous owners tore out a lot of the plaster ceilings and walls in the attic and replaced them with insulation and drywall. (This is directly against the roof and exterior walls, as opposed to insulating the floor of the attic.) The remaining plaster has a lot of cracking, possibly due to the three layers of shingles on the roof weighing down on it, but the drywall is also having problems, especially that all of the tape is coming loose and peeling off. I don't think it's due to shifting of the house, because I'm not seeing much cracking on the walls of the main floor.
I have been reading in other threads that attics and roofs need to be allowed to breathe or else problems may develop with humidity build-up and other issues. I am starting to wonder if installing the insulation and drywall was a big mistake that has upset the ecosystem of my house and is causing these problems. If that is the case, what the heck do I do? Remove the insulation? Who would be the best person to consult with? A roofer? A plaster restorer? An engineer?