My upper floor used to be a large attic. Sometime in the past the entire space was converted to living space: 2 bedrooms, 2 finished closets, and two unfinished storage "closets".
Much of the ceiling is built against the roof, and angles down towards the exterior walls. The walls and ceiling are all lathe and plaster. On the ceiling they simply nailed the lathes across the inside of the roofing members and then plastered over it. There is no insulation, and no barrier between the roof shingles and the interior lathe and plaster.
The roof is composition shingle, and doesn't have solid sheathing underneath.
I'm going to remodel the walls and ceiling this summer. I'll knock out the lathe and plaster and install drywall.
The roof will need to replaced within the next five years. It will require a full tear-off and installation of new plywood sheathing.
OK, enough background. Thanks for reading this far!
What is standard practice when building a ceiling against the roof?
How will I protect my new drywall ceiling from being damaged when the roof is torn off? Should I install plywood or OSB under (above) the drywall? Or maybe just put off the remodel until the new roof is in place?
I want to put insulation between the roof and the ceiling. Can this be done when replacing the ceiling, or would it be best to wait and have it put in when the new roof sheathing is installed?