wall demo and patch
Yes, use whatever is necessary to level the surface. It is probably lath and plaster. You will have to fill more than a one layer of 1/2" sheetrock. You can use multiply layers of sheetrock, or plywood first with sheetrock over it ( sheetrock and plywood comes in many different thickness). Its best to have the patched surface flush with the ceiling or a little indented, You definitely don't want to start with a hump, where the patch sticks out past the existing surface.
Usually from my experience, the plaster in a house that old will start deteriorating(cracking) and once it starts it just keeps going. If you have the funds, it would be a good time to go over all of the old plaster with a layer of sheetrock. That might be to costly, but it would be a good time to do a complete remodel on the walls and ceiling.
Sand with a heavy grit sandpaper (60 or 80), and clean surface so new mud will stick to the paint. I use taping mud(mixed loose) and paper tape over the seams and cracks (if gaps, prefill and let dry before taping). Then finish mud, running passes on each side of the joint leaving a line in the center with an 8" knife, always feather the edge. Let dry, and look for air pockets to be scraped with a knife and then a tight pass of mud to fill them(let dry) and sand. Then apply another coat of mud with a 12" knife, Passing each side of joint, feathering the edge. Let dry and sand.
The ridges that might be left from trying to feather the edge must be wiped away with a damp cloth.
Last edited by redmanblackdog; 01-11-2011 at 01:44 PM.