I've just gotten a home from the early 1900s in Philly, and I'm working on plaster patching. I've noticed with close inspection that the dining room ceiling (a 10-footer) is fairly loose in many places, beneath the finish coat and paint, which is still pretty much intact, but with noticable parallel stress lines all the way across (I assume these lines correspond with lath strips, since they're perpendicular to the 2nd floor joists above).
I've read that a viable option for repairing this condition is to put new blue board and veneer plaster over the old ceiling. The sources I've looked at specify to attach 1x3 furring strips to the joists, through the existing plaster and lath. I'm wondering wether those furring strips are absolutely necessary, if I can locate and mark the joist locations and then use long drywall screws to attach the blue board directly to the joists. Also, should I be worried about the old plaster coming loose and adding weight stress to the new board?
I also wonder whether there's any other solution to this problem. The ceiling isn't falling apart, but I've managed to poke a considerable hole in one place just using my thumb and moderate pressure, and the old base coat looks like it's crumbling. I figure that stripping the paint, applying a bonder and then some veneer plaster could make the ceiling look better, but that this might just add stress to the crumbling base and precipitate more problems. Still, I'd like a professional opinion on that. I'm just dreading the prospect of hoising 4x8 sheets of blue board 10 feet in the air. Note that I can't access the joists from above, since they're beneath a finished 2nd floor.
Finally, if I do use blue board, I know it should be 5/8" instead of 1/2", but does it also have to be of the type specifically manufactured for ceilings, or can it be a standard grade as long as it's screwed into the joists on an acceptable schedule?