I was just patching a hole in the ceiling where a fixture used to be. The drywall is very weak. For example I put some furring behind the hole, mounted to the drywall. When I began to attach the patch to the furring, the drywall screws holding the furring pulled right through the drywall. The pressure I applied to drive the screw was enough to easily pull the furring loose.
I'm wondering what this means. Does old drywall become weak and crumbly? Is this water damage? Inferior product? Is the ceiling going to drop on me if I don't replace it?
If it is water damage, is there any good way to find the extent of it? I mean, I hate to poke holes all over the ceiling, but how else can I tell?
Btw, the roof was replaced a couple years before I bought the house. I don't think it's leaking now, but it may have been a few years ago.