Received a call to inspect an occupied 40 year old home to investigate why the bathroom ceiling collapsed. As soon as I walked inside, I noticed the drywall ceilings (entire home, both floors) were dropping at the center of each 4x8 sheet. In the attic, I discovered the drywall was only glued from seam to seam!! The glue gave way over time. Only nailed along the length of the drywall sheets. Measured the gap between joist and drywall at over 1". Informed the occupants that the ceiling could collapse at any time with potential serious personal safety consequences. The collapsed ceiling was wet from the 2nd floor bathroom and a leaking drain, but there were no nails in the joists or drywall. Amazing.