I live in a townhouse (about 40 years old) and my neighbors recently had a piece of drywall fall from their attic roof and create a hole in their upstairs bedroom ceiling.
I examined my attic which is really just a crawlspace and on both ends there is drywall shimmed against the attic ceiling, about 3 rafter sections on each end have this drywall. There is about 20' in the middle with no drywall. It is not nailed or held in place by anything except smaller pieces of drywall about 3" by 3" that are nailed to the rafters. The drywall against the ceiling rests on these smaller pieces. About 25% of the drywall has sagged and has fallen down onto insulation (luckily it hasn't punctured my upstairs roof).
Why would a builder do this?