"PVR" wrote in message

1). If the joists are currently unprotected why is it necessary to use
5/8" drywall for the ceilings in the finished areas?

Makes you wonder about that. I'd use 1/2" because it is easier to handle
and is still much better that having nothing. Thinner is just too flimsy
though, IMO.


2). If I use ceiling tiles supported by plastic extrusions, the plastic
would melt in a fire. How can the drop ceiling be a satisfactory
alternative to a 5/8" drywall ceiling?

Some plastics can take high heat. While it is not banned from use, I doubt
it makes a barrier according to fire codes though.


I prefer the drop ceiling because there are several electrical junction
boxes attached to the joists and I assume reasonable access to these
should be provided.

Yes, it is against code to put permanent coverings over them. Dropped
ceilings make a lot of sense because in the future you may want to add
wiring, plumbing, who knows what.