"Edwin Pawlowski" wrote in message
t...

"Eigenvector" wrote in message
...
If I have ceiling joists that are 48" apart, will 5/8" drywall sag if
mounted on it?

Yes, it will look like crap


I'm not seeing too much information about that around, even though I'm
pretty sure 48" is pretty standard framing for a basement.

No, it is not

I see this in a lot of houses where I live, especially in downstairs
garages.

The roof joists are all 24".


I made the mistake of putting 1/2" up the first time - bad bad mistake
that cost me dearly. But 5/8" isn't that much more. The idea of
installing 2x4's between the studs isn't my idea of a fun time,
especially since it will introduce more margins for error unless I'm a
demon for measurements.

One method looks like crap and you have verified that. The other method
is correct. Your choice, do it right or a second half assed job. You
can get away with 2 x 3.




I am also considering the idea of using plywood backing over the joists
as a way to give the drywall a larger surface to attach to - even if it
isn't structural it will still remove any sagging. But that option has
the detraction of reducing my headroom by 1/4" or more. I know it
doesn't sound like a lot, but it all adds up - not to mention it will
make adding lighting fixtures a huge pain in the ass since you can't cut
plywood with a drywall saw.

That certainly narrow down the options. 1/4 plywood is not going to help
much anyway. That too may sag at 48" spans. That gravity thing is not
going away.
That sucks. That adds a hell of a lot more work that has to be done.

Attaching the studs to the existing joists itself is going to be a trick

Nothing for it then but to do it right.