Can 1/2" drywall be applied to a 2 foot O/C floor joist system, without sag appearing??

T.J.I. - Top and bottom 1 1/2" laminate ply with OSB between.


Or do I have to use 1/2" strapping to 16" or 12" O/C, or go to 5/8 firerated drywall??

Can 1/2" drywall be applied to a 2 foot O/C floor joist system, without sag appearing??
Yes. But ad this step for a better finish. Install 1X4s perpendicular to the joist with nails on 16 inch centers. Then run a string from one side to the other to check for dips and bows in the ceiling. Tap the 1X4s to align them then install drywall. you'll have a perfectly flat ceiling with sufficient support.
Reply:why not run a 2 x 4 from beam to beam but level with the ceiling so you can then nail to the 2 x 4 in the middle. put the 2 inch side down not the 4 inch.
Reply:go 5/8 because 1/2 will definately sag
Reply:5/8 drywall is definitely the way to go, though you should probably block between your joists at the tapered seems of the drywall
Reply:sure, we use 1/2 inch all the time on truss ceilings that are 2 feet o/c. the old sheet rock from 20 years ago did sag, but not anymore