Will R-70 cellulose sag ceiling drywall 24″ o.c.?
My plans call for an R-70 ceiling of loose-pack cellulose in double-netted bays between trusses 24″ o.c., with 5/8″ Type X drywall holding it up as my air barrier. My installer says this will weigh about 2.55 lbs/sq/ft. Is this too much? Will it sag over time or pop screws? Do I need to use some special (expensive) low-sag drywall? I don’t want to go to the expense and lost clearance of, e.g., an OSB layer above the drywall.
Anyone have experience with this?