Okay, I made a previous post about this and have determined my original plan is no bueno. For light backstory, I've got a 3 car detached garage 40' x 25' with rafters every 4'OC (pictured below). I've been told I can't just hang drywall and insulation on them because of the fear they cannot hold the weight and will bow. I contacted the builder and they do not have LL/DL specs for the build since it was built in 2000.
My newest crazy plan is to install support beams in the center of the rafters that run to the cement garage floor. It would be a bit unconventional because there would be a support pole in the middle of the room every 4 feet, but we think that we will be able to make it work.
If I did this, the plan is to run 2x4 perpendicular to the rafters 16" OC and then hang 1/2" lite drywall and R-30 insulation above that. I've done the weight calculations and it would be adding 2.7 lbs/sqft not counting drywall mud.
Do ya'll think this will work?