Originally Posted by dexterdog
There are ceiling joists that I could hang the grid from, but the roof is a strange shape and I am not sure if I could do it easily. What size lumber should I use for the grid if I was going to hang it from the joists? Are 2x6's okay? I was thinking of running the beams across the top of the garage walls and connecting them in the center beam but that might not be the best route?
If you're allowed to suspend the grid from the ceiling with wires you could probably use 1x2s, depending on how many wires you use.
20x22x1.7 = ~750# for the drywall.
A single iron coat hanger wire can support 180#. For a safety factor of 15, you'd need 15x750/180 = ~60 wires.
Lay out how you want your 14 sheets of drywall to sit. Then comes how many wires of what tensile strength, then comes what size & type of wood for the sag.
The good part is you can test a prototype: one sheet of drywall, a 4'x8' wood rectangle and four hanger wires. If all is in order, you duplicate it 13x.
Post some drawings and photos.