How should I store between 30 and 50 sheets of QuietRock ES?
Use the garage if you're worried about the floor's capacity. Place the drywall blocks on the floor first (the truck delivering the drywall usually has a bunch of these to protect the drywall and to make it easier to get the lift under the stack). On top of the blocks, put some plastic if you're worried about moisture in the floor. The drywall goes on top of this, so it's off of the ground. And on top of the drywall, you can put more plastic or tarp if the garage isn't weather proof.