Fastening 3/4-in. Plywood Sheathing
I’m working on a house where the architect has specified 3/4″ plywood for the exterior sheathing. I talked to him and he offered two reasons. First, it’s a high-end custom home, it has lots of nice soundproofing features like 5/8″ drywall and cork underlayment under the floors, he feels it will give the house a more solid feel. But more important, there is 2″ of continuous exterior insulation, then furring strips and either shiplap or shingle siding. He’s worried that with the length of the nails needed to go through the furring and the insulation that regular 1/2″ sheathing isn’t going to have enough holding power.
My thought is just to make sure the nails go into the studs. Unless we go with fasteners beyond what a nailgun can shoot we’re limited to 3-1/2″ anyway which wouldn’t fully penetrate 3/4″ , my understanding is nails grip best when they penetrate sheathing. And with 3/4″ plywood topping $75 a sheet these days it’s a significant upcharge. There is a structural engineer involved and his section says “minimum 1/2″ sheathing” so there’s no permit issue with ignoring the architect.
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