Our company currently uses orientedstrand board (OSB) for both subflooring and roof sheathing. Previously we used 3/4-inch pine plywood on floors and 3/8-inch pine plywood on roofs (fir plywood costs too much for our budget). The switch to OSB saves us money – almost $1 a sheet – but we made the switch primarily because we think that OSB is a better product. In this case, we're getting better quality and a lower price. We think OSB makes a stiffer floor, so we figure it also makes a stiffer roof. Just be careful when you buy your OSB that you're getting rated orientedstrand board (see "An OSB Primer," facing page). Spans and Specs For flooring, we use 23/32-inch tongue-and-groove OSB,
