by Dirtman » Tue Feb 14, 2006 2:19 pm
For a fairly solid floor on joists 16" OC (on center), 5 sheets of 4 x 8 BC plywood (5/8" minimum, 3/4" preferred). You'll have plywood left over. Use glue and screws, not nails, to put it down or you may get squeaks when you walk on it.
If you'll be putting ceramic tile on it, you'll want two layers of 5/8" or 3/4" plywood. Again, 3/4" is preferred. The first layer can be CD, the top layer needs to be BC.
CD is rough on both sides, BC is rough on one side, smooth on the other.
If you've never done this, hire a professional. :D