Sanded plywood is usually BC or AC fir, depending on the quality of the sanded side. I don’t believe they sand CFC at all. And, when using plywood, you gotta make sure that you are buying at least 5 ply, the 3 ply 3/8” and 1/2” is no better than junk. They used to use the 3 ply 1/2” on roofs, but it delaminates as soon as moisture got near it, and caused waves and buckles in the roof.
