I am in the process of installing a metal roof over an outside deck. My rafters are in place and now I am getting ready to purchase and install my flashing and sheathing. I was planning on putting plywood over the rafters and cross (strapping?) the rafters with 2"x4" every 16" to secure the metal roof to. In reading the LogHome posts, it seems wise to install a vapor barrier over the plywood to prevent condensation from getting adsorb into the plywood from the steel roof. Am I on the right track here? Any suggestions or ideas are greatly appreciated.