We are going to make some "improvements" to our screened porch. The flooring of the porch was originally just a deck, made with 5/8" x 6" pressure treated pine. When the previous converted the deck to a covered screened-in porch, they covered the deck boards with plywood (3/4" sheathing). They thoroughly attached the plywood to the deck boards with exterior drywall type screws...probably over-did it...and caulked all the edges. They then glued down a green "astroturf" type polypropylene (?) carpeting over the plywood. Despite getting some weather coming in near the edges of the porch, the plywood is still very sound...no signs of rot. We have removed the astroturf and there is some glue residue left on the plywood. I was going to rip up the plywood and put down (perpendicular to the decking) either new PT decking or T&G pine on top of the old stuff...either of these would be painted with porch paint. Yesterday, I was in my local big box home improvement store and there is a cement-based siding product made by James Hardie that caught my eye. It's relatively thin (about 1/4"), but started to wonder about its possible use for flooring. If I left the plywood in place, sanded it down to remove the glue residue, and then laid the siding product over the plywood, setting it in some outdoor rated thinset mortar, would it last or even be worth the effort? I'm sure this type of use does not fall into what the James Hardie Corp would recommend or even consider a valid use for their product, but it certainly seems workable. What do ya'll think? Any opinions or similar applications would be appreciated.