Hello-

I have a contractor building a porch to the house, it will be raised off ground from 6"(next to house) to 20" (porch outer wall) setting on Big Foot concrete filled pillars. Floor joists 2x12, 16" OC. 2x6 outer walls. I want to install 3/4" solid prefinished hardwood flooring either 2.25 or 3" width at variable lengths.

The contractor wants to lay 1/2" 4x8 plywood on top of joists then 2(stacked & glued together) - 4x8x2" foam (closed cell, non compressible) blue board for a total of 4" depth @ R value of 10. Then on top of the blue board, 3/4" tongue & groove plywood. Total subfloor depth is a sandwiched 5.25". Is this acceptable for a hardwood floor subfloor? The blue board is said to act as a vapor barrier also. I will have a layer of 4mil poly & recommended under layment under the hardwood flooring installation, question is, is the blue board O.K here?

Let me restate the order here: The floor will be nailed down 3/4" solid prefinished. So, from the top down in order it will be: 1) 3/4" hardwood. 2) manufacturer recommended under layment. 3) 4 mil poly vapor barrier. 4) 3/4" tongue & groove plywood. 5) 2" blue board. 6) 2" blue board glued to #5 above. 6) 1/2" plywood.7) all above resting on top of 2x12's on 16" centers.

Thanks, Robes-