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Metal Q deck -to-Wood Contact

Jack Smith | Posted in General Questions on

Hi all! I have a concrete porch above a storage room. The old joists that support the porch used to sit on top of a block foundation also touching the backs of the brick veneer adhered to the outside face of that foundation wall. the parts in contact with the masonry rotted out (it was also insulated with fiberglass and drywalled, effectively keeping it wet for a while), dropping the cement porch and q deck about 1” before it was noticed and temporarily shored up.  I need to swap the whole structural system. installing a capillary break and separating the joist form wicking moisture I have a good plan for. question is how I can put new joists and plywood under the q deck and keep the plywood waterproof while working inside out? I’m worried mainly about condensation.  Should I use something like a zip system which would give me more moisture control then regular plywood and I can leave the bottoms uninsulated? in theory the grooves of the q deck mean its not 100% metal to wood contact. or I can apply a spray flashing type product or rubber roof to the bottom of the q deck to protect the plywood but I’m lost. to be clear the waterproofing on top of the metal deck is intact and the concrete does not leak. i don’t want to redo the porch top since it ties into so many different things. thank you so much, i know its long

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