I'm trying to build a deck where I can use the few feet under it as storage space.
I'm thinking of using 8mil (or 10mil, if nessacary) plastic sheet or vinyl sheet between the joists and the decking. Edit: 20" wide Aluminum flashing is also an option
The plastic or aluminum sheets would have to be cut in a way that one side is wider than the other, so when secured to the parallel joists, it would form a gradual slope of excess material.
I would custom bend some aluminum flashing at 90 degrees that would drain directly onto the plastic from under the siding. Vertically, where this deck attaches to the house would be at the last two runs of the siding, and the bottom of the ledger would be lined up with the top of the concrete foundation. The concrete is about 4 feet above ground, I shouldn't need any further drainage below the deck
I would either use an oversized rim joist with a gutter at the end to catch the runoff, or place a beam in a place where I can put a gutter on it.
Question 1: Does this setup seem sane, safe, and effective?
Question 2: I would prefer to use cedar decking, but I'm not sure if the wood on plastic would trap water and cause rot issues. Can I use real wood here, or must I use composite?
Question 3: What would maintenance be like for this system? Would there be potential ice issues in the winter?
Question 4: Would I be better off sandwiching the plastic between the joists and a layer of PT 1x2 instead of between the decking and joist?