Deck being built.
We installed 3/4 inch spruce plywood over the 2x10 floor joists. The floor joists were installed with a 2 inch slope so that we obtained good drainage.
Applied roof membrane to the top of the plywood.
This method will make the area below totally waterproof. On top of this membrane we will install composite decking. Composite decking does not require refinishing which this south facing deck will require. I will install it on pressure treated sleepers which will allow space for water to run off the deck/roof.