Originally Posted by thekctermite
Treated lumber furring strips can be nailed to the top of the floor joists before you lay down the plywood. Cut them on a tablesaw out of 2x4, 2x6, or whatever is cheapest. Problem solved.
Now, plywood? Outdoors? It will not hold up. Even treated plywood doesn't last outdoors, it isn't designed for it. The wood may not rot if you use treated plywood, but it will certainly delaminate. At the very least, a good bitumenous rubberized membrane of some sort (or even rolled roofing) is in order underneath the decking to make the carport a little more water resistant.
Thanks for the suggestion. No table saw, so it'll be a challenge cutting these with my circular saw, but I think I can manage it.
As for plywood outdoors, it'll be coated with a polyurethane system designed for just such an application:
The result is a walk-on waterproof surface. In fact, several of my neighbors have used this (or similar) systems with great success. Btw, it rains a lot around here in the winter (N. California, in the redwood forest), so I don't think it's any fluke that these have held up well over many years.