To ensure that your deck is ready for vinyl decking it must meet certain criteria:
It should have a proper slope.
If it’s a 2x6 plank deck, it should be sheeted with 1/2” or 5/8” plywood with a good (smooth) side. Construction grade plywood with knot holes, O.S.B. Board, and pressure treated plywood don’t allow the vinyl to adhere correctly and won’t work.
Zinc coated decking screws should be used to install quality one sided plywood.