How do I attach plywood over 2“ x 6” deck boards in preparation for a waterproof cover?

Question

My two decks (12'x26' and 12'x14') are in good shape. Minor rot has been repaired.

I am applying 5/8" Tongue & Groove plywood over the 2x6 deck board as a base for 68 mil vinyl covering. I know I need to align the plywood end butts solidly on the 2x6, but I am not sure of the size of the end gap, 1/8"?

I am also unsure of the spacing of the deck screws that I will be using to secure the plywood to the 2x6. I believe 12" spacing may be adequate on both the edge and the field of the plywood?

Deck specs:

• Joists are 2x8 on 16" centers and running perpendicular to the house, the gaps between the 2x6s range from 1/8 to 1/4".
• The long side of the deck is fastened securely to the house with a ledger board and hangers.
• The outboard deck supports are 3-2x10s fastened together, with those being supported by 6x6 posts on concrete pillars.
• There is appropriate grade away from the house.

I was finally able to get in touch with the manufacturer. mfarver, they echoed your comments and also told me to leave 1/16 between the butt ends of the plywood.

Answer 1

The proper answer to your questions is "find the manufacturer of your vinyl and follow their installation guidelines". They can give you answer to all of the questions that you are asking.

Answer 2

If you are planning on never putting a rigid flooring (tile) atop the plywood you don't need a lot of screws. Typically the rule is 6" on the perimeter, and 12" in the field. Get screws long enough to go into the underlying joists where possible. Use construction adhesive.