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Water leak through vinyl and plywood on open deck, some locations already sunken due to rotten plywood underneath.

I would like to replace by MDO plywood (Crezon plywood) and then paint on top of the new plywood.

Can you suggest a type of sealant for the joints of each piece of 4' x 8' plywood?

Do you think this is the most economical way of replacing the deck material?

Our ambient temperature is between 30 degree to minus 10 degree Celsius.

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    What problem are you trying to solve? The deck was originally covered in vinyl because you can't seal joints in plywood and expect it to remain water-tight. Wood moves, tearing seams loose. It just won't last, especially under foot traffic. If it did you wouldn't see asphalt shingles on roofs--you'd just see painted plywood.
    – isherwood
    Aug 22, 2019 at 2:33
  • Duplicate: diy.stackexchange.com/questions/171777/…
    – isherwood
    Aug 22, 2019 at 2:48
  • Open plywood? Leaking , a photo may be worth a 1000 words here. If I had only the info you’ll provide today I would use a membrane to seal the deck with a wear surface above that but this is just a comment because I am not sure of the construction, but the rot needs to be removed and repaired first.
    – Ed Beal
    Aug 22, 2019 at 3:56
  • What every your soultion ends up being, make sure that the roof is not flat, even if it's flat and slanted. A slight dome shape will help keep it from developing a low spot that might trap water.
    – NothingToSeeHere
    Aug 22, 2019 at 16:17
  • The typical solution is to seal the roof (usually with a continuous heat-sealed membrane) and then build a floating deck on top of that using dimension lumber "joists" (often just 2x2s) that sit directly on the sealed roof, allowing for run-off. Care needs to be taken to match the load-bearing structures to the foundation. Unless done perfectly, it always leaks.
    – user101382
    Aug 22, 2019 at 20:14

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This is not going to work. Plywood moves less than normal wood, but it still moves. It will be impossible to seal the joints between the sheets.

I would use ordinary plywood or chipboard, cover it with a waterproof membrane (probably EDPM), and then cover that with something else (stone chips, decking, whatever).

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  • The material used to prevent snow dam damage above gutters would work. There's also heavier rubber/vinyl (?) material used to re-roof mobile homes that would be an excellent choice, but it's kind of pricy. As long as you aren't wearing cleats it's very good.
    – NothingToSeeHere
    Aug 22, 2019 at 16:16
  • @Ring Do you mean as an overall membrane, or as a seal over just the joints?
    – Martin Bonner supports Monica
    Aug 23, 2019 at 8:47
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    As an overall membrane. Only covering seams on plywood decks is a waste of time and money. I can't for the life of me remember what is was called. It was a roofing system I helped flog to mobile home owners as a telemarketer many, many years ago. It really was great stuff and I honestly would have sprung for it had I needed such a product. It was impressive.
    – NothingToSeeHere
    Aug 26, 2019 at 16:38

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