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I bought this plywood and it came very wet so I don't doubt that it is actually GC treated plywood; however, the stamp on it says exposure 1 despite Home Depot's website saying it's exterior rated. I'm wondering if perhaps what happened is that they took exposure 1 plywood and then treated it but didn't put a new stamp, though that seems silly if that's the case. Any thoughts on using this for the roof of a treehouse that will also serve as a deck and be exposed to the elements?

The HD link is https://www.homedepot.com/p/3-4-in-x-4-ft-x-8-ft-Ground-Contact-Pressure-Treated-Pine-Performance-Rated-Sheathing-106128/206971071 if helpful.

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The link is to pt for ground contact plywood. If that is what you purchased and received then it is suitable for a treehouse. I would not rely on it for a roof without some secondary covering such as shingles. If your question is if the plywood you received is the same as depicted in the link, we cannot answer because we don't have a pic of any of the markings on that plywood.

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  • Is the reason it shouldn't be relied on as a roof because cracks between the sheets may form and water get through or because the water exposure may harm the sheets? I was thinking of putting straight line blocking below the seams and filling all gaps with OSI Quad Max or something. It's a flat top roof/deck (0.25-in-12 slope). Thanks
    – g491
    Dec 31, 2022 at 6:11
  • if used as roof decking the panels need to have spacing for expansion and contraction. so filling the gaps is not recommended. The PT grade or exterior plywood still needs this gap and still should have a secondary covering . It is resistant to outdoor elements but not impenetrable.
    – RMDman
    Dec 31, 2022 at 6:13
  • Yeah I was thinking to have the 1/8 spacing but as all joints would be over a joist or blocking, just fill them really well with the sealant and since that's flexible it shouldn't have issues. Any thoughts on this not being a good idea? Thanks
    – g491
    Dec 31, 2022 at 6:15
  • What you are proposing is not a standard procedure for a roof structure. Are you referring to the roof or the floor?
    – RMDman
    Dec 31, 2022 at 6:18
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    Then the wood still need some type of secondary covering to prevent water from infiltrating. PT exterior will resist this longer but will still degrade without it. Using the bare plywood alone is not advised.
    – RMDman
    Dec 31, 2022 at 6:26

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