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Can closed cell spray foam be used to flood proof a wood framed plywood sheathed wall?

Remodelpro | Posted in Energy Efficiency and Durability on

I am rebuilding a small building that was flood damaged by Hurricane Irma. I can not practically raise the floor. I was wondering if the interior was finished with PVC baseboard and the stud cavities were insulated with closed cell spray foam would this prevent me from having to remove the drywall and wet fiberglass insulation if it floods in the future? Would the plywood sheathing and framing be able to dry? The exterior wall assembly is 1/2 exterior plywood covered with #15 felt and hardiplank (no rainscreen). Any suggestions are appreciated

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  1. GBA Editor
    Martin Holladay | | #1

    You can't use drywall and PVC baseboard to waterproof a wall. In a flood situation, even 2 or 3 inches of water will damage drywall enough to require the damaged drywall to be removed, and I can't imagine any way that you could install PVC baseboard that would keep the wall watertight.

    I suppose you could install 6-inch wide PVC baseboard with the drywall sitting above the baseboard (instead of behind the baseboard). If you did this, detailing the joint between the bottom of the drywall and the top of the baseboard would be tricky but possible. This approach would keep the drywall dry, as long as you had only 5.5 inches of flooding. If you had 6.5 inches of flooding, you'd still have to remove damaged drywall.

  2. Remodelpro | | #2


    Thank you for your prompt response.
    My plan was to keep the drywall 5.5 inches off the floor and use 6" PVC baseboard spaced away with 1/2" spacers on the studs so it would overlap the drywall and not be so difficult to detail. Alternatively, I could remove the drywall up 24", Insulate that portion of the wall cavity with closed cell spray foam and install PVC wainscoting. My primary concern is that the studs and exterior sheathing would be able to dry after a flood..

  3. Tyler_LeClear_Vachta | | #3

    Joe Lstiburek wrote an article recently, suggesting the closed cell foam method with a rainscreen over brick.

    I know that is different from your approach. One thing recommended in a JLC article years back was that the wainscoting be removed (or the baseboard and molding) after a flood to allow air to circulate into the stud cavities.

  4. Tyler_LeClear_Vachta | | #4

    Another resource distributed by LSU that has some elements common to your design:

  5. user-2310254 | | #5


    The OP was asking about interior wall strategies for a flood prone structure.

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