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Sealed rigid foam board good enough drainage plane?

user-227802 | Posted in General Questions on

OK, I need your thoughts on this. I’m at home for a few weeks and I forgot to bring home my reference material for drainage planes from work. I’m tearing off old 90 year old siding and 15 # felt and replacing it with 1″ rigid foam and fiber cement board siding. I’m doing one side of my house per year. Last year I left the felt on,as a backup drainage plane and used weather-seal tape all around on the foam. On this side, the felt is poorly installed so my plan is to rip it all off. I realize I’ll have to pay great attention to all seams, but it would be a lot less work if I could put the foam directly on the underlayment sheathing. (some shiplap boards, some dropped siding used as sheathing)

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  1. Expert Member
    ARMANDO COBO | | #1

    Yes, but installing a back-up WRB is better, wise and cheap insurance.

  2. GBA Editor
    Martin Holladay | | #2

    I agree with Armando.

    However, if you insist on using rigid foam as your WRB, here's an article that tells you what you need to know: Using Rigid Foam As a Water-Resistive Barrier.

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