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Are multiple layers of housewrap any benefit or harm?

mikeysp | Posted in General Questions on

I am in zone 4a.

I recently acquired a BUNCH of typar housewrap. 

Is there any benefit, harm if I use multiple layers of housewrap? 

Currently, I will air seal OSB on my stud wall, then place 3.5″ of Polyiso outside of the OSB and cover the polyiso with the housewrap, then rainscreen and siding.

However, I was thinking why not put a layer of housewrap over the OSB and then another layer over the polyiso as it will cost no money and little time.

Thank you for your advice. 

-Mike

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Replies

  1. Expert Member
  2. GBA Editor
    Brian Pontolilo | | #2

    Hi Mike.

    In your assembly, an additional layer of housewrap won't do any harm. Make sure you are specific about which layer is the WRB and drainage plane so that you integrate all flashing there and avoid mistakes that could creep in with two WRBs.

    1. mikeysp | | #3

      Brian, good point about selecting the WRB layer for drainage plane. Will be outboard layer as that is where my vertical 1x for rainscreen will be, as well as my deep frame for windows.

      Is it a waste, or is there some benefit to the second layer?

      1. Expert Member
        Malcolm Taylor | | #4

        Mike,

        There is no real benefit to the first layer over the OSB.

        1. mikeysp | | #5

          I should have figured that out as I have never seen it; however, when I saw the boatload I acquired, I thought it was worth asking. Thank you.

      2. GBA Editor
        Brian Pontolilo | | #6

        I agree with Malcolm. No harm, but no real benefit either.

  3. Expert Member
    Akos | | #7

    The one benefit of the inner layer is that it will protect your building during construction.

    If it is going to take you a while to install the exterior rigid+wrb, it might be worth it if you are in a rainy climate.

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