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Community and Q&A

Zipwall issue

jnarchitects | Posted in Green Products and Materials on

We used zipwall exterior sheathing recently. The walls are 2×6 framed 24″ o.c. When we started putting up the sidewall (white cedar shingles) we noticed that the sheathing had bowed in b/w studs in several locations. This creates a wave effect on the shingles and is quite noticeable.

Huber seems to think that a few of the panels expanded slightly in the width direction causing them to flex in or out.

Has anyone else seen this problem? It was completely undetectable until the shingles were installed. We are going to block the bays with 2 blocks (1/3, 2/3 of height) to try to push the sheathing out. Huber feels that if the panels have moved they are likely not to move anymore as the moisture content of the panels is 12% manufactured.

Thoughts, Opinions….

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  1. Riversong | | #1

    I have no experience with ZipWall because I will not use OSB in any form in my homes. It is a low-quality material that is highly vulnerable to moisture, swelling, mold and rot.

    Huber adds waxes to their ZipWall and Advantech OSB materials, but that's like putting lipstick on a pig. And to expect ZipWall to function as both sheathing, air barrier and weather barrier (with tape on the seams) is an exercise in wishful thinking reinforced by clever marketing.

    This is the first time I've heard of this particular problem, but I'm not surprised that you would encounter it with 24" oc framing, since 16" oc is industry standard. And Huber requires an 1/8" gap at all panel joints to allow for expansion.

    You will not likely be able to correct this waviness, as Huber admits. And they warn against using wet-spray insulation materials or any coatings.

  2. jnarchitects | | #2

    While OSB certainly has its issues, the Advantech products are far and away better than the majority of OSB products available. We never rely only on the Zipwall to function as air barrier and weather barrier alone.

    The panels are also rated to span 24" o.c. without issue (confirmed with sales rep. and techincal rep at Huber). While 16" o.c. might be industry standard, many of us are framing at 24" o.c. on a regular basis without issue.

    All of the panels are run vertically. The panels are self-spacing with an 1/8" gap on the long sides. The 1/8" space, I believe, is only required at seams b/w the 4' sides or where a 4' side meets an 8' side.

    I don't think they warn against using wet-spray insulation. The technical bulletin simply states appropriate moisture contents that should be maintained during installation and ensure proper drying time before sheetrocking the walls. I would think this is no different than the requirements (recommendations) for wet-spray on any sheathing product. Otherwise you are looking at potential mold, rot issues.

    It seems to be a manufacturing defect in some of the panels as it only shows up in some places on the house.

    Thanks for your input.

  3. dankolbert | | #3

    We had a few sheets swell on us on a house a couple of years ago, but haven't seen the problem since then.

  4. jnarchitects | | #4

    Did you guys find any solution or were you able to replace the panels before installing cladding?

  5. wjrobinson | | #5

    Just an FYI add... I inspected a roof recently that was very wavy. Turned out the roof sheathing was plywood. More than one sheet had done this on one half of an attached garage roof.

    It was a name brand plywood but was not five ply. Number of ply's can make a difference.

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