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Community and Q&A

Ice & Water Shield over OSB

ururk | Posted in Green Building Techniques on

I’m going to be putting Ice+Water shield over a barn I’m insulating on the outside. The OSB is gapped (1/8″). Will the gaps pose a problem for the water shield? These gaps will be visible on the interior for at least a year. Should I use a flashing tape first (like 3M’s All Weather Flashing) on the seams first, before covering the siding? Grace (and other mfg’s) of the peel and stick warn you not to have it exposed to living spaces. I’m also concerned that the Ice+Water will not be tough enough to span the largest of the 1/8″ gaps.


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  1. GBA Editor
    Martin Holladay | | #1

    Is this a barn (shelter for farm animals) or a building that will be occupied by humans?

    I'm fairly confident that the Ice & Water Shield will be able to bridge the gaps without any problems.

    If you (or other humans) will be living in the barn, and you are worried that the adhesive on the Ice & Water Shield will outgas, I suppose that installing the 3M flashing tape would make sense (especially if you or your family members have issues with chemical sensitivity).

  2. ururk | | #2

    It will be a wood workshop (and upstairs home office space). As for chemical sensitivity - no, but the precautions on these types of products mention "do not install where this product will be exposed to living spaces" - I'm not too sure if that is due to odor, or voc's (or both) escaping from the product as it ages. I know there are concerns with OSB as well, so the surface area of exposed Ice & Water Shield will be far below that of the OSB and perhaps I'm worrying over nothing.

  3. charlie_sullivan | | #3

    If your only goal is to block outgassing, you could probably get away with something a lot cheaper than 3M flashing tape. Al foil is particularly good at blocking vapors, although the cheap versions of Al foil tape are not particularly robust, so it wouldn't do much to address that concern. But I am not worried about the toughness of Ice and Water Shield for those gaps.

  4. ururk | | #4

    Thanks! I'll do some tests this weekend.

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