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Community and Q&A

OSB vs. Zip System

ddubx6 | Posted in Green Building Techniques on

Quite often I here about the problems with osb and moisture. It holds moisture, it falls apart, etc… Does this apply to zipsystem sheets or does the coating and glues they use put it in a different category? I have had to replace failed/rotted osb in the past and I switched to zip system because I was told this would not happen. Is this true???

I recently built an addition, when finished it will have 4″ of iso on exterior, taped zip system, 2×4 walls with roxul batts, membrain, and then airtight drywall, but do to time and money issues the project is on hold for the winter, just framed and zip system taped. My concern is the moisture that is collecting on the walls, even with plastic I could not achieve keeping all the moist warm air from the existing house out, should I be worried about this, it is quite wet and even freezing now temps are cold in zone 6. I would prefer not to have to heat an uninsulated space all winter . Will the walls rot or will I just have to clean up the mess in the spring?

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  1. GBA Editor
    Martin Holladay | | #1

    Zip System OSB holds up better to rain on the job site than ordinary OSB.

    Any brand of OSB can rot, however, including Zip System OSB. Plywood also rots, as do boards. With adequate moisture and warm temperatures, all of these products will rot.

    Zip System OSB hasn't been on the market long enough for anyone to claim that it is slower to rot than ordinary OSB. It doesn't swell as much as OSB when it is rained on at the job site, and that's good. But I imagine that fungi will still attack it under the right conditions.

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