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Community and Q&A

Where to put the water barrier?

user-4977769 | Posted in GBA Pro Help on

I’m going to retrofit rigid foam over a log home in Vermont. The logs are 6 inch pine logs, that have an R value of about 9, they have a clapboard cut on the outside so the house will not appear any different with a 3 inch layer of foam insulation with a rain screen and clapboard.

My question is about where to put the tyvek, on the out side of the foam or under the foam? We are replacing all the windows and doors. It would seem to me that the tyvek belongs on the outside of the foam and over the flanges of the new windows and doors.

The videos, I have seen on the this sight show the tyvek under the foam. As I am not concerned about water getting into the house during the retrofit as the log walls are sealed and I’m not removing siding, would that make sense to put the tyvek over the foam but under the strapping for the rain screen?


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  1. GBA Editor
    Martin Holladay | | #1

    Either way can work. The housewrap is your water-resistive barrier (WRB), and the WRB needs to be carefully integrated with the wall's window flashing, door flashing, and any flashing for penetrations.

    Think through how you want to execute these flashing details, and then decide whether it will be easier to integrate the flashing with housewrap that is under the rigid foam or housewrap that is over the rigid foam. In many cases, the decision hinges on whether your wall will have innie windows or outie windows.

    Here is a link to an article that discusses the issue: Where Does the Housewrap Go?

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