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This question comes from Wally. Hi Steve, how are things? One of my retirement projects is our
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cottage. We pretty much gutted it two years ago and have been slowly rebuilding since. We're
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finally getting around to the siding, a combination of vertical board and batten and shakes, all vinyl
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My question is about Tyvek. When we resheet the outside of the cottage two years ago with half
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inch plywood, we covered it with Tyvek, which is a kind of building wrap. I'm a bit concerned with
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having the Tyvek exposed to the elements for this long. My question is should I replace the Tyvek
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before residing or am I safe to reside over it? Well, technically speaking, Tyvek is a fabric
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a kind of a waterproof fabric that's wrapped around the outer sheeting of buildings. It's
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used all the time. It just helps to stop air infiltration and drafts and things. It does a
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decent job at that but I don't like Tyvek and I don't use any of the standard building wraps on
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my projects. A couple of reasons. First of all, last time I checked, companies like Tyvek say
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our product has got to be covered in 60 days or less or else it's going to start deteriorating
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and not work properly. That 60 days seems a bit conservative to me because I've seen it up for a
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lot longer than that and it seems to be fine. Another problem though is the way it's not
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breathable. It can't let moisture vapor pass through it. It's waterproof. It's kind of plasticky
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and I can keep water out but if water ever gets behind it, you know, on the wall side of it
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it can't escape. So that's another problem and I've seen that happen. I've also seen a situation
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where a building wrap, conventional building wrap, was used against OSB, oriented strand board. It's
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a common sheathing material and for some reason, and I don't know all the chemistry, but the building
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wrap was tatters. It was just hanging in ribbons and it pretty well deteriorated. It certainly
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wasn't functioning properly. I've heard some people theorize that it's the glue in the OSB
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that doesn't react well with the building wrap. I don't know what it is but my preference is
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to use a heavier breathable building wrap. It's made by a few different companies. Cosella
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Dorkin is one company that makes a product that I really like. It's probably about twice as thick
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as regular building wrap so it's a lot stronger. You have a hard time tearing it but most importantly
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it allows moisture vapor to pass through. So it's kind of interesting. It stops liquid water. If
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there's a leak, it's not going to get through but if water gets behind it, it can dry out through
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this stuff. So breathability is a great thing when it comes to building wraps
