Second layer of housewrap
AndyZb
| Posted in Green Building Techniques on
I have a 2×6 Wall with sheathing then tyvek, then 2 inches mineral wool, then 1×4 strapping/furring strips. My builder put a second layer of tyvek on top of the furring strips. Will this affect the function as a rain screen? The window flashing is to the first layer of tyvek deep to the mineral wool. I am not entirely sure I understand but I think he wanted a second layer just in case because of all the holes from placing the furring strips and exterior insulation. I was wondering if it will interfere with the drainage plane for the rain screen. Thanks!
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Replies
Hi Andy.
I'm not sure why your builder added the second layer of Tyvek over the furring strips. That's not a common part of a rainscreen assembly. The rainscreen gap should be vented at the top and bottom and should allow water to drain. As long as the Tyvek isn't installed in such a way as to block air flow at the top or bottom of the gap, or to block water from draining at the bottom of the gap, it shouldn't be a problem. If it does, you'll want to rework the details at the top and bottom of the wall. You may find this article helpful: All About Rainscreens
Thanks Brian, they have never done exterior insulation before and I think they are just tryimg to be proactive. They thought it would be extra insurance against water intrusion.
I did read the rainscreen article. Martin implies that even a minimal gap should still work so I imagine that as long as the tyvek is not pulled tight there still should be a small amount of space between the tyvek and siding.
What's the siding going to be?
Hardie fiber cement; some lap boards and some board and batten
I think that second layer of house wrap might add some risk, by limiting the ability of the Hardie siding to dry. My thinking is it might slow drying on the back of the siding if any water gets in. I can’t say I’ve ever tried an assembly like this though, so I’m guessing. If it was my own house, I’d want the siding directly over the rain gap with nothing flapping around in the gap.
Bill
Ok thanks for you time!