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Will Tyvek leak like a tent?


Chris Bernhardt
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Joe L. said that Tyvek leaks via capillary continuity just like when you touch your finger to a tent, and that it works as advertised where it's installed like a tent. IOW, at points where it is directly compressed it can leak, and where it's not, it won't.

Am I misunderstanding his commentary?

Has anyone seen evidence of this in the field?

Joe L. claimed his experiments show that Tyvek in contact with stucco leaked, and leaked profusely. If that is true, why would it not also leak where fiber cement board or any other siding is clamping it to the OSB sheathing?

Chris, Oregon

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Originally posted by Chris Bernhardt

Joe L. said that Tyvek leaks via capillary continuity just like when you touch your finger to a tent, and that it works as advertised where it's installed like a tent. IOW, at points where it is directly compressed it can leak, and where it's not, it won't.

Am I misunderstanding his commentary?

Has anyone seen evidence of this in the field?

Joe L. claimed his experiments show that Tyvek in contact with stucco leaked, and leaked profusely. If that is true, why would it not also leak where fiber cement board or any other siding is clamping it to the OSB sheathing?

Chris, Oregon

I don't have a lot of experience with stucco so I can't comment on that. Otherwise, in my experience, Tyvek behaves exactly as you've described. Further, even without direct contact, I've watched it leak when subjected to heavy wetting and hard winds. The water just beads up on the other side and runs down in rivulets. It reminded me of fat oozing through a sausage casing.

It works great on rainscreens.

- Jim Katen, Oregon

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Hi Chris,

Although I hadn't read that, if Joe L. says it I'd tend to believe it. That aside, the thing that a lot of folks don't understand is that Tyvek is designed to be an air infiltration barrier not a WRB. Water blows through most types of siding at joints and drains to the base of the wall and it eventually soaks through stucco and must be able to drain. Before wrap, builders used building paper. It has a perm factor of about .50 when it's dry but only about .05 when it's wet and therefore it doesn't do a whole lot to prevent air infiltration. However, When building paper gets wet and dries it shrivels up (wrinkles) and pushes the siding outward a minute amount; this allows the wall to drain. Polyolefin wrap doesn't do that; it remains perfectly flat and doesn't swell or shrink in plane.

So, when you wrap a house with Tyvek and then punch thousands of holes through it as you apply the siding or stucco lath, you've only provided thousands of pathways for water to get behind it. Once you've done that, the water that passes through the siding has to be able to get back out of the wall or the Tyvek will hold it there. Compress 12ft. of Tyvek where the top edge of a clap is overlapped by the bottom of another and nailed through the Tyvek to the wall, and you've got a place for water to seep behind the Tyvek and remain trapped just like it's in a petrie dish. Do that dozens of times from top to bottom of a wall and you can understand why it's not the best product in the world and you begin to understand why so many houses wrapped with Tyvek and other polyolefin wraps are rotting. That's the reason why you now see these new wraps that have raised ribs on them and are installed with the ribs running vertically. These allow walls to drain better and are supposed to prevent the siding or stucco from trapping water against the substrate.

ONE TEAM - ONE FIGHT!!!

Mike

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My house is wrapped in Tyvek under cedar siding. If I had it to do over again, I'd install felt paper instead, then ferring strips then the cedar. To be sure, my house would be the only one done that way for miles around and would be the first such installation for the contractor.

Tyvek has its applications but house wrap isn't one of the better ones. Just try to convince an installer of that.

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