Replies

1. 
   Guest_ | Aug 21, 1999 12:34am | #1

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   TinaG,

   I've seen other builders install TYVEK this way. I always install it on the outside to take advantage of the water repelling properties. I also tape around my windows and tape all joints and wrap the band which would be hard to do using the under sheathing method.

   If you are using siding, you should have a water barrier to divert water that penetrates the exterior finish away from the wall framing. If you are using brick you still need a water barrier, either felt or TYVEK.

   There has been much debate on this forum in the past about the advantages and disadvantages of housewrap. You can check the archives for more informaiton.

2. 
   Nick_Pitz | Aug 21, 1999 02:18am | #2

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   This subject is sure to attract a lot of different opinions. I won't claim to be an expert but I have to say I have never heard of housewrap inside the sheathing. I don't use housewrap, I prefer 30 lb. felt, but housewrap is said to have two main functions: to limit air movement and to act as a barrier to bulk water. If it is installed under the sheathing, it will have so many holes from nailing (assuming the sheathing is nailed properly) that it would not be very effective at limiting air movement. Obviously, underneath the sheathing it will not work to shed bulk water, either. Again, I don't claim to have be an expert, but at a minimum I would have him wrap the outside of the sheathing. It is remotely possible that this could actually trap water vapor in between the two layers of housewrap, causing an even bigger problem. An alternative would be to have him use 15 or 30 lb. felt outside the sheathing, which is said not to trap moisture. Other people I'm sure will have other opinions but in my experience this would be the best choice short of having your builder rip off the sheathing, something i am sure neither you nor he want.

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   Tedfrd | Aug 21, 1999 07:15am | #3

   *Tina, Ditto on not wrapping inside of sheathing - especially with OSB, but then again I'm not a fan of tyvek, etc. Like Nick, I've used tar paper for years for the same reasons, (even under vinyl siding). Tar paper is self sealing around penetrations.Instead of taking a chance on trapping moisture between two layers of Tyvek with OSB, which loves to absorb water, two options1- leave as is, but keep a careful eye out for puffing or obvious sheathing damage.2- (I like this one better) Wrap the house outside, then go back inside and either slash or remove the inside layer with a utility knife.By the way, if the contractor has been "always doing it that way", can he show you jobs done like that with 5+ years and no sheathing damage?By the way, what's the climate like where you are?That could make a difference too.

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   Guest_ | Aug 21, 1999 07:01pm | #4

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   Thanks for confirming my gut feeling about all this. We're in western New Mexico at 8200 feet. Not a lot of moisture (about 12-14 inches/year) but it can blow HARD, both rain and snow, so we're worried about infiltration. We'll definitely have him slash interior wrap. Now must decide on outside barrier -- felt or tyvek? We'll probably use Hardiplank siding.

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   Guest_ | Aug 21, 1999 07:28pm | #5

   *Glad to read tha you're not using vinyl...it's probably the worst for stopping rain infiltration from wind-driven rain. OSB is a sponge, you'll definitely need an exterior wrap to minimize water contact. I agree with Tedfrd's recommendations to rewrap and slash the old.I've got no complaints with either Tyvek or felt, though I'd use 30# felt if you go that route. If you do use tyvek, still have your builder wrap the windows with felt strips, properly lapped for drainage. Also, regardless of your wrap, I'd opt for a rain screen. To me it's an especially important detail when high winds, thus possible water penetration, are an issue. Added cost for the detail is minimal. Added peace of mind with OSB? Priceless.I lived in New Mex, though in the SE, for a spell. Though as I remember, wind-driven sand was more of an issue back then!Regards, Mongo

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   Guest_ | Aug 21, 1999 07:54pm | #6

   *Mongo. I'm no lover of vinyl. but wouldn't vinyl siding give one the rain screen? GeneL

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   Guest_ | Aug 21, 1999 08:50pm | #7

   *Out here in stucco land, we know what everyone would do well to learn. Learn it and you will never go wrong.Siding has two purposes: 1) To protect the primary barrier from physical damage and UV degradation. 2) It is decorative. Once you apply that lesson, the waterproofing benefits of siding become redundant in the good sense of redundancy: an additional barrier. Next lesson: All waterproofing needs at least one level of redundancy. Now ask yourself: What is one good reason for putting the house wrap under the sheathing? What is one good reason for putting it over the sheathing? Isn't the answer obvious.

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   Guest_ | Aug 23, 1999 12:35am | #8

   *In response to Mike, I have one good reason NOT to wrap under the sheating (okay, this might just be a question). Assuming you frame on the deck, I would think that it would be more difficult, time-consuming, and risk punching holes in the wrap if put directly on the studs. With out the sheating to walk on, I would think this would be tricky, or do they just not nail, and let the sheating nails secure it? My personal favorite is to wrap the walls after erection (especially if only one story tall). This way, there are fewer breaks in the coverage. BTW, why even consider using OSB? Around here, you only save $1.00-1.50 per sheet; assuming a 1500 square foot house, the difference is $50-75. With all the concern about off-gassing, and the defenite "sponge" characteristics, I would think that this would be a no brainer for builders. Just a thought.Jon Blakemore

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   Guest_ | Aug 23, 1999 07:41am | #9

   *Jon,Just a tangential note to your comment about the off-gassing concerns of OSB. I can tell you are no fan but one of my recent clients with chemical sensitivities checked with the APA regarding the formaldahyde content of OSB and CDX ply. Seems OSB has less phenolformaldahyde adhesive than plywood. Phenol glue is 'better' than urea glue (those usually found in interior plywoods like those in kitchen cabinets). I know this may not sway you're opinion of OSB but I found it compelling information contradicted my gut feeling.

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   PRP | Aug 23, 1999 10:47pm | #10

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   Jon: I think Mike M. was suggesting that it was a no brainer to use housewrap after the sheathing is in place. Mike, correct me if i'm wrong on your inference. Tina needs to do some certain scrutinizing of this builder.

   One other thing Jon, Other thing: Housewrap is an infiltration barrier - for moisture and air. You suggest that some builders put housewrap on two-storey homes in section on the wall while it is laid horizontally on the deck. That, and I'm glad you don't practice it, is potentially wrong. This would leave areas where air infiltrating to work directly into the home -- at joints between the plates. It is easier to install, better to install, recommended to be installed while the walls are vertical, on the outside of sheathing, of course.

5. 
   Guest_ | Aug 25, 1999 05:22pm | #11

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   Mike,

   Okay, so my predjuice against OSB has broken through. Still, my question stands. Can you honestly tell me that you regard OSB and CDX as equals when it comes to resistance to de-lamination? I don't think you can. So maybe the off-gassing thing was a moot point, but I stand firm that $1.50 per 4'x8' sheet in savings is not worth it.

   Jon

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   Guest_ | Aug 27, 1999 08:37pm | #13

   *Hi Tina,You might ask your builder WHY he wraps houses like that. Maybe he thinks Tyvek is meant to ventilate and needs 10,000 nails driven through it. Anyway, it is supposed to be a one-way barrier, and if it is, and both layers on each side of the osb are installed facing the right way, technically you should be okay. However, there is debate if this really works, kind of like Gore-tex, which I know does not work. If he rewraps, and slashes his first wrap (which should be free) you can probably sleep without any more worry than 50 million other tyvek gamblers!Scott ps I'm sure the "free" part will make a lot of my fellow builders uneasy, to say the least! Sorry, I hate sh**ty work.*****

6. 
   TinaG_ | Aug 27, 1999 08:37pm | #12

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   Our contractor put the housewrap INSIDE our OSB (in other words, between studs and OSB) instead of wrapping the outside. He did each wall this way. Doesn't seem right to us, but he said he's always done it that way (how often have we heard THAT?!!) I thought wrap was supposed to do just that, WRAP, so that OSB is also protected. He's offered to wrap outside as we expected in addition to the wrap he's already done inside. Or will what he's done be ok?