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House wrap--if one layer is good then 2 must be better, right?

House wrap--if one layer is good then 2 must be better, right?

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  #1  
Old 11-05-14, 06:37 AM
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House wrap--if one layer is good then 2 must be better, right?

I'm having an attached garage added to my cottage and the builder didn't use the specified wrap. I wanted the dimpled rain-drainage type because I'm hanging cedar siding on it but he used regular Tyvek-type smooth film.

Can I just staple up a 2nd layer? On an unheated garage I can't think of a downside to doubling up on the barrier.
 
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  #2  
Old 11-05-14, 06:54 AM
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Did you have a contract with the builder that specified a particular housewrap and the method it would be applied? If yes, then tell him to follow the contract or you will sue. He will likely respond with an offer to lower the price of the job if you just accept what he did; at that point you have to make a judgment call as to whether or not the specified wrap is acceptable vs the cost of the court case.

AS for simply adding another layer of wrap...not my area of expertise but I would think that is not an acceptable option.
 
  #3  
Old 11-05-14, 03:18 PM
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Tyvek is a weather resistant barrier. Not sure what "dimpled" covering you are referring to. I would not add a layer to an existing one. It will breathe, but adding another layer may stymie that ability.
 
  #4  
Old 11-05-14, 04:27 PM
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I can't comment on whether two layers would be bad, but don't settle on what he put there.

From Dupont:

"Yes, Tyvek® DrainWrap™ can be used under cedar siding. It is recommended that the cedar siding be installed per manufacturer’s guidelines and recommendations by wood siding associations, such as the Western Red Cedar Lumber Association. This requires priming all surfaces, including the back and ends, before installing. Additionally, the use of furring strips will help promote drainage of any incidental water that may penetrate the cedar cladding."

Found this old thread about tyvek and cedar shingles: cedar shingles and housewrap | Fine Homebuilding | Breaktime

The tanins in the cedar allow water to go through the tyvek. So the shingles need to be back primed or on a rain screen to prevent contact with the wrap.
 
  #5  
Old 11-05-14, 06:03 PM
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DuPont will claim up and down that you can use Tyvek under cedar, but I wouldn't.

I would not think twice about putting another layer over the existing. Like you said, it's a garage. If it was a heated room it might be different. But IMO it would still be fine. 2 layers of vapor permeable housewrap aren't going to suddenly become a vapor barrier if you lap one over the other. Sure it might slow the vapor transmission, but I "doubt" it would be enough to cause a problem. IMO.
 
  #6  
Old 11-05-14, 08:41 PM
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I'm not going to sue my builder or make him do it over. it was an honest mistake. I had purchased the roll weeks ago. He sent his son into the shed to fetch it but brought out the wrong one.

I'm curious to hear Bud's opinion on this.
 
  #7  
Old 11-06-14, 12:10 AM
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Well, if you had told us that in the original post I would have never suggested suing. My experience is that it is usually best to have the contractor supply all materials as specifed in the contract rather than the owner supplying. Less hassles down the road as to proper materials being used.
 
  #8  
Old 11-06-14, 02:21 PM
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This might be a more appropriate product for cedar shingles: Drainable Housewrap Products | Benjamin Obdyke
 
  #9  
Old 11-06-14, 08:41 PM
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There are many, of course. Being an unheated garage, I don't need the best. On the house I used this:

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  #10  
Old 11-06-14, 09:47 PM
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I see no problem with adding a second layer over what is there as the vapor properties of different materials vary so much anyway. The first layer of house wrap would be very vapor open. A second layer would slow drying to the outside a bit, but so would many sidings, but your cedar is not one of them. Your cedar should have the dimpled drainage plane, far more important than two layers of vapor open wrap.

Of concern for all unheated garages in cold country is pulling in a vehicle covered with 2 feet of snow and letting that melt. That water has no place to go with a traditional wall, drywall, insulation and then sheathing. Limiting the peak loads of water solves 90% of the moisture issue before it gets to the walls.

Enjoy,
Bud
 
  #11  
Old 11-07-14, 06:09 AM
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Thank you Bud9051 and XSleeper for answering my question.
 
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