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Attaching a vapor barrier to the wall in a crawlspace?

Attaching a vapor barrier to the wall in a crawlspace?


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Old 02-02-16, 08:21 AM
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Attaching a vapor barrier to the wall in a crawlspace?

I plan to install a VB in my crawlspace and run the VB apprx 6" up the perimeter brick wall. How should I attach the VB to the brick wall? Thanks.
 
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Old 02-02-16, 08:27 AM
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Brush on some mastic. Air duct sealant would work.
 
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Old 02-02-16, 11:27 AM
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Air duct mastic will certainly seal the VB to the brick but how long it will HOLD the VB (I'm assuming polyethylene) is debatable. As I posted in a different thread, very few adhesives will stick to polyethylene and so a secondary method must be used in addition to just a sealant. I recommend using battens about 3/8 to 1/2 inch in thickness and at least an inch wide to go over the poly/mastic layer and then held in place via drive pins or tapcons or some such fastener.
 
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Old 02-02-16, 11:31 AM
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What type material are battens? plastic? Also, what is the recommended safe range for humidity in a crawl space?
 
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Old 02-02-16, 11:33 AM
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That's a good point, Furd. I should mention that 2 coats of brushed on mastic would generally be needed. One to stick it to the brick, another to cover the top edge/front of the poly and actually embed it in the mastic.

Nothing wrong with adding the batten either if you want to go to that extent.
 
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Old 02-02-16, 12:13 PM
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Battens are generally wood, about an inch wide and 3/8 inch thick, more or less. Length about six feet or whatever can be easily handled.

Also, what is the recommended safe range for humidity in a crawl space?
Safe for what? If the crawlspace is ventilated to the outside air the humidity will be about the same as the great outdoors which could be as high as 100% when it it raining, depending on the ambient air temperature. If the crawlspace is NOT ventilated then the humidity should be about the same as the living spaces, 40% to 60% is generally acceptable. If the humidity, I actually should be calling it RELATIVE humidity as it is in relationship to the air temperature, is higher than 60% it really should have a dehumidifier operating in the space.
 
 

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