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Vapor barrier in crawl space.


JPicasso's Avatar
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Join Date: Oct 2004
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08-15-05, 08:08 PM   #1  
Vapor barrier in crawl space.

Okay. House is on a three foot crawlspace.
One section of house is an add-on over what used to be the old patio.
it's built over about 80% concrete and the perimeter appears to be dirt.
Floor is 2x6 joists resting on concrete stands running about 2 inches over the old patio.
Kraft-faced insulation between. 1x6 floorboards and then a plastic vaporbarrier, then 5/8" plywood and carpet.
Two heat/cool vents running between joists. (chicago)

Kay. Got it ripped up/down to the 1x6's.
My crawlspace was the old neighborhood rat hotel by the looks and smell of it.
(it wasn't my house at the time)

So, while I have the floor boards ripped up to replace the insulation and inspect the vents,
How am I to put this back together? I plan on a 1/2 or 3/8 plywood with hardwood on top.
I can't get a VB under the 2x6's easily, so that's out.
Water/moisture do not appear to be a large problem, although, it's been exceptionally dry this year. No damage is apparent.

And to think I was just going to replace the carpet.

 
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em69's Avatar
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08-16-05, 05:16 AM   #2  
If I read your post correctly, the VB was previously installed on the warm side of the insulation (on top of the floor boards). Which in your climate is the correct way.

I am confused though why you say you cannot re-apply the VB under the plywood? You need a VB because the addition is built over an unheated space.

Also, for the hardwood, I think you need a minimum of 5/8" ply for the sub floor.

 
JPicasso's Avatar
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08-16-05, 07:24 AM   #3  
I'm pulling and putting back the 1x6's, then some plywood sheets. 3/8 or 1/2, whatever it is that I bought last week.

I can put the VB between the planks and the plywood, no problem.
Just making sure it was done right the first time.

Also, I plan on using 15# roofing felt under the hardwood, does this cause problems with the plastic being down also?

 
chris8796's Avatar
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08-16-05, 02:24 PM   #4  
I also would recommend using a better subfloor. Thats an expensive problem to fix if you do it wrong the first time. check out the National flooring manufacturers website for site preparation guidelines for wood floors. I would also have the plastic vapor barrier somewhere between the plywood and the dirt.

http://www.nofma.org/installation1.htm

 
em69's Avatar
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08-18-05, 11:42 AM   #5  
Ok, so 1x6 and plywood...which 1 inch or more which is sufficient.

As long as the roofing felt is not sitting on the vapour barrier. I'd probably put the VP under the plywood, or under the 1x6s.

 
speedy72's Avatar
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08-25-05, 06:53 PM   #6  
How big a crawl space are we talking here? Anyway I would definately get some more advice on that sub floor or I think you will have real problems with the hardwood. how wide is the hardwood? This is important, if it's wide stuff and the humidity goes up and down your wood will move all over the place. I'm not a pro on vapor barriers but everthing I've read in recent publications recomends putting the vapor barrier down on the ground and insulating the foundation wall with rigid foam board.

 
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