Stud wall against slab foundation wall and barrier

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  #1  
Old 03-02-06, 06:54 PM
Alec
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Stud wall against slab foundation wall and barrier

Can you put untreated 2x4 stud walls directly against (not attached to) the foundation slab wall when finishing off an basement? (Sole plate is treated 2x4) How would that react with a vapor barrier? Would the wood mildew and rot due to not much of an air gap?? Normally I would float the stud wall off the slab wall creating a air gap, but I cannot with this wall due to limited space and the need for strong 2x4 studs. (Don't want to use 1x1's,Don't want to lay treated 2x4's flat on the slab glued and nailed $$$)

Its not an outside wall. Above this slab wall is a firewall that separates the back of my garage from the inside of my house. The end of this wall butts up against an outside foundation house/garage side wall. I do not fore see any moisture problems.

If you can,do you need seal the concrete first to protect the wood from contact with the slab?

If you sealed the concrete with any type of sealer or even a radon sealer wouldn't that just create a double vapor barrier once you finish the wall with insulation and drywall? Or is it easier, to just use treated 2x4 lumber for the studs and finish normally? Metal studs?


Thanks Al.
 
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  #2  
Old 03-02-06, 07:54 PM
Join Date: Mar 2005
Location: USA
Posts: 6,126
Stud wall against slab foundation wall and barrier

Radon sealers are designed to stop the transmission of gas vapors (radon gas). I guess that makes them vapor barriers if they are really effective.

Paint-type waterproofers are often vapor barriers if they are applied thick enough to be effective waterproofers.

Cement-based waterproofers (similar to Thoroseal, etc.) are normally not vapor barriers because of the chemical and physical composition of the cured surface.

There is no definite deviding line between vapor barriers and something that is not a vapor barrier. As an example, a thin poly layer is not a vapor barrier until it gets thick enough and then it is magically a vapor barrier (by code definition). All of a sudden one mil makes a world of difference when it is really a gradual change.

Anything if it is thick enough, is a vapor barrier. Since this is the reality, far too many people fret, worry and split hairs about vapor barriers.

Dick
 
  #3  
Old 03-03-06, 04:39 AM
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Join Date: Jul 2005
Location: Ottawa, Canada
Posts: 857
Originally Posted by Alec
Would the wood mildew and rot due to not much of an air gap?? Normally I would float the stud wall off the slab wall creating a air gap, but I cannot with this wall due to limited space and the need for strong 2x4 studs.
You do not want an air gap behind your insulation. This will actually cause some real problems...here's why:
http://www.joneakes.com/cgi-bin/getdetailscals.cgi?id=743
 
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