Yet another V/B Question

Old 07-19-04, 08:14 AM
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Yet another V/B Question

Hi guys,
I stumbled across this forum and now I'm concerned! I purchased my home in PA about a year ago, and I'm in the process of fixing the moisture problems the sellers never had before.

Anyway, the foundation is poured and leaking at the cold joint at the bottom. The seller had installed sheetrock in, say, 50% of the basement to make a nice living room and exercise room. I've had to tear away the bottom 2' of the wall to install a cove molding system, but my question is about the vapor barrier - there is none. The basement has 10' walls, so I'm not interested in tearing down hundreds of square feet of sheetrock and insulation if I don't have to.

The studs are about an inch from the wall, and air can get back there through the openings at the ends of the walls. Do I need a vapor barrier in this scenario?

Thanks in advance,
Old 07-19-04, 07:44 PM
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If it is cold and you would like to insulate, the answer is yes.

If it were me, I would want to install a vapor barrier. Read below to reasons why. Here is what is normally done and required by Code, remember this is one way but considered the best way.

Doing the wall framing 16" O.C. provides a solid base for your 1/2" drywall. If using traditional framing method, frame your new wall 1" from the vertical block/masonry surface if using R-13. The reason to keep the wood out from the walls is the moisture that could damage them. If using insulation like R-19 and only 2x4 studs, the insulation would touch the walls. I have stated before that if a homeowner did put thicker insulation in, and the wall was only 1" from the masonry surface, I have recommended hanging a vapor barrier between the back of the wall and masonry surface. This doesn't allow for the insulation to touch the wall and air movement is not restricted but at least you won't create damage to the insulation or wood.

Vapor barrier should be placed directly under the drywall. The warm inside air containing water vapor can get past the wall finish and insulation and condense inside the colder wall cavity. If enough of this happens, and the water cannot escape, wood rot, mold, and other moisture-related problems are likely to occur. For this reason, building codes often require installing a vapor diffusion retarder on the warmest side of the wall cavity. This is what is required in Minnesota;

If you do want to increase the R value, move the wall out further or use the R-13 and then apply a rigid insulation over the studs (warm side) then drywall (not paneling) *Code advises a 15 minute fire rated material over any rigid insulation - 1/2" Drywall*..

Kraft Faced insulation is fine to use in the above scenario. No need for the poly and you can do everything easily. You may find this easier and I would do this versus unfaced and vapor barrier because I don't like to play with it any more than I have to.

Hope this helps!

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