Basement Insulation and Building Walls

Old 01-24-03, 08:49 PM
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Question Basement Insulation and Building Walls

I am getting ready to finish my basement. My house is 1 year old and I am still having a little moisture on some of the basment exterior walls. I am running dehumidifiers, but it doesn't seem to be keeping up. I want to build stud walls, insulate them with fiberglass insulation and then drywall for a nice finished look. I am planning on leaving about a 3" gap between the exterior block wall and my stud walls.

My questions is:
(1) Would you recommend I put a plastic vapor barrier on the block walls or is the 3" gap between the block wall and stud built wall sufficient to protect my new finished stud built walls?

I am trying to finish my basement as economically as possible because we are already one of the higher retailed houses on our block. So, my wife wasn't crazy about using expensive products like Drylock to seal the walls completely.

Thanks for any advice.

Old 01-25-03, 07:46 AM
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I guess I will attach my 2 cents worth onto this but I suggest that if you have that much humidity in your lower level, the investment you plan on doing to remodel the lower level should be protected. I would apply the DryLok and do it right for protection, regardless of the other houses or the Mrs. unless she wants to pay for the damages incurred by the moisture.

I guess this is the best and most economical way to construct walls that would be placed on the exterior. I prefer to see 2x4 but as mentioned by others they can get 2x3's. You still need that W/T plate. Doing the framing 16" O.C. provides a solid base for your 1/2" drywall.

The reason to keep the wood out from the walls is the moisture that could damage them. Using larger insulation like R-19 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 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. 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* You can then put paneling over this if desired to met code.

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.

Let me add one other thing, rigid insulation used on a concrete/masonry surface is fine. Considerations to make in using this is;

1. Alternative which does add cost is to apply full rigid sheets to the concrete/masonry walls, adhesively applied, then place frame wall against the rigid, then insulate between studs and cover with drywall. The rigid does then act as a vapor barrier. Do not tape/seal the seams. This allows it to breath and dry up any condensation that may form.

Hope this helps!
Old 01-25-03, 08:44 PM
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Thanks for the information. I am in favor of leaving the larger gap between the masonary block wall and the stud w/drywall built walls and allowing for air flow. The walls WILL NOT be touching one another, but I wasn't sure about the overall moisture in the basement, which could lead to other problems (mold, mildew, etc).


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