where does the vapor barrrier go


Old 12-31-09, 02:49 PM
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Join Date: Dec 2009
Location: maryland
Posts: 15
where does the vapor barrrier go

I am rebuilding my basement. It has been entirely gutted; the enture basement was moldy from a very bad basement buildout coupled with poor maintenance of gutters and downspouts. The below grade walls are cmu and the below grade waterproofing has degraded over time. The house was built in 1964. I had an interior perimeter french drain and sump pump system installed to handle the seepage at the intersection of the slab and the base of the wall. However, "tear dropping" through the cmu walls is still a possibility during heavy rain events. Miradrain has been installed at the base of the perimeter to pick up any drips that come through the wall. I plan to frame the exterior walls with 2x3 framing held 1" +/- off the wall. The basement will be heated and cooled. I plan to install unfaced batt in the perimeter framing. My question is - where do I install the vapor barrier - inside of stud, outside of stud, or apply a membrane to the cmu? Or is the vapor barrier a good idea at all? We live in Maryland which has cold winters and extremely humid summers. The basement is 3 sides underground with one side walkout.
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Old 12-31-09, 04:52 PM
Join Date: Oct 2008
Location: New England
Posts: 9,991
Hi Terrence and welcome to the debate. Not that one in particular is doing on on the board, but there is a constant debate as to how to finish basements. Do you try to seal the water/moisture out? Which rarely works. Or give it a place to go and allow for evaporation of wet areas. I opt for the later and try to avoid batts.

First, the above grade foundation areas, plus one foot below grade, are the biggest heat loss areas. And they can tolerate a vapor barrier as they walls can dry to the outside. Below that, an inch or two of pink or blue rigid foam attached directly to the walls will still be able to dry to the inside yet insulate well.

However, if you are dealing with water leakage I generally say that has to be resolved before anything goes up. You certainly don't want to do this again and you are already dealing with an old mold problem which raises concerns for future buyers and insurance companies. The fine print on what is covered related to mold has gotten tough since Katrina.

I'll get out of your way and leave you with some reading.
RR-0509c: Renovating Existing Basements —
Not sure if there is anything on this one to help, but the do discuss wet walls. Wet Wall Proposal


That should get you started.


Last edited by Bud9051; 12-31-09 at 04:53 PM. Reason: wrong button

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