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Vapor Barrier

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Oct 08, 2013, 11:36 PM
Vapor Barrier

I am currently finishing my basement and have a question on where the vapor barrier should be. I live in the mid-west United States, in St. Louis, MO. We have very hot and very cold seasons.

I currently have a vapor barrier that is just a think polyethylene plastic sheet that drapes down the concrete wall and is under the bottom framing member (metal studs), so it is between the framing and the concrete wall.

I am getting contradicting information, but more information is telling me that it needs to be on the inside of the framing before the Sheetrock/drywall.

Can someone confirm the correct location of the vapor barrier? Or if it is necessary at all? Also, what type of insulation should I use if any?

Oct 09, 2013, 09:52 AM
Here is a great article from a source I trust.

First thing I would do is test your basement walls and floor for water vapor penetration from the ground. Tape a piece of plastic or aluminum foil to the wall in several places and on the floor in several places. Tape all four sides, if after a few days the wall or floor behind the foil is wet you have water vapor coming in from the ground. YOU DO NOT want to encase this in plastic, you will cause mold problems if you do. A coat of dry-loc or Thoroseal can keep water vapor at bay. Craftpaper facing on fiberglass is all you want for a vapor barrier in a basement. Using a drywall without a paper face is a good thing on below grade walls as well.

General Disclaimer

Any advice given here is general in nature and is not necessarily valid for your given area. If in doubt check with your local codes enforcement department for what is required when doing electrical, plumbing or structural work on your house. Permits may or may not be required in your area and home owners may not be able to DIY some tasks. I have no way of knowing if you have the skills needed to complete the tasks you are asking about, when in doubt seek professional assistance.

My advice may be worth exactly what you pay me for it. :-) For the record I did not stay in a Holiday Inn Express last night.