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Cinderbolt77 t1_j8zfbpl wrote

Pretty sure you need barrier, regardless of tar on outside, you are going to have condensation on the inside.

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wiseupyabuckejitt t1_j90u7xg wrote

No vapor barrier for below grade concrete walls: water vapor from soil permeates through the concrete and will get trapped in the wall. From buildingscience.com: “Constructing frame walls, insulating the resulting cavity and covering with an interior plastic vapor barrier is common and often leads to odor, mold, decay and corrosion problems.”

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Cinderbolt77 t1_j8zg5xx wrote

Polyurethane sheeting is a typical vapor barrier that contractors use to prevent moisture from penetrating the walls of a basement. The material is stapled to the frame of a basement wall before it is finished with plaster or drywall. A vapor barrier is also helpful to keeping a basement insulated and warm. * https://www.hgtv.com/design/remodel/interior-remodel/how-to-install-a-basement-vapor-barrier

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f_crick t1_j90oetg wrote

They did this in my house, and it caused mold and rot. Moisture will get in regardless of the outside seal, and while the vapor barrier will keep moisture in the wall and out of your basement, it’ll also slowly rot away the framing stuck between the vapor barrier and the wall below grade. It took maybe 20 years, but all the framing where we found a vapor barrier was severely degraded, and framing where there was no barrier was in amazing shape.

If you’re happy to let it rot to have a little less moisture come in, it works, but the lifetime of the framing will be cut short.

I’d advise either sealing with foam directly against the concrete, or skip the moisture barrier. As long as it’s well air sealed, vapor will slowly escape, allowing everything to dry.

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Raleford t1_j90r6um wrote

I don't know your build or what happened, but generally speaking, the vapor barrier is intended to keep moisture out of the wall, not out of the room. In fact it should keep it in the room.

That being said, concrete does sweat, so foam board instead of fiberglass directly on the wall is still likely better and potentially where your moisture came from.

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9oh210 t1_j91fa42 wrote

If op wants to use a vapor barrier in the basement they should be using a smart barrier.

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woodprefect t1_j91p691 wrote

or shellac based primer on the drywall - in general.... it acts as a vapour barrier.

but I wouldn't use it in a basement without a LOT of ventilation.

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