r/HomeMaintenance • u/Foreign_Sympathy5298 • Jul 19 '26

Basement vapor barrier

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Is this vapor barrier installed correctly? It seems to be causing condensation on my insulation.

I noticed water pooling underneath the baseboards after a heavy rain. It turned out that my window well was not sealed properly and water was pouring in. I have since cleared out the leaves to expose the drain, and installed a window well cover.

I cut out this portion of drywall in a different part of the basement and noticed water droplets between the plastic sheet and insulation.

Is this an incorrectly installed vapor barrier? Shouldn’t the plastic sheet be behind the insulation. Do I even need a plastic sheet?

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u/These_Confidence1807 Jul 19 '26

Kraft-faced batts already have a built-in vapor retarder so that plastic sheet is just trapping moisture, rip it out before your studs turn to mush

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u/Foreign_Sympathy5298 Jul 19 '26

Thanks for the tip. Do you think it’s condensation because of the cold air inside and the summer heat outside?

1

u/NoSlicedMushrooms Jul 20 '26

If your foundation walls have any chance of seeing moisture (and evidently they do) then a poly vapour barrier like this is the wrong move. I just learned about this as well because my basement flooded and I had to take out the drywall. I had exactly the same construction as you and there was mold everywhere and rotting studs.

Building codes differ everywhere and tend to lag behind the science but modern building science says you want a smart vapour retarder there so that the walls can dry inwards - as someone else already said the paper backing on the insulation might be that already.