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Basement Wall Condensation

Alex9999999 | Posted in General Questions on

I am a small contractor, i.e. handyman. A customer with an old house here in Western Mass. has a dirt floor basement with several gaps in the concrete wall where old windows or doors must have been. They are covered with plywood in some cases, exposed wood sheathing (beneath the exterior vinyl siding) in others. These were all quite wet when I visited recently, and she wants that addressed.

I’m thinking warm, somewhat damp air from the heated house is leaking through the subfloor (there is no insulation in the basement at all) and condensing on the wood, because they are the coldest surface. Correct?

How should I deal with this? It seems easy enough to cover them with rigid foam, with spray foam around the edges…will that prevent the water vapor from reaching those cold wood surfaces, and thus keep them dry? Or will the water vapor sneak around or through the foam.

The customer thought ventilating the basement would be the answer. To me this sounds like a bad idea, though it’s difficult to say why. 

Thanks for any suggestions, 

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  1. logicalIthink | | #1

    Hi Alex, Sound like you got a complex problem going there. The dirt floor is one culprit, the ply on the windows that is un-insulated is another, and there must be exposed cold water pipes and such that also provide additional surface for condensation. Making the old window openings water proof would be my first move, then creating a moisture barrier on the dirt floor would be next. Make sure there is proper grading so that snow and rain water flows away from exterior walls/basement is important as well (gutter down spouts included). Have seen an older home that would get a wading pool inside after every major rain and in the spring during the thaw. I had dirt floor, ancient foundation walls that served as basement walls, leaked like a crazy. Graded outside, dug a hole for a sump pump and covered the floor with thick plastic sheet, allowed some warm dry forced air heat to get down there and all was fine. It became so nice, a concrete floor was poured and the foundation/basement walls were cemented! Just thought I'd share my thoughts.

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