I just had a basement waterproofing job done and it is doing an awesome job relieving pressure and keeping the basement flood-free (we just had a very large amount of rain here in central PA and it was dry as a bone down there). The problem is, it is still very moist. We are talkin' 85% humidity. I used my moisture meter and the culprit is definitely the walls.

I am thinking of installing insulation board over the whole basement, as I have heard this will act as a moisture barrier. My concern is, there is still old drylok paint on the walls, and we just got the walls acid washed to get rid of the mold. Do I need to remove the paint before putting up the insulation board? Can I instead paint over it with a non-mold friendly paint first?? Will that be ok?

Also, I am open to hear other solutions for basement moisture issues.

  • You say you’re “open to hear other solutions for basement moisture issues.” I thought you said it’s “dry as a bone”. Do you mean it’s humid? Have you tried a dehumidifier? – Lee Sam Aug 27 '18 at 3:24
  • When I said "dry as a bone," I meant no liquid water. Sorry, probably not the best words to use! Yes we have a dehumidifier but it isn't big enough for the basement (we need another) and a dehumidifier isn't a good solution to the problem IMO. I would rather stop the moisture from getting in all together, rather than deal with it once it's in. – user41178 Aug 27 '18 at 12:10
  • Where do you expect the moisture to go? Or in other words, what is your definition of "in"? – Harper - Reinstate Monica Aug 27 '18 at 13:23
  • I am under the impression that the foam insulation keeps the moisture from escaping the block faces and entering the basement. I am just trying to figure out if I have any other choice than to excavate the outside and install a barrier out there. – user41178 Aug 29 '18 at 1:45

If the humidity in the basement is high, it will condense on the cold or cool basement walls causing them to feel damp or even sweat. You need to reduce the relative humidity in the basement and probably in the whole house. If you air-condition your house as I do, you need to find out the relative humidity in the house. If it is above 40% you should buy a dehumidifier, probably a 50 pint/day or larger, to reduce the humidity. You said that you live in central Pa. I live 30 miles north of Pittsburgh so I know your climate. I run my A/C at 75 degrees, have a finished basement, and run a dehumidifier in the basement. Hope this helps.

  • Our house only has window unit AC, and no AC in basement. We don't run the AC during the day and the upstairs humidity is also quite high around 60%. Meaning the humidity in the basement in about 25% higher. I would like to stop the moisture from infiltrating at the source, rather than deal with it once its in with AC. I was under the impression that the insulation board would act as a moisture barrier and help. I just wanted to post here to find out for sure since the insulation board is expensive. – user41178 Aug 27 '18 at 12:14
  • You must get the humidity down to 40-50% or you will always have moisture issues. If a 70 pint/day dehumidifier is unable to maintain that level, then I would suspect there is water present in the wall leaking in from the exterior. – peinal Sep 27 '19 at 16:14

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