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How do we know if we should be redoing all the drywall (on exterior walls) in the basement or leave as-is?

We just moved into an older house (1970s) that was mostly sitting empty for about 6-12 months so everything does have a slightly musty smell to it and there was a leak in another part of the basement (since fixed).

There isn't clear evidence of mold, besides a few spots on the surface of the drywall in one of the basement rooms, but that could have been caused by something in the room that has since been removed.

When we cut an opening in the drywall we discovered that there is a layer of plastic, then insulation, and then plastic right against the cinder blocks. We are assuming that all the finished exterior walls have been done like this. We will be using the basement regularly for office space, laundry, and rec room and we aren't planning on moving in the next 30 years.

We are wondering what the risk is of just leaving everything as-is. My husband feels that if this was like this for years, then we can just leave it. I feel that since we know that plastic right up against cinder blocks is a recipe for mold, we should redo it all.

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The plastic will reduce the moisture, bare cinder block walls are almost always damp, there may be a drain tile at the base of the wall to take the moisture away, I would leave the plastic in place. I have rarely found dry cinder block basements so this will be something to watch. A dehumidifier will help dry things out and prevent mold growth. Making sure the gutters drain away from the home and the ground graded so any water drains away from the home will help to reduce chances of moisture making its way through the walls.

  • Thanks for the answer. We will definitely have to fix some of the grading, and we are already planning to replace the gutters. I do worry that the plastic will trap the moisture and not allow the cinder blocks to dry out... we do have a continuously running dehumidifier in the basement, but I don't see any sort of "drain tile" that you mention... what would that look like? – mag Jan 8 at 19:57
  • @mag Concrete is porous. Water will penetrate it. The plastic is to keep the moisture that's in the soil and makes its way through the block walls from entering the living space and rotting the wood and softening the drywall. The drain tile would be something like a French drain either outside the house, underneath the basement slab, or possibly (but not likely) both. – FreeMan Jan 8 at 21:38
  • Freeman is correct on the drain, on the house I had where we had to install inside there was only a 2" wide channel along the basement wall, I covered that wall the same way as your home but the bottom plate was cut away from the wall, I lived there for 4 years and we never had problems other than the high humidity. – Ed Beal Jan 8 at 22:19

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