Expert: Dan Griffin - 9/23/2008

Question
Hello,
My NY home is a 4 yr old modular on a full concrete basement. The first year or two, I painted the walls with Drylock waterproofer and the floor with Drylock paint. The walls didn't really seal because all the little concrete holes show through, but I'm sure it helped. I also put up 4 mil plastic from floor joist to basement floor and planned to construct over that so as to have a moisture barrier. One part of the back wall developed a crack top to bottom, hairline, and leaked some water after raining. I'd get a puddle of a few feet. Once we got gutters installed this past month, the leaking ceased and was only a spot of moist looking concrete. I plan to cover that up and continue with the finishing. What is the proper way to finish off a basement with regards to building walls? I've seen shows where they stud the walls then plastic on the inside, but then people who know carpentry tell me to plastic next to the concrete wall. I'd just like to know the proper way to do this so I don't have a moisture and mold problem somwhere down the road. Thank you.

Answer
Mike, finishing basements is problematic.  I beleive in planning on when the basement leaks, not if.  You already know that your basement takes on some moisture.  It would be best to solve the moisture trouble before finishing the basdement.  I believe in a layer of vapor barrier, plastic, against the concrete sealed at the top to keep moisture from getting to the  studs or wall materials.  If possible, direct the bottom of the vapor barrier to a sump drain.  I like a treated bottom plate with gaps to allow water out and air circulation between the concrete wall and the stud wall.  I prefer metal studs.  A dehumidifier would be essential to the comfort of the basement.  Avoid a double bapor barrier by using insulation with no facing material.  Consider using one of the new mold proof drywall products.