Expert: Bruce E. Johnson - 3/30/2009

Question
QUESTION: Plan to finish basement.Block foundation(gets wet in a few spots)Using metal studs and mold/moisture resist rock. Have french drain w/ 2 pumps. Should I seal block wall first? Also, do I need a vapor barrier on back side of studs? A contractor recommended a sealer paint that has an almost rubber consistency. What do you think? Thanks, Jim

ANSWER: Hi Jim, yes you need to seal the block.  The rubber mastic is a good way to go. There is a cementious product called Dry-Lok that is another way to go but either the rubber or the drylok will work.  Also the exterior of the wall should have been sealed and you need to make sure your drain is working properly...I hope this information helps, feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com

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QUESTION: Do I need a vapor barrier? 3/4 of the basement will be finished. I plan to leave a 3-4 inch gap between block and studs for some air flow behind the walls. Also will be using a de-humidifier and try to tap into my forced air HVAC. Should I install additional open vents for more air flow behind walls? Thanks again, Jim

Answer
Hi again Jim, a good sealer/ mastic on the walls would be the vapor barrier.   I suppose if there is a moisture problem you are worried about you could put some wall vents in the stud walls one at the bottom one at the top(air moves in a circle bottom to top)..These transfer grills don't need to be big, maybe 4x6 tops (there are all sizes) and only a couple per wall unless you know of one wall with more moisture problems than the others. But as far as vinyl vapor barriers behind the studs?  as long as you have sealed the wall decently then you are fine....I hope this information helps, feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com