I have a basement that I am planning on finishing. There was a mold problem. After washing the basement walls, I soaked them in Concrobium. I then painted the walls with a masonry waterproofing paint that's antimicrobial. Two days later, I see brown mold stains coming through the paint. Is the mold still living? What can I do here?

  • Are the walls masonry or drywall? Mar 9, 2015 at 17:34
  • It doesn't sound like mold. Mold won't grow through the paint in two days. It may be new mold on top of the paint but the antimicrobial additive should be preventing that. May be some type of efflorescence but the masonry waterproofing paint should prevent that. If you have cleaned all the mold off the walls as you indicated there shouldn't be anything to bleed through. Might want to do a mold test to see if it is mold or not and post some close up pictures. By the way, what did you wash the walls with? Mar 9, 2015 at 17:56
  • I used Concrobium House and Deck Wash. And then I soaked them in Concrobium Mold Control. And then I painted two coats of Seal-Krete waterproofing masonry paint, which is very thick stuff. I noticed with painting, there were a few brown spots that just came right through the paint immediately. Other spots have appeared 24 hours later. The basement is dry. The walls were bone dry. There's plenty of ventilation.
    – Chris
    Mar 9, 2015 at 18:24
  • The walls weren't mold free. The foundation walls probably have a bit of water in them. You have now sealed the water in and enclosed the mold which is a perfect growth multiple. You need to really clean the mold perfectly. The paint is something I would never suggest in your case.
    – DMoore
    Mar 9, 2015 at 18:59
  • If you ask me the most relevant question is do you have water proofing layer under your floor and behind your walls? Also I'm 99% sure that mold wasn't removed completely. Mar 27, 2015 at 8:37

1 Answer 1


I have never used Concrobium. I have cleaned foundation walls with hot water and bleach. Now that you have painted you have added something else into the mix. The paint can actually harbor the mold. I would simply get a heavy bleach and hot water solution with some heavy duty metal brushes and scrub the crap out of the whole area. The paint probably has to go. Make sure you have gloves on, goggles, and a mask.

Fan the area out for 2-3 days. You need to wait a minimum of 2-3 weeks and possibly a few months before I would even think about drywalling.

I would really try to get at the source though. Even if mold is growing it needs food. It wouldn't have returned that back unless your basement was feeding it water. If you don't take care of the moisture issue first you will keep fixing a mold problem.

  • Thanks for the feedback. I haven't installed the drywall yet. I'm just talking about the foundation walls. I painted the concrete walls after treating them with Concrobium and the mold is showing through two days after I painted them. I'm surprised because I really doused the walls with Concrobium. They were bone dry when I painted. I want to deal with this before I do all the framing and drywall work.
    – Chris
    Mar 9, 2015 at 17:41
  • +1 for pointing out the source of the problem seems to be moisture. Even if it is not mold but something else leeching through, moisture could very well be a decisive factor.
    Jun 7, 2015 at 14:41

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