Best way to kill mold on wall before painting?

decagonMay 19, 2009

Hello everyone,

I'm a complete novice at painting and plan to paint my house interiors myself for the first time. I took down some wallpaper in a bathroom and a few days later some mold started growing in a small area. We had it professionally tested and luckily it was benign (Cladosporium and Penicillium). It's spreading a bit and I want to kill it in a manner that will prevent it from coming back before priming and painting. The bathroom has lathe and plaster walls, although we're patching some areas with new drywall.

I went to Home Depot and a paint dept employee told me to paint over it to "seal the mold in" because the paint chemicals would kill it. This does not sound correct to me. I'm thinking I should apply something topically to kill it before painting. I was going to use bleach but was warned that it isn't effective against mold on porous surfaces like walls.

I would appreciate any suggestions anyone could give on how to get rid of the wall mold permanently before priming and painting.

Many thanks,


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Christopher Nelson Wallcovering and Painting

Bleach, etc. will not penetrate the drywall and will only kill the mold spores on the surface. The remaining spores can remain dormant inside the drywall until the next time when enough moisture exists for a "bloom". So, in addition to moisture control, a good priming with a pigmented shellac will block the mold spores into the drywall and reduce the likelihood of future damage.
This was taken directly from another site.Moisture control is essential.

    Bookmark   May 19, 2009 at 4:44AM
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Thanks for the information! I live on the ocean and we've been having muggy, overcast days. I think that was enough moisture to make the first mold bloom because the bathroom wasn't being used so there wasn't another moisture source. If outside humidity is enough, then it will be almost impossible to keep dry enough to prevent reblooming from spores in the wall. If they're in the wall, and paint/shellac is on top of them, can they bloom on the inside of the wall and spread into the framing?

    Bookmark   May 19, 2009 at 1:51PM
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Personally I think the health hazards of most common molds are overblown. Having said that, HD sells a mildewcide additive for paint that I have had very good luck with. M-1 made by Jomax. The mold may be growing in some residual wallpaper glue on the wall. Make sure all the paste is removed before painting or you're asking for problems very shortly after painting.

The HD employee that told you the paint had chemicals in it that would kill mildew was being a little "optomistic" I think.

    Bookmark   May 19, 2009 at 8:14PM
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Thanks for the advice about Jomax's M-1 product. Our local HD doesn't carry it, so I'll check around for it elsewhere. The suggestion that the mold is in the old wallpaper paste residue rather than the wall is hopeful. I cleaned the wall after taking off the wallpaper, but maybe some residue is still there. Which is the best product for cleaning off all old paste?

    Bookmark   May 20, 2009 at 2:38PM
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Most hardware stores will carry a liquid walpaper stripper but you propably don't need it. I would use a qt. spray bottle to moisten the wall, wait 5 min, then use a synthtic sponge and a bucket of water to take off the residue. The sponge I use is commonly called a grout sponge and scrubs well, won't clog up with paste residue, but doesn't hold water well. A wet wall will be slick, but one with paste on it will feel slimy. Scrub, rinse, feel for residue, move on. Wet the wall ahead of where you are currently scrubbing so the paste can soften and don't scrub through the paint/primer. Wallpaper paste is basically wheat paste. Be careful around the drywall patches and joint compound as water will dissolve un-primed joint mud.

    Bookmark   May 20, 2009 at 8:36PM
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Thank you very much for the detailed advice on paste removal. I'm going to the hardware stores around me tonight to look for all the material everyone suggested and I'm dedicating this weekend to resolving this problem.

Again, I really appreciate everyone's suggestions. You've all been very helpful.

    Bookmark   May 21, 2009 at 5:47PM
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