Confusing advice on mold removal
April 3, 2016 7:46 AM   Subscribe

Help us defeat mold on cinder block.

Our unpainted cinder-block basement wall has patches of black mold. It's not extensive -- about 2 to 3 times what's shown in this pic.
We understand the need to stop the moisture that's causing it, and we're taking steps to do that. But the advice we're seeing on actually removing/killing the mold is all over the map. E.g. use or don't use bleach, vinegar, etc etc.
We'll have a couple of pros come out this week for estimates, but we're also interested in DIY. So questions:
Assuming we can control the moisture level, is this mold something we can likely deal with ourselves?
And if so, what's the best method?
posted by SallyHitMeOntheHead to Home & Garden (9 answers total) 1 user marked this as a favorite
I am not an expert but there is a paint called Killz that I've often heard contractors mention using in these circumstances.
posted by kalessin at 7:59 AM on April 3, 2016 [1 favorite]

I've been dealing with the same conflicting advice and actually decided that really the substances that are made for this (sprays and foggers) are the way to go. My cinder block is painted our else I'd follow up the killing with a water seal like Drylok.
posted by soren_lorensen at 8:22 AM on April 3, 2016

OP here. The area with mold is in fact painted -- and that's the only place with mold. Here's another pic showing painted and unpainted.
It's a very small part of the basement -- and maybe it's not paint, but a sealant of some sort? That would indicate there has been problem there before.
Not sure if this impacts my original question.
posted by SallyHitMeOntheHead at 8:46 AM on April 3, 2016

Seconding kalessin's advice of looking into Killz. The house where I was living in college was in the middle of a flash flood one summer, leaving standing water nearly up to the ceiling of the unsealed cinderblock basement. After the water drained, my roomies and I were all sick for months from visible and invisible mold until the landlord came in and coated the whole place with Killz. We were all on the mend within a week or two. I pass containers of this stuff in the hardware store and am immediately awash in warm fuzzy feelings because it worked so well.

You might also consider a product called Drylok (DIY blog post).

The Killz was used in a semi-arid climate -- not sure if that makes a difference.
posted by mochapickle at 8:49 AM on April 3, 2016

This Zinsser page has many products that might work. This product looks good. I imagine the key to success for any of these products is to get the surface of the blocks clean and dry.
I would use bleach to get rid of the mold.
posted by H21 at 9:17 AM on April 3, 2016

For what it's worth, i had recurring black mold on the ceiling of a not-well-ventilated bathroom. I tried everything. Finally i just cleaned it really well then primed it with BIN shellac primer (the kind you thin with alcohol) and painted as normal and that seemed to kill the mold and keep it from coming back. i bought a clip-on fan as well to mitigate moisture. I'm not sure if i cleaned it with alcohol before priming but i did definitely thin the BIN with alcohol for ease of use, but also in the hope that the extra alcohol would help kill the mold. I applied more than one coat of primer(possibly three) before painting and the mold never came back (at least not in the four years i lived there).

It might be worth it to try a multi-pronged approach, solve the moisture issue, apply something to kill the mold, apply BIN and use a moldicide additive to whatever paint you use. You might even try a marine paint or epoxy based paint to seal-in any spores that are living in the porous cinder block. From the photos it looks like the mold is growing mostly on the painted surfaces where moisture can collect, as opposed to the raw cinder block that can probably breathe a bit. It might help to try any/or all of the above and then buy a fan to dry that area continuously for a while and see if that helps.
posted by Conrad-Casserole at 9:43 AM on April 3, 2016

You can't put Dryloc over an already-painted surface. I'd suggest a mold killer, then a coat of Killz, then put a dehumidifier in the area.
posted by soren_lorensen at 9:47 AM on April 3, 2016

This happens in moist areas. Hit it with some bleachy water and a scrub brush. It's not biohazard, it's time to clean.
posted by humboldt32 at 12:06 PM on April 3, 2016

Bleach and water mixed in a spray bottle. Spray, wait a few minutes, scrub, rinse. When it dries paint with Kilz.
posted by fixedgear at 1:06 PM on April 3, 2016

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