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We moved in to a house two years ago that had a crawl space dug out and turned into an unfinished basement area several years prior (>10?). I was hoping to turn it into a home brewing room (planning on using a steam condenser mounted on my brew equipment to mitigate any steam), so I got the floor polyaspartic coated. A friend came over and recommended that I seal the surrounding cinder blocks/concrete - but I noticed dark areas around several parts of the blocks. Drylok recommends removing efflorescence - which I think there is a little bit of, but I'm not sure what to do with the darker areas.

Prior to getting the floor coated, I've never seen standing water in the area. When I was prepping to get the floor done, I moved a poster leaning against the blocks and noticed a 1" x ~3" patch of minor mold that was on the back of the cardboard backer of the poster (which has been leaning against the wall since we moved in). Temp/Humidity:

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TL;DR - should I (and how) would you guys prep to seal the cinder block area?

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Whole "crawl space" enter image description here

isherwood
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pete
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1 Answers1

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Any cold surface will always act as a duhumidifier. If you have dust on that surface you have food and water which is perfect for mold.

Before you do anything with is your RH in the area?

It seems like you have a cinder block wall on the interior of your possibly poured concrete foundation? Did they do interior perimeter drain, do you have a sump? Are in you in a primary heating or cooling climate?

TLDR; get a dehumidifier. Sealing from the inside is very unideal but can be done. JLC had an article with an old converted wind mill with a stream running through the basement.

Fresh Codemonger
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  • I'm in Colorado - so its a drier climate, but I recently put two hygrometers in the room a few months ago - one showed it was 50% RH in the summer months and recently dropped to around 35% (update original post w/ plots). The other was consistently the same temp, but 5% lower RH. There's a sump pump on the opposite side of the house, although the converted crawl space is 2ft higher than the whole basement. There's no drain in the converted crawl space area, although 10 ft from the entrance is the HVAC/boiler room with a drain there. I believe the foundation is poured concrete – pete Nov 09 '23 at 04:10
  • ok that's fairly low RH. do you have thermal camera or laser temp gun to see what temp of the dark areas are vs the lighter areas? – Fresh Codemonger Nov 09 '23 at 05:22
  • is the water drop just humidity or relative humidity? what is the temp w the drop icon? – Fresh Codemonger Nov 09 '23 at 05:36
  • You shouldn't be asking questions in your answer. Do that in comments on the question post _before_ you answer. – isherwood Nov 09 '23 at 14:22
  • I have a laser gun temp - i'll try to get some data tonight. The drop is relative humidity, drop + temp is dew point. – pete Nov 09 '23 at 16:54
  • no difference in temp between dark vs light – pete Nov 10 '23 at 20:25