Could the strange white powdery substance found on the concrete floor of our basement bedroom be mold, or could it be something else entirely?
Asked by Marija Rakić 
7 months ago
Last Updated: May 28, 2024
So, we were tearing out the carpet in the basement bedroom and we stumbled upon this strange white, powdery substance on the concrete floor. It doesn’t seem to be paint, carpet backing, or drywall dust, and it didn’t budge when we tried vacuuming it up. Could it be mold? Any other thoughts on what it might be?
You might notice mineral deposits from moisture. It’s commonly visible when water or dampness penetrates concrete.
Blooming
If you want to learn more about efflorescence, check out this link: https://www.nitterhousemasonry.com/blog/what-is-efflorescence/
Try using a wire brush and/or CLR.
White mould has a very strong smell. It’s a combination of dust, dirt, and efflorescence. Just make sure to clean it up properly.
Then addressed the moisture issue that led to the efflorescence.
Efflorescence is actually caused by moisture that is present in the concrete but not visible to the naked eye.
It’s the lime and sodium chloride seeping out of the solid concrete
& , you guys are spot on. Efflorescence comes in two forms – primary and secondary. Both occur due to moisture evaporating and pushing minerals to the surface. The big question is whether the moisture was present in the material during manufacturing (primary) or if it seeped in after installation (secondary)
It seems to have some old carpet tack strips. There is efflorescence surrounding them. My guess is the moisture is seeping up from underneath, or possibly the walls connecting to the concrete floor are letting in water from the outside. The reason I’m leaning away from condensation is because of the significant amount of moisture present. The wetness is noticeable on the floor in front of the tack strip. If it was condensation from the walls, most of the wetness would be behind the tack strip
Oh, it’s blooming. It’s essentially salts and minerals in the concrete that have surfaced due to moisture evaporating out of it. It’s harmless, but could signal a moisture problem.
Just bag it and try selling it on the streets like meth in a town you’re not even familiar with, haha
Just regular concrete salt, nothing out of the ordinary
Totally fine, nothing to stress about!
Seems like boric acid. People used to use that to keep roaches away.