Cleaning Concrete Floor Discoloration

Learn why concrete floor discoloration is likely due to mineral-salt deposits rather than mold or mildew. Find out how to remove the deposits using a vinegar-and-water solution. Get tips on sealing the concrete using an epoxy paint to prevent moisture…

[mai_avatar size="40" margin_right="-4px"][post_author_posts_link before=" by "][post_date before=" — "][mai_icon icon="comment-alt-lines" style="light" display="inline-block" size="1em" margin_left="12px" margin_right="-8px" margin_bottom="-4px"][post_comments][post_sponsor][shared_counts]

LESLIE: Pat in Louisiana is on the line and needs some help with cleaning concrete floor discoloration. What can we do for you?

PAT: We had our carpet cleaned about a year ago. And in this bedroom, we have a heavy, clear, plastic mat that goes underneath the computer chair.

TOM: OK.

PAT: Well, recently, I moved it over a bit and I noticed that it was wet underneath it.

TOM: OK.

PAT: There’s no leak in the roof; water hasn’t come in the house. So only thing that could be is a year ago, the water from the carpet-cleaning service got underneath this mat and it’s been there all this time.

TOM: Hmm. OK.

PAT: So, we cut out a large circle, like a 5-foot circle, and got all the part out that was wet. So we’re going to have to replace the carpet and the pad. But on the concrete – the bare concrete – there are some spots of discoloration, so I don’t know if that’s mold or mildew. My question is: how do I clean that concrete before we have the new carpet installed?

TOM: The concrete floor discoloration, if anything, are mineral-salt deposits; it’s not mold.

PAT: OK.

TOM: And so, it’s really cosmetic at this point. If you can wash it down with a vinegar-and-water solution, it’ll melt the mineral-salt deposits away.

But the other thing that occurs to me is sometimes, concrete will draw moisture into a house. And so if anywhere near that area outside, you’ve got water that’s ponding or collecting, it’s possible for the concrete to sort of draw that moisture up into the slab and across. And it may not have been able to evaporate where the pad was covering the concrete, which is why that area stayed damp, whereas the other area dried out. So there may be a different explanation as to why that stayed wet.

One of the things that you might want to do for concrete floor discoloration, since you have the carpet pulled all the way back, is to paint the concrete. Paint that area with an epoxy paint. That will seal in that concrete and stop some of the evaporation if the moisture is being drawn through it and up into the floor surface.

PAT: So, should I – we paint the whole room? We don’t have all of the carpet up yet; we just cut out the middle part.

TOM: Well, if you’re going to take all the carpet up, then paint the whole floor. If you’re only going to take part of it up, then just paint what you can get to. But I would definitely paint the floor.

PAT: OK.

TOM: That’ll do it. Pat, thanks so much for calling us at 888-MONEY-PIT.