Waterproofing Finish is Flaking Off the Basement Walls

LESLIE: Sean in Ohio is on the line and needs some help with a moist basement. Tell us what’s going on.

SEAN: Yes. My basement, I finally got the outside fixed. I heard you guys say if it’s a rain event, that’s usually drainage. So I got that done and now there’s some kind of ceramic – or some waterproofing on the walls and it is flaking off onto the floor.

TOM: Oh, great.

SEAN: And it’s been there – the house was built in the 70s and I was wondering a good way to clean that up or what I could put on the walls to re-waterproof it.

TOM: OK. So, I think what you’re talking about are mineral-salt deposits. Is it sort of like a whitish, grayish, powdery substance?

SEAN: Yeah, yeah. This is like it’s been spackled on, though.

TOM: Oh. So somebody put something on the walls and it’s releasing and falling off the block?

SEAN: Right.

TOM: Hmm. OK. What do you plan to do with these walls?

SEAN: I just want to just waterproof them again, get the mold off of them and clean them up.

TOM: So, I don’t know that you have mold on the walls. It sounds to me like you’ve got some sort of a finish that’s separating. So, can you scrape it off? Will it release easily?

SEAN: Yeah, yeah. I just didn’t know, being the 70s, whether it might have asbestos in it or is there a good – better way to clean it up?

TOM: I would say not likely. Of course, you could have that tested, too. But if it’s coming off easily, I would remove it and if I put anything on the walls at all, it would simply be a damp-proofing material, like a Thompson’s WaterSeal.

And remember, the purpose of that is not to waterproof your walls; it’s to slow down the evaporation of moisture from the soil outside into the walls and any mineral salts that will be drawn through because of that. You’re not going to waterproof simply by painting your walls; it just doesn’t happen that way. You waterproof by redirecting the water away from the house, which it sounds like you’ve already tackled on the outside.

SEAN: Yeah. It took me about 15 years but I finally got it done.

TOM: Yeah. If it scrapes off easily, I would continue to take the rest of it off. I’d clean it up, I’d put a couple of coats of damp-proofing paint on it and I’d call it a day.

SEAN: Oh, OK. Well, thank you very much.

TOM: You’re welcome. Good luck with that project. Thanks so much for calling us at 888-MONEY-PIT.