How to Paint Basement Walls

LESLIE: And now a painting question from Rosie in Iowa.

Rosie, what are you painting?

LESLIE: OK, and what are the walls made out of?

ROSIE: Cement block.

TOM: Now are you dealing with a water problem, Rosie? Is that why you’re painting them?

ROSIE: Yes.

TOM: Alright. Well, here’s what you need to do. So is your question what kind of paint to use or what?

ROSIE: No, I have the paint but the label on the can is gone and it needs to have some thickening – I mean thinning – and I don’t know what to use for a thinner.

TOM: OK. Do you know if it’s water-based or oil-based?

ROSIE: I don’t know. The label, most of it, is gone for the directions.

LESLIE: Rosie, when you opened it up, was there like a thin layer of something clear on top of it? Did it seem to separate?

ROSIE: It seemed to be thick and there was very little liquid on top.

TOM: Rosie, is this old paint?

ROSIE: I think so.

TOM: OK, well I would recommend you not use it. If you’re – you need to buy some new paint.

ROSIE: Oh.

TOM: OK? Let’s back up for a second though, Rosie. You’re obviously dealing with a moisture problem in that basement. Is that why you want to seal those walls?

ROSIE: I do.

TOM: OK, so here’s what I want you to do. Before you paint the walls – we may be able to fix this without the paint. We need to identify the source of the moisture. Typically, Rosie, what happens is if your gutter system is clogged or if your downspouts are not extended away from the house or if the soil around your house is too flat or slopes into it, that’s why you get leaky basement walls. So the first thing you want to do is have someone check your gutters to make sure they’re clean and free-flowing and getting that water away from the house and the next thing is to adjust the grading around the side so that it slopes away. Those two things cure a whole bunch of leaky basement wall problems.

Now if you do those two things and then you still find that you’re having some leaks, what I want you to do is to go out and buy some basement water seal paint. Thompson’s is a very well-known brand for that; Thompson’s WaterSeal. It is a thicker paint and it’s really designed to stop that surface moisture from getting through. But if you put that on and you have not done anything to correct the gutter problem or a grading problem, the water is just going to keep coming at you, Rosie, so you really need to look outside and try to slow down the source of that first and then you go ahead and put on the paint inside. Do you understand?

ROSIE: Well, how can you tell whether it’s water-based or oil-based?

TOM: Well, if you’re going to buy new paint, you don’t have to worry about it because it sounds like the stuff that you’ve got is pretty old. But here’s one trick of the trade. If you open it up and you see oil floating on top, then it’s oil-based. If it just looks like it’s sort of crusted over, most likely it is latex-based.

Would you agree, Leslie?

LESLIE: I would.

ROSIE: Well, OK then. Thanks.

TOM: Alright, Rosie. Thanks so much for calling us at 1-888-MONEY-PIT.