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White Powder on Basement Walls

  • Transcript

    LESLIE: Debbie in Delaware, you’ve got The Money Pit. How can we help you today?

    DEBBIE: I have a home built in 2006. I have an unfinished basement. All the walls are cement. My air conditioning and heating unit is down there.

    TOM: OK.

    DEBBIE: I have a very fine, white – it’s not even a dust; it’s like a powder that’s getting through the whole house.

    TOM: Through the whole house.

    DEBBIE: It’s going through the whole house. It’s got to be coming through the heating and air-conditioning vent.

    TOM: OK. Hmm.

    DEBBIE: I don’t know if it’s something – it feels like the same powder that is on the cement walls. Like something was sprayed onto them?

    TOM: So are – these are concrete-block walls?

    DEBBIE: Solid concrete.

    TOM: Solid concrete. Alright. And do you see any sort of white powder that’s sticking to the concrete – to the cement wall?

    DEBBIE: Absolutely.

    TOM: You do? OK.

    DEBBIE: Yes, absolutely.

    TOM: So …

    DEBBIE: Like if I go to wipe my finger on and it’s in this chalkboard?

    TOM: Yep, OK. So here’s what’s going on. And it may be – it may not be connected, these two observations. But in so far as the walls are concerned, that’s a mineral-salt deposit. And what happens is the water that collects around the outside of your foundation will draw into the wall. The walls are very absorptive. And it will draw into the wall and it will evaporate – the moisture will evaporate – into your basement but it will leave behind the mineral-salt deposits that are in the soil and in the water.


    TOM: And that’s that white powder. Sometimes it looks light gray. And you can prove it to yourself just by taking a little bit of vinegar and wiping down the wall. Usually, vinegar will melt salts and makes it disappear.


    TOM: Now, it’s nothing harmful about it but it does indicate that you have too much moisture collecting around your foundation perimeter, Debbie, so I do want you to take a look out there and make sure that the soil is sloped to grade away from the walls. Also, make sure that your gutters are clean and free-flowing and that you’re not doing anything to really retain water at the foundation perimeter.

    In the worst-case scenario, this kind of situation can develop into a wet basement. And so we don’t want it to get that far for you.

    DEBBIE: No. Could that be getting into the air conditioning and the heating unit?

    TOM: Doubtful. I think you’re seeing some other type of dust that’s getting into the HVAC system, so let’s talk about what to do with that.

    Now, in most cases with homes that were built and – you said 2006. In that era, most of the heating systems are going to have a fiberglass filter in them. Now, do you know where your filter is for your air conditioner and heating …?

    DEBBIE: I do.

    TOM: OK. Is it in the blower compartment?

    DEBBIE: Yes.

    TOM: OK. So, typically, if you look in there, you’ve got a very thin, fiberglass filter. Those are not very effective filters; they just don’t do a great job.

    DEBBIE: That’s the one that I change?

    TOM: Yeah, the one that you change. Exactly.


    TOM: Now, what you could do is you could get a better-quality filter for that same space.

    DEBBIE: I change them like every month.

    TOM: Yeah, I know. And the thing is, you shouldn’t have to. You have to change them every month because they are not very good filters.


    TOM: And they clog up easily and they let a lot of stuff through. And we call them “rock stoppers,” because it’s pretty much all they stop.

    So, what you might want to do is get a – first of all, you can get a better-quality filter for that blower compartment. And if you look for one that’s pleated, that’s a good start. 3M has a line of filters that are pretty efficient. They’re going to have a MERV rating on them – M-E-R-V.

    Now, when you look at the MERV number, keep in mind that the higher the number, the better.


    TOM: So, a MERV 8 is better than a MERV 5. And a MERV 12 is better than a MERV 8. And so the higher the MERV number, the more efficient the filter system.

    Now, if you want to step it up from there and really put a much better-quality air-cleaning system onto the house, then you may look to an electronic air cleaner or an electrostatic air cleaner. And these would require a slight modification of your ducts. With the electronic air cleaner, it fits basically somewhere in the return side. And it’s about 3 inches wide and it uses a combination of static electricity and a filter to pull absolutely all the dust out. Now we’re talking about a filter that can take out minute-sized particles of dust and air and even virus-sized particles.

    DEBBIE: OK. Thank you very much.

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

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