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Dry Out a Damp Crawlspace

  • Transcript

    LESLIE: Next up, from California, is Kevin, who finds The Money Pit on the QUAKE. And you’ve got a crawlspace situation. What’s going on?

    KEVIN: Well, I’ve … I noticed that there’s a … a kind of a dampness under the crawlspace that doesn’t go away during the year. The house does have downspouts. I’ve listened to your show many times and I know the first question is (chuckling), “Are there downspouts?” So, yeah, it does have downspouts. And … but the crawlspace just seems moist. And so like, where I pick up some whiffs of … through the vents and stuff that are under the house, whatever, I can occasionally smell some of that wetness.

    TOM: OK.

    KEVIN: Yeah, that wet smell that kind of comes up from underneath the house. And I’m just wondering what I should.

    TOM: Alright. A couple of things, Kevin. Of course, you know, from listening to the show, that we always recommend good grading and drainage so that’s making sure the soil’s sloping away from the walls and the downspouts are extended out away from house. You got that covered. So let’s look inside the crawlspace. Do you have a vapor barrier down across the surface of the floor?

    KEVIN: No, that’s one of the things I was thinking about putting down.

    TOM: Yeah, I would … I would put a vapor barrier down. You want to put that down with as few seams as possible across the entire dirt surface of the floor. And then, if the moisture continues, there’s one other thing that you can do and that is that you could put a ventilation fan in that crawlspace. Mount it in the crawlspace vents, in the foundation wall. And have that wired to a humidistat so it only comes on when it gets super damp in the crawlspace and helps pull some dry air across the floor and evaporate any remaining moisture. But all of those things working together should do a good job of slowing down that humidity.

    KEVIN: So if I put the vapor barrier down and it’s still a little moist underneath that …

    TOM: I wouldn’t worry too much about that.

    KEVIN: OK, OK, great.

    TOM: That’s OK. You know, I’ve crawled through crawlspaces on vapor barrier and had puddles of water underneath and I don’t get too worried about that, as long as it’s not a lot. Because what that vapor barrier’s doing is it’s basically stopping that vapor from evaporating up into the crawlspace air zone and potentially causing mold and rot to form on the floor joist or getting the insulation wet, which makes it very ineffective. So that’s the purpose of the vapor barrier. If you get a little water underneath it, I wouldn’t sweat it.

    KEVIN: OK, great. Yeah, because there’s no pooling of water. It’s just moist.

    TOM: Yeah, that’s not so bad, Kevin. I think you’re going to be OK with a vapor barrier.

    KEVIN: Great. Well, thanks. I love you guys’ show. It’s really a lot of fun to listen to.

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

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