Dry Out a Moist or Humid Basement
LESLIE: Shirley in Michigan’s got a lot of basement questions. What can we sort out for you?
SHIRLEY: Yes, I have a farmhouse that was built in the 1800s.
SHIRLEY: And it’s called a Michigan basement; a half dirt and half cement floor.
LESLIE: Oh well, here we call them Yankee basements.
TOM: Yeah. (chuckling)
SHIRLEY: Oh, OK. And we have these huge stones for the foundation; you know, the side walls of the basement.
TOM: (overlapping voices) Right. Mm-hmm.
SHIRLEY: And the windows are shut, you know, just all year round. And we have no water problem because we have gravel soil. But the basement is so damp and I think the more – you know, we’ve been here more than 50 years and it just seems like it’s getting more damp. And I was wondering about the radon.
TOM: Well certainly radon gas is something that you should test for. It’s very inexpensive. It’s caused by the decay of uranium in the soil.
LESLIE: But does dampness have an effect on the occurrence of radon?
TOM: No, it’s totally disconnected. They’re really two issues.
SHIRLEY: Oh, I see.
TOM: So let’s just address the radon first. It has nothing to do with the humidity. It’s the decay of uranium in the soil. And so you need to test for that. You can order online a charcoal absorption canister, which looks like about the size of a can of tuna fish. And you simply open it up and you leave it in your basement usually from two or three to seven days and you seal it back up and you send it to the lab. And you record the start time and date, stop time and date. You send it to a lab and then they’ll actually read it and tell you what the level is. It’s going to come back in – with a measure of picocuries. That’s how radon gas is measured. And if it’s 4.0 picocuries or higher, then you would want to do some follow-up testing and perhaps install a mitigation system. If it’s below that, it’s considered to be safe. So that’s the first thing you should do is check that.
In terms of the humidity – the moisture – lots of things could be causing that, Leslie. I’d start outside.
LESLIE: Yeah, you want to look at a few things around your house. Definitely look at your gutter situation. Do you have gutters on the house?
LESLIE: You don’t. (chuckling) Well that could be a huge part of this.
TOM: (overlapping voices) Yeah, big mistake.
LESLIE: Because as the rain drips off your roof, it’s just going directly down to the side of your foundation. There’s nothing there to collect it and direct it away from the house. So that’s putting a lot of moisture into your basement. So get some good – a gutter system put onto your house and when they put the downspouts on, have them make those downspouts deposit the water as far away from the foundation as you can. If you’re going to put them above the ground – three feet, six feet, fine. If you can, bury them and direct them as far away from the house as you can. And that’s going to make a huge difference.
And then, you also want to look at the grading around your house. You want to make sure that all of the dirt slopes away from the foundation. And we’re not talking drastically. We’re talking about four inches over six feet. So it’s a gradual decline away from the house. But that does enough to get that moisture away.
And those two things should be really effective.
SHIRLEY: Would it be a good idea to put cement in that path that’s dirt?
TOM: No. No. You can control this by managing the water, Shirley, and keeping it away from the house. So the gutter system is going to make a huge difference. That by itself is going to dramatically change the amount of humidity you feel in that basement, guaranteed.
SHIRLEY: OK, because this house has never had them.
TOM: No, I know that. And you really do need to have them. Because the water is saturating the foundation perimeter and it’s weeping through those foundation walls and it’s evaporating into the air and that’s why you feel so clammy. So that’s why you need to get the gutters on.