Eliminate Moisture in a Crawlspace
LESLIE: Greg in Missouri is having a situation with mold in the bathroom. How can we help you?
GREG: Yeah. I’ve got an older home with a crawlspace under it.
GREG: And I keep putting down new linoleum in the bathrooms and the linoleum grays at the edge.
GREG: And I’ve talked to several people and they suggested a vapor barrier under the home and I was just curious as to which way to go to create a vapor barrier. Some people say tar paper and then white rock on top. Some people say plastic and white rock; some people say foamboard.
TOM: Now, what you want – what you want here, Greg, is you want to use plastic and you want to use as wide a sheet as possible. You want to go all the way from edge to edge of the foundation. If you can, turn that up the inside foundation wall by about a foot and try to get it to seal against the wall. You could use caulking or you could use like an asphalt roof cement so you have a real tight seal against the wall.
When it comes to overlapping the sheets of plastic, I would overlap them a good two or three feet. You know, plastic is pretty cheap so you don’t have to worry about using a little more or a little less. And the other thing, though, is to look at the overall reasons that the moisture is getting into the crawlspace and for that, what I would do is look at the grading at the outside of the foundation; making sure the soil slopes away from your walls.
And also, don’t forget to check your gutters. You want to make sure that they’re clear and free-flowing so that that water from the roof edge …
TOM: … is not depositing right at the foundation perimeter. All of those things together will help you reduce the volume of moisture that’s getting in the crawlspace and then the amount of that that can evaporate up into the house.
LESLIE: And you know, Greg, one more thing that you can do, now that you’ve managed everything outside and really controlled that moisture, you want to install a bathroom vent fan into that bath as well. This way, whatever moisture you’re generating inside the bathroom can be brought outside.
You want to make sure it’s properly vented to the outdoors and if you can, have an occupancy sensor installed; it’ll just make it simple to use. It’ll come on when you’re in there and go off when you’re out. This way, you don’t have to worry about a family member who might forget to put it on; not to name any names.
GREG: OK. That makes sense. I thank you much.
TOM: You’re very welcome. Thanks so much for calling us at 888-MONEY-PIT.