How to Reduce Crawlspace Moisture
LESLIE: Alan’s up next on the line and he’s looking to get rid of some moisture from his basement.
Alan, welcome to The Money Pit.
ALAN: Thank you for taking my call.
LESLIE: You’re so welcome. Tell us what’s going on.
ALAN: We recently had a home inspector tell us that due to the moisture content in our crawlspace that we should put a powered ventilation system under there. I live in a small town and there’s no one locally that seems to have anything and I was wondering if y’all had any suggestions.
TOM: Sure. If it’s a crawlspace, there’s a couple of things you want to do, Alan. It’s not just a matter of putting the fan in. There are a number of things you can do to reduce moisture. The first thing you need to do is to improve your grading around the foundation perimeter so that the soil slopes away from the walls. This is going to help prevent water from collecting at that foundation where it can leak into the house and raise the moisture level in the crawlspace. The second thing is your gutter system. Make sure that it’s clean and free-flowing. Those two things are the biggest contributors to crawlspace moisture.
Next, you need to get into the crawlspace and you want to install a vapor barrier across the floor of the crawlspace. That is usually done with plastic sheeting. You want to lay it end to end. You want to have as few seams as possible. It’s really hard to work down there with those big sheets of plastic but do the best you can to get as much of that soil covered as you can.
And then lastly, you can install a fan. Now the kind of fan that you would install is a foundation fan that fits in the side of one of those crawlspace vents. It’s usually the same size of a block, which is 8 inches by 16 inches, but there’s one, critical difference with the way the fan works: it’s wired to a humidistat, not a thermostat like an attic fan would, so that whenever it gets really damp there, then the fan kicks on and pulls air across that crawlspace surface and dries it out. Where do you find that? An electrical supply store should have absolutely no problem ordering one of those fans for you along with the humidistat that’s needed to operate it.
ALAN: Very good. Well, I’ve already done the plastic thing so I’m glad to hear that there are some available with humidistats so that they won’t run all the time.
TOM: Nope, that’s definitely the way to go. And do check an electrical supply store. You shouldn’t have any problem finding one. OK?
ALAN: Thank you so much.
TOM: You’re welcome. Thanks so much for calling us at 1-888-MONEY-PIT.