How to Reduce Basement Humidity

CaponeMax asks,

I live in northern Maine, and my basement is starting to get a weird odor. It's not getting wet and there are no water issues. A friend says I need to get a dehumidifier. The basement has our laundry area and my “man cave.” I was wondering what kind of dehumidifier I should buy. I've seen some that have heat and AC. Will this type of dehumidifier help the rest of the house, or just the basement? Please recommend a brand and/or model.

Our Answer

A humid man cave sounds pretty unpleasant, so let’s get that back into shape for you.

First of all, you’re getting high humidity because of excessive moisture outside the basement. The fact that you’re not getting water doesn’t mean the problem doesn’t exist. Moisture that collects around the foundation perimeter emanates into the basement because the foundation is very porous. The solutions to basement humidity don’t begin with a dehumidifier. To address the root problem, you’ll need to take steps to redirect water away from your home’s foundation.

That starts with your gutters. Make sure your gutter system is properly sized for your house so you don’t get a gutter that becomes overwhelmed. Keep the gutter system in good repair, and keep your gutters clean and free-flowing. As for downspouts, you want one for every 400 to 600 square feet of roof surface. And you want to make sure the downspouts are extended 4 to 6 feet away from the foundation.

Next, you need to address the grading of the soil around your home’s foundation. You want the slope to drop away 6 inches over 4 feet. The type of soil that you add is also very important. Don’t use topsoil — use clean fill dirt. Topsoil is very organic and will hold water. Fill dirt, on the other hand, can be tamped down and packed in to get a solid slope that water will run over. After you have the proper grade established, then you can add a little topsoil over the fill dirt to plant some grass seed or put some mulch or stone or whatever you want.

As a last step, after you’ve done everything you can to keep water away from the foundation, you can add a dehumidifier in the basement. Find one that has a condensate pump either built in, or as an accessory. Otherwise you’ll spend a lot of time emptying the pan.