Handyman

How to deal with basement dampness

Drop in and see what problems water condensation can create...
Drop in and see what problems water condensation can create... File photo

Last year, we bought a house in the suburbs, and we’ve decided that we’ll need to refinish part of the basement. The basement is very humid in the summer, and the dehumidifier we have isn’t up to the job. The excessive moisture is creating mold problems, attracting bugs, and causing water stains on walls.

We don’t want to spend a lot of money to fix this problem. It is not water intrusion during heavy rains, but dampness. We have been told by some people we have brought in that we need a new heating/cooling system. Others suggest really expensive work to create drainage along the walls to reduce the humidity, and thus the water stains. Is there another option?

The folks offering these suggestions, while they are looking for work, also have seen the situation first-hand, and I have not.

The basement is the lowest point of a house, and you have to expect moisture intrusion. The trick is finding ways to manage the moisture so it doesn’t run wild and do damage.

Along all four sides of my basement, perimeter drains have been cut so that any moisture from the outdoors behind the walls, and any droplets appearing on the interior of the walls, is carried to a central French drain that leads to a sump. That system is designed to manage rain as well as a rising water table. It does not cut humidity levels.

That is handled by a properly sized dehumidifier that drains automatically into the sump and keeps the basement at a recommended 40 percent relative humidity during the summer. As the humidity is removed from the air, more moisture is drawn in to replace it, so on very humid days, the dehumidifier works nonstop, even on its energy-saving function.

I’d ask the contractors how French drains are supposed to help in removing moisture from the air. I have them, and I still need a dehumidifier big enough to handle the space. I’d also look a little further into the heating/air system situation.

If you buy an older house and the basement hasn’t been touched — especially given that basements are the typical way people expand their living space — you might find there was a good reason.

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