NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665

May 20, 1999

A Dry Basement Keeps the Whole House Healthy

Keeping water out of your basement may help prevent a host of health problems for you and your family, says a North Dakota State University engineer.

"Mold spores are everywhere and mold will grow on any organic material. Unfortunately, your whole home is a target," says Ken Hellevang, an agricultural engineer with the NDSU Extension Service. "Humidity levels above about 70 percent create an ideal environment for molds." Mold can produce a range of health effects in humans ranging from a runny nose and watery eyes to chronic breathing problems and severe allergic reactions.

Recent rains across the region have prompted a flurry of calls about watery basements for Hellevang. Topics have ranged from cleaning up after water has flooded a basement to preventing seepage and condensation problems.

Looking outside may be the first step to solving basement water problems, Hellevang says. Make sure gutters and downspouts are clean and in good repair. Downspout extensions should carry water several feet away from the house. "The worst thing you can do is dump all the water from your roof right next to your foundation," he says. A one-inch rain on a 1,000 square foot roof is more than 600 gallons of water.

The ground around the house should slope away from the foundation at a rate of at least an inch per foot of distance away from the house. Fill depressions near the foundation where where the ground has settled or soil has been moved. Use a low permeable soil such as clay to encourage the water to drain away from the house.

Window wells are another problem area. They should be well sealed to the house and extend out of the ground to keep water out. The ground around them should be graded to promote drainage, Hellevang says. The window well should have a deep gravel base or a link to the home's foundation drain tile to remove any water that does get into it.

If correcting exterior problems doesn't solve interior basement water problems, options become much more costly and difficult, Hellevang says. Localized problems might be solved by removing part of the basement floor and installing a sump pit and sump pump. More extensive problems may require additional excavation in the basement or outside the foundation to install drainage tile.

"It's very difficult to solve these problems after a house is built," Hellevang says. "That's why it's so important to address drainage while the house is being built. New homes should have drain tile installed inside and outside the basement." The tiles should be surrounded with gravel to help promote drainage and protected by a fabric barrier to keep out dirt. Basement floors should be poured on four to six inches of gravel to help promote drainage and basement walls should be backfilled with gravel for the same reason.

Moisture from heavy clay soils in contact with concrete basement floors can make its way through the concrete and escape into the home as water vapor. Several gallons of water per day can enter the home through basement walls and the floor.

"You want to create a drainage envelope around your house," Hellevang says. "Our heavy clay soils will hold water against the floor and walls. Heavy clay soils can also expand, causing damage to basement walls."

For basements that are plagued with high humidity and condensation, dehumidifiers and air conditioners may be the best answer. "Once the outside temperature gets warmer than the basement temperature, ventilation isn't going to help humidity levels much," Hellevang says. "In fact, it may make things worse." That's because the water-holding capacity of air is reduced as the air is cooled. For example, air that has 40 percent relative humidity at 80 degrees increases to 80 percent relative humidity as that air is cooled to 60 degrees.

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Source: Ken Hellevang (701) 231-7243

Editor: Tom Jirik (701) 231-9629