University of Minnesota Extension

FO-07051     Revised 2006  

Moisture in Basements: Causes and Solutions


Basement Moisture Sources

Rainwater/ground water diagram

Rainwater and Groundwater

In a one-inch rain, 1,250 gallons of water fall on the roof of a 2,000-square-foot house. Without proper grading, gutters, and downspouts, some of this water flows into the basement. The below-grade water table can also rise due to flooding or seasonal site conditions. This is why drain tile systems are recommended around basement walls even in sandy or gravel soils.

Interior moisture sources diagram

Interior Moisture Sources

Moisture is generated inside of basements from people and their activities. Common sources are humidifiers, unvented clothes dryers, showering, and cooking. When basements are finished, these activities increase. Another source that can be thought of as internal is the moisture contained in new concrete after construction. In a typical house, this can amount to 0.2 gallons per square foot of wall, and 0.1 gallons per square foot of floor. It may take many months or even years for a new house to come into equilibrium with its environment.

Ventilation with Humid Outside Air

In the summertime, basement windows may be opened for fresh air. If the outside air is warm and humid, it will condense on the cool basement wall and floor surfaces. Many homeowners see this moisture and believe they are experiencing basement wall leakage, when in fact the accumulated moisture is from condensation.

 Condensation diagram
HOME NEXT: Moisture Movement Mechanisms

-

The information given in this publication is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by University of Minnesota Extension is implied.

Produced by Communication and Educational Technology Services, University of Minnesota Extension.

In accordance with the Americans with Disabilities Act, this material is available in alternative formats upon request. Please contact your University of Minnesota Extension office or the Extension Store at (800) 876-8636.


▲ Back to top

Agriculture

Agricultural Business Management

Crops

Livestock

Community

Community Economics

Leadership & Civic Engagement

Signature Initiatives

Environment

Forestry

Environmental Science Education

Water Resources

Housing

Family

Family Relations

Family Resource Management

Housing

Signature Efforts

Garden

Horticulture

Commercial growers

Food

Youth

Extension