Missouri/Illinois St. Louis Regional
Homeowners :: Moisture in Basements and Crawlspaces
Moisture in basements or crawlspaces could be caused by water leaks or high humidity. Both can lead to mold, mildew, or other biological growth. Depending on the severity, conditions can lead to rot, structural damage, premature paint failure, and a variety of health problems.
Water Leaks
If the problem is localized (a spot on the ceiling, wall, or corner) it is possibly caused by a water leak. Water can seep into your house from the outside through a leak in the foundation, or small gaps around windows or doors. Water can also come from inside your house from a leaking water pipe, toilet, shower or bathtub.
If you have standing water on the floor of your basement after a heavy rain then it is likely from a leak in the foundation. You will need to:
- Clean rain gutter and redirect downspout runoff away from the foundation.
- Make sure the ground around the house slopes down away from the foundation. If necessary, re-grade so the ground does slopes away.
- If you have a sump pump, make sure it is working properly.
Reducing indoor humidity
High indoor humidity caused by normal activities of everyday living, such as showering, cooking, and drying clothes, could also be a source of your problem. A damp basement is commonly caused by moisture migrating through a concrete foundation. There may not be a sign of any leak or standing water, but the moisture evaporates, increasing indoor humidity. Another common cause is condensation on the cold concrete walls and floors during humid months.
- If your basement has a dirt floor, cover the floor completely with plastic to slow down water vapor coming through the soil.
- Ask a contractor to check your home for adequate ventilation.
- Air sealing and sealing duct work can help to prevent high humidity levels in your home.
- During hot humid months, using a dehumidifier in the basement can reduce condensation on the walls. This may work better after you've sealed air and duct leaks to reduce the amount of humid outdoor air you are bringing into the basement.
