What Causes Moisture in Basement Walls? By Water Damage Advisor Posted on December 3, 2016November 14, 2021 The basement is often the most common site of water damage in the home. Basements are particularly at risk thanks to moisture attacking from multiple directions, coming both from within the home and through the external soil. Moisture present in basement walls and floors can cause the growth of mold and mildew, which can pose serious health risks, such as respiratory illnesses, headaches, coughing, wheezing, and other hay-fever-like symptoms. Even if you don’t spend a significant amount of time in your basement, air often cycles through your basement to other rooms of your home through ducts and ventilation. Therefore it’s important to understand the causes of moisture in basement walls. Sources of Moisture in Basement Walls There are three main sources of moisture in basement walls: External liquid water, either from groundwater or rain: A one-inch rainstorm causes 1,250 gallons of water to fall on the roof of a 2,000 square foot home. Without proper rain gutters or drainage, this water can seep through a home’s foundation. Interior humidity: Regular household activity often causes the release of moisture into the air, including showering, cooking, the use of humidifiers, and washing and drying clothes. Interior moisture is especially common in finished basements where frequent showering or cooking takes place. Of course, leaky or broken pipes and flooding are another interior cause of moisture. Exterior humidity: Warm air that enters through basement windows or pores in concrete can condense on the cool concrete walls and cause condensation. The three main sources aside, there are also several other common causes of moisture buildup, many of which are preventable if proper care is taken at the time of home construction. One common cause is a failure to slope the ground around the house away from the home’s foundation. If the land is kept level or slopes toward the house, this can direct water directly into the basement. For the same reason, every home’s roof needs an effective gutter system. Without a gutter with a downspout that offshoots water at least four feet from the home’s foundation, water will simply pool around the edges of the house. A proper underground drainage system also goes a long way to avoid the problem. Another typical cause of moisture entering the home is a cracked foundation. When floor joists aren’t properly anchored to the foundation, or soil starts to settle around the home, cracks can form in the home’s foundation. Moisture enters through these cracks and can cause serious damage. Preventing Moisture in Basement Walls If you’re seeing significant humidity in your basement, you may need to take the following measures: Control interior moisture. Install proper ventilation in humid areas like bathrooms and kitchens, and stop using humidifiers. Seal any air leaks. Common air leaks include clothing dryer vents, air conditioners, and heating systems. Don’t ventilate your basement with outside air. Opening windows can cause condensation to form on walls, especially when it’s hot outside. Ensure proper grading around the home, and install a proper gutter. Install a proper drainage system in the ground around your home. If you have any common signs of moisture in your basement, including water leaks, high humidity, or water stains on basement walls, contact a water restoration specialist immediately.