Why Does My Basement Smell After It Rains?

If you notice a foul, musty odor coming from your basement after rain, take the necessary steps to eliminate mold and prevent it from returning.

Causes

Mold grows in basements that are poorly ventilated or have leaks that trap water and moisture in the room. During and after a heavy rainstorm, water can leak into the basement, causing the mold smell to become more pungent and noticeable. Storing plants and other organic matter in your basement can also cause mold to grow. Homes in humid climates are more susceptible to mold than homes in dry climates.

Dangers

The presence of mold has a negative effect on the air quality of a home. Even mold that is concentrated in a basement that’s rarely used can be dangerous because bacteria enter the atmosphere of the rest of the home. Mold can cause health problems, such as toxic pneumonitis, chronic fatigue syndrome, kidney failure, organic dust toxic syndrome, rhinoconjunctivitis, occupational asthma, psoriasis and even cancer, according to Mold Survivor. Mold can also cause damage to the structure of the home, as well as personal property and ventilation systems, according to FindLaw.

Solutions

Getting rid of the smell in your basement after it rains means getting rid of mold. Wear protective rubber gloves, eye goggles and an N-95 respirator -- items available at any hardware store -- and head down to the basement with a bucket of hot water and detergent that does not contain ammonia. Locate areas of the basement where mold is visible, and clean surfaces by scrubbing them down with the detergent/water solution. After you’ve cleaned down the moldy surfaces, disinfect them with a mixture of water and chlorine bleach. The University of Minnesota Extension recommends 5 cups of water mixed with 1/2 cup of bleach. Keep windows open, and handle bleach with caution, avoiding contact with skin and eyes. Dry the area thoroughly.

Prevention

Install a dehumidifier to keep mold out of your basement. This keeps the air dry, preventing mold from growing. The University of Nebraska-Lincoln recommends placing the dehumidifier at least 6 inches from the wall, allowing air to flow freely to and from all sides of the unit. Close doors and windows for maximum effectiveness. Hire a professional plumber to check your basement for leaks or other issues that may be causing the moldy smell after rain. Also avoid putting wall-to-wall carpeting in the basement.