Why Does My Basement Smell After It Rains?

Updated February 21, 2017

If your basement smells after it rains, you may have a mould problem on your hands. The cool, moist atmosphere in basements provides the perfect growing conditions for bacteria. A smelly basement is not only unpleasant; it can also cause health problems in residents. Mold can lead to structural damage down the road. If you notice a foul, musty odour coming from your basement after rain, take the necessary steps to eliminate mould and prevent it from returning.


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 mould smell to become more pungent and noticeable. Storing plants and other organic matter in your basement can also cause mould to grow. Homes in humid climates are more susceptible to mould than homes in dry climates.


The presence of mould has a negative effect on the air quality of a home. Even mould 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.


Getting rid of the smell in your basement after it rains means getting rid of mould. 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 mould is visible, and clean surfaces by scrubbing them down with the detergent/water solution. After you've cleaned down the mouldy 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.


Install a dehumidifier to keep mould out of your basement. This keeps the air dry, preventing mould 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 mouldy smell after rain. Also avoid putting wall-to-wall carpeting in the basement.

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About the Author

Charlie Higgins is journalist, editor and translator based in Buenos Aires, Argentina. He has written for a variety of lifestyle and niche market websites, including International Food Trader, The Olive Oil Times, microDINERO, Sounds and Colours, Connecting Worlds and The Buenos Aires Reader.