Basement Humidity: What's Normal?

Wednesday, March 27th, 2019 by Shane McClintic


Basement humidity

Every basement is going to have a humidity level. The question boils down to - what is a safe humidity level to have in your home? Safe humidity levels range from 30% up to 50%. Once you get up to that 50% marker in a basement, there is enough moisture in the air to allow some of the common indoor allergens to start to survive and thrive. The most prevalent would be the dust mite. Dust mites can be found in roughly four out of five homes across the United States[1]. Dust mites ingest moisture out of the air, and one of the most common indoor allergens is fecal matter from dust mites. They can live in carpets, furniture, curtains, mattresses, etc. The Center for Disease Control (CDC) recommends, "Keep humidity levels in your home as low as you can--no higher than 50%-all day long."[2]

Once you start getting over 55%, it creates an environment where mold can grow. Mold has the ability to release spores and feed on standard household materials, such as insulation, drywall, carpet, etc., that have been exposed to moisture. If these spores are ingested, it can cause an array of health concerns for you and your loved ones. According to the CDC, "Mold can cause many health effects. Mold can cause a stuffy nose, sore throat, coughing or wheezing, burning eyes, or skin rash for some people. People with asthma or who are allergic to mold may have severe reactions. Immune-compromised people and people with chronic lung disease may get infections in their lungs from mold. Suppose you walk downstairs in the spring or the summer. In that case, some of the more humid months, and you get that damp feeling or a damp smell or a musty basement smell, the relative humidity is likely beyond what should be if you want to make sure that Mold and indoor allergens are not a problem in your home.

At Thrasher Foundation Repair, we receive a lot of phone calls from customers who do not necessarily have groundwater or water entering the basement. Still, they have damp smells, sticky feeling, musty smells in the basement, and they want to get it checked out. I would recommend that all homeowners have their relative humidity checked, especially during the humid spring and summer months, to ensure that you are producing the air quality you want in your basement and ultimately in your home. Meters are readily available at your local home improvement store and can be used to check your home's humidity. Keep in mind that humidity levels change throughout the day, so you will want to monitor more than once per day.

In the video below, Shane McClintic, one of our basement repair experts with over ten years of waterproofing experience, provides more information and explains what an average, healthy basement humidity level is for most homes and symptoms of basement humidity that exceed this level. Shane also discusses how high basement humidity levels can lead to potential health issues, including mold growth, dust mites and allergies.

[1] https://www.lung.org/clean-air/at-home/indoor-air-pollutants/dust-mites

[2] https://www.cdc.gov/mold/control_mold.htm#:~:text=To%20Prevent%20Mold%20Growth%20in,at%20a%20home%20improvement%20store