House Grail is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. Learn more.
What Is a Good Humidity Level for a Basement? Tips, Signs & Risks
The humidity level in your basement plays a crucial role in determining your family’s health. It also ensures the safety of your possessions and your home’s structural integrity.
Basement humidity levels should be relative to the rest of the house. Usually, basements are colder than other rooms in the house, and they also have lower air circulation. The lack of air circulation often causes higher humidity levels.
Maintaining a good basement humidity level is crucial as it prevents mold growth and other damage to your home. But what is the ideal basement humidity level? It is recommended to have a humidity level between 30%–50%. Keep reading as we explain further and answer any other questions you may have. So, read along with us!
Ideal Humidity Level for a Basement
The ideal basement humidity level (finished or unfinished) is between 30%–50%. While it may seem like a high amount, it’s perfect and will keep your home safe and comfortable. Any humidity level above 60% is considered high and any level below 25% is low.
If the humidity level is too high, mold can grow on walls or floors in your home. This humidity level may change depending on the weather. Let’s look at basement humidity levels in different types of weather.
Different types of weather:
Basement Humidity Levels During Summer: The higher the temperature outside, the more likely it will be for your basement to get hotter than usual. Due to this reason, there’s an increase in moisture in the air, which leads to higher humidity levels inside your house. The ideal basement humidity level during summer is 50%. The warm air outside rises and pushes down cool air into the basement.
Basement Humidity Levels During Winter: Winter is the season when you must pay extra attention to your basement. It’s prone to humidity, especially if you live in a cold place with snow and ice. As a result, even slight amounts of moisture can cause mold and mildew growth. This can be dangerous for your health. The basement humidity level in winter should be around 25%–40%.
Why Are Basements Likely to Have High Levels of Humidity?
There are several reasons your basement has high humidity levels.
Here are some of them:
They Have Few Windows: Basements are dark, damp, and enclosed spaces. They’re also airtight, meaning any water vapor in the air has a hard time escaping. It can cause an increase in humidity and moisture levels.
They’re Underground:The ground absorbs water like a sponge. So, when it rains heavily, all that water will seep into your basement through the foundation walls or floors. The moisture from rainwater also enters your home through cracks in concrete slabs.
They’re Made of Concrete: Basements are humid because they’re often surrounded by concrete or other materials that don’t allow air to move through them. It means that the air inside the basement can become warm and humid over time, leading to mold growth and other problems related to water damage. That’s why homeowners must take steps toward prevention, such as installing dehumidifiers in their basements.
Tell-Tale Signs That Your Basement Has Excess Moisture
Excess moisture in the basement can be an expensive problem. If you notice any of the following signs in your home’s basement, it could be a sign that there’s excess moisture.
Water Stains: If you see water stains on your basement walls, it indicates excess moisture in the walls. It needs to be treated immediately. These stains show that water is seeping through the drywall and into the studs of your house. If left untreated, it’ll lead to mold growth in the wall area and eventually cause damage to your home.
Mold and Mildew: The most obvious sign of excess moisture is mold and mildew. If you have a musty odor or a black growth on your walls, ceiling, or floor, you likely have mold in your basement.
Excess Condensation in Windows: Condensation forms on the inside part of windows when there’s too much moisture in the air. It is a sure sign that your basement is too damp.
Concrete Spalling: Concrete spalling occurs when water gets into cracks in the concrete, causing it to break apart, flake, and peel off. The water will eat away at the concrete and weaken it.
Odors: If there is an odor in your basement, it could be because of excess moisture. The smell can also come from the air in your basement or mold forming on the walls and floor. If you notice this odor, it’s time to act fast and tackle the problem before it gets out of hand.
Rotting: If you see rotting wood or drywall in your basement, this indicates excess moisture. When wood rots, it begins to decay on the surface of the wood as water seeps into it. Also, water destroys its natural structure and mold grows on top of it.
Risks Associated with High Humidity Level in Your Basement
Health Issues: Health problems can be caused by mold or mildew on surfaces, such as walls and floors. When these microorganisms begin to grow, they release spores that cause allergies, asthma attacks, and other respiratory problems. Besides, these spores can lead to severe health problems, like lung infections.
Damage to Walls and Wood: Basement walls may become moist or wet if there’s excess moisture in the air. The wood framing on concrete block foundations will rot faster when exposed to high humidity levels for extended periods.
Mold: If you see mold growth on any surface in your basement, there’s moisture accumulation. Address it immediately before it causes any further damage to your basement.
Ways of Reducing Basement Humidity Level
There are several ways of reducing it in your basement.
Here are some of them:
Keep the Basement Clean: Keeping your basement clean reduces its humidity level. It means cleaning any wet flooring with a mop or broom often. Also, ensure debris doesn’t accumulate on the flooring. It’ll cause mold growth underneath it. Remember that moisture can also accumulate under clutter. So, ensure you keep everything tidy and clean.
Turn Off Humidifiers: If you have a humidifier in your basement, turn it off. When a humidifier is running, it adds moisture to the air, meaning that there will be more moisture in your basement.
Use Fans: Fans help ventilate moist air out of your basement. This way, warm air can circulate through it. They also help remove moisture from the air. The moisture evaporates into the atmosphere before it settles back onto your possessions.
Invest in a Dehumidifier: Dehumidifiers are the most popular way of reducing humidity levels in a basement. They remove moisture from the air and dry your basement. The best dehumidifiers for basements come with various humidity settings. This way, you can adjust them depending on how much moisture is in the air at any given time.
Seal Any Gaps: Sealing gaps prevents excess moisture from entering your basement and reduces humidity. You can apply caulk or a spray foam sealant after cleaning any debris that may have built up over time.
Turn Up the Heat: Your home’s heating system is one of the best ways to lower humidity in a basement. The heat from your furnace will cause moisture in the air to evaporate, leaving behind dry air. It’s helpful during the cold winter months when basement temperatures are low.
Ensure Your Gutters Are Clean: Leaky gutters can cause water to drip into your basement during rainy seasons, causing moisture buildup inside the soil. It’ll seep into the foundation, causing it to rot over time. It also leads to mold growth and other forms of decay.
Use a Plastic Barrier to Cover Dirt Basement Floors: Usually, dirt floors are damp as they accumulate moisture from the outside air. The moisture collected in the dirt floor increases basement humidity levels. So, it’s crucial to cover your dirt floor with plastic. That way, it’ll not absorb too much moisture from the surrounding atmosphere.
Coat the Walls Using a Waterproof Material: If you have a basement with concrete walls, coat them with waterproof material. It’ll ensure that water doesn’t seep into the walls, thus reducing the humidity levels.
In a nutshell, a good humidity level for a basement is 50%. If it’s higher, you risk mold growing on walls and surfaces. On the flip side, materials in your basement can experience damage due to moisture entry if it’s lower. You’ll start seeing bubbling, peeling, cracking, or warping.
Either way, if the humidity levels are too high or too low in your basement, it’ll cost you to maintain proper levels. We hope these tips have helped you, particularly if you have clammy basements. Follow these steps, and you’ll enjoy being in your home’s basement again.
Pete has been working in the trades since high school, where he first developed a passion for woodworking. Over the years, he has developed a keen interest in a wide variety of DIY projects around the home. Fascinated by all sort of tools, Pete loves reading and writing about all the latest gadgets and accessories that hit the market. His other interests include astronomy, hiking, and fishing.
As the founder of House Grail, Pete's primary goal is to help consumers make educated decisions about DIY projects at home, in the garage, and in the garden.