How to Get Rid of That Musty Basement Smell, According to Experts

While a musty smell in the basement might seem normal, it can often be a sign of a more serious problem, like hidden moisture or mold. Before it turns into a bigger issue, it’s important to identify the source of the smell, deal with the root of the problem, and freshen things up. After all, doesn't every inch of your home deserve to smell as fresh can be? (Moreover, don't you deserve to exist in such a space?)

Our experts offer insight into what might be causing that musty smell, as well as how to deal with each issue and when it might be time to call in a professional.

Why Basements Can Smell Musty

Basements can develop their trademark musty odors for a variety of reasons. For one, accumulated dust, dirt, and clutter can trap odors. “Deep cleaning and decluttering, especially removing or washing fabrics and upholstery, help reduce smell sources,” says Isabella Flores, cleaning expert with Sparkly Maid San Diego. “Activated charcoal or baking soda placed around can absorb lingering odors.”

A few additional areas to investigate if you need help pinpointing the source of a musty smell in your basement might include old carpet, boxed clothes, unused upholstery, and even dirty air or furnace filters. “To fight these, clean and thoroughly dry affected materials, replace or repair water-damaged items, maintain and clean HVAC systems regularly, and inspect for and try to fix hidden leaks as soon as possible to prevent moisture buildup,” advises Alicia Sokolowski, co-CEO of AspenClean

From there, if odors still persist, explore the following common causes below, along with their fixes.

When Moisture Is the Culprit

Moisture creates a damp environment, ideal for bacteria and fungi to grow. “When these microorganisms break down organic materials, they release microbial volatile organic compounds, or MVOCs, that produce a musty or earthy smell,” explains Sokolowski. “Even hidden moisture behind walls or under carpets can lead to this odor over time.”

There are several crucial steps to combat moisture issues, according to Michael Rubino, council-certified mold remediator and founder of HomeCleanse.

• Use a dehumidifier: These machines will eliminate moisture from the air. 
• Invest in a smart thermostat: Be sure to choose one that monitors humidity in real time so that you can quickly resolve issues as they pop up.
• Clean up spills and pooled water: Standing water raises humidity levels and encourages mold growth. Dry spills, leaks, and condensation as soon as possible.
• Fix leaks promptly: Even small leaks add moisture to the air. Regularly inspect pipes, water heaters, and basement walls for leaks—and repair them immediately.
• Ensure doors and windows are properly sealed: Sealing gaps prevents outdoor humidity and rainwater from seeping inside, helping maintain stable indoor moisture levels.
• Keep windows and doors closed during rainy weather: Rain and high outdoor humidity can increase indoor moisture levels. Keep basement windows and doors closed to prevent excess dampness.
• Maintain and clean gutters: Clogged or damaged gutters can cause water to seep into the foundation, leading to moisture intrusion and higher humidity. Regularly clean and maintain gutters to direct water away from the house.
• Ensure proper insulation: Poor insulation helps regulate temperature and reduces moisture buildup.
• Increase air circulation: Use fans, open doors, and keep vents clear to improve airflow and prevent humidity from becoming trapped.
• Reduce carpeting: Carpets retain moisture, making them prone to mold growth. Opt for hard flooring like tile, vinyl, or sealed concrete instead.
• Store items in waterproof containers: Cardboard boxes and fabric absorb moisture, leading to mold. Store items in airtight plastic bins to prevent dampness and contamination.

When Mildew Is the Problem

Mildew is just mold that hasn’t gone full-blown yet, says Matt Gorbacz, owner and president of Clean Air Technologies. “It grows fast on anything organic when the air stays moist,” he warns. “It’s like the warning sign before a real mold problem. Bleach water or a proper mold cleaner on hard surfaces works fine, but if it keeps coming back, you’ve still got a humidity issue. Fix that, or it’s a losing battle.”

Additionally, there are several crucial steps to combat mildew issues, according to Rubino:

• Switch cleaning products: You want products that eliminate particles from surfaces and don’t negatively impact your indoor air quality. These include botanical products with surfactants, microfiber material, a HEPA vacuum, and a botanical laundry additive for all of the machine-washable items. 
• Clean the entire indoor space frequently: This eliminates microscopic particles like mold spores and bacteria so that levels remain low in the home, reducing the chances of growth developing. Focus particularly on dusting because microscopic particles like mold spores settle where our dust settles. 
• Reduce clutter: Make surfaces easier to clean thoroughly, reducing the number of mold spores and other contaminants in the home.
• Wash porous materials: Clean items like bath mats, towels, bedding, shower liners, blankets, curtains, and anything else machine-washable with a botanical laundry additive like EC3.
• Schedule an HVAC professional: Have your unit serviced biannually to ensure there is no contamination in the system and that it is running properly.
• Invest in air purification: You want the technology that removes the smallest particles possible. The fewer small particles inside, the healthier the indoor air quality and the less likely microbial growth will develop.
• Upgrade your filters: Choose the highest-rated MERV filters that the HVAC system can handle and change them on time. This will help eliminate small particles like mold spores so that they don’t continue to build up inside. 
• Stay on top of houseplant maintenance: These are prone to mold growth, so avoid overwatering, clear debris, etc.

When Poor Airflow Is the Issue

Poor airflow causes musty odors, Sokolowski says, as the lack of airflow allows moisture and stale air to become trapped and creates an environment where mold, mildew, and bacteria thrive. “Without proper circulation, these microorganisms release gases that produce the distinct musty smell,” she says. “Over time, areas with stagnant air—like closets or basements—develop a persistent, unpleasant odor.”

The best way to combat this is to increase ventilation. Open windows when the weather is dry, enlist the help of oscillating fans, and keep interior doors open to other rooms in the home. “Make sure to clear your air vents and filters regularly to ensure the fresh air circulates through the space,” Sokolowski says.

When to Call a Professional

Keep in mind that visible mold may just be the tip of the iceberg—there could be more hidden behind walls, under flooring, or in other unseen areas. “Because of its ability to stay hidden, it's important to test for mold to uncover both its location and the source of the moisture causing it,” Robert Weitz, principal and founder at RTK Environmental Group, explains. “DIY kits are usually unreliable, so it's best to call in trained mold inspection professionals, who can accurately assess the situation and map out a solution.”

Even if you don’t see visible signs of mold, it could be hiding in places like the back of drywall, behind paneling, under carpets or padding, on cardboard storage boxes, or around pipes. “The only way to know what you are dealing with is to test, and an independent test will pinpoint where the issue is and recommend a blueprint for remediation,” Weitz says. “It could be a leak in the foundation, poor drainage, high humidity, or a leaky pipe causing mold. Very often the mold and the source could be hidden and only detectable by the professional with moisture meters, thermal image, etc. If you suspect mold, it’s time to act.” 

Because, as it turns out, a musty basement smell isn't just unpleasant—it could be harmful.