Get rid of a musty basement smell
A musty smell in the basement means moisture, and usually mold or mildew growing somewhere. Air fresheners won't fix it. Find where the dampness comes from, bring the humidity down, and clean small moldy spots, and the smell goes with them. A cheap humidity gauge takes the guesswork out of it. Keeping a basement below about 50 percent humidity makes it hard for mold to grow.
Why basements smell musty
Basements are cool and sit against the ground, so they collect moisture from leaks, from water seeping through the walls, and from humid air that condenses on cold surfaces.
Mold and mildew need that moisture to grow. The EPA's advice is simple: the key to controlling mold is controlling moisture.
Where the moisture comes from
Damp air condenses on cool walls.
Poor drainage outside the foundation.
Leaks from pipes, the water heater or the washer.
Cardboard and fabric hold moisture and grow mold.
| What you find | Likely cause | Fix |
|---|---|---|
| Humidity over 60 percent | Damp air | Run a dehumidifier. |
| Damp walls after rain | Water outside the foundation | Gutters, extensions, grading. |
| Wet spot under a pipe | Plumbing drip | Fix the leak. |
| Smell near the floor drain | Dry trap | Pour water in it. |
Dry it out
- Find the moistureWith a flashlight, look for damp spots, water stains, white chalky deposits on the walls, drips from pipes, and condensation. Check under stairs, behind stored boxes and around the water heater and washer.
- Measure the humiditySet a hygrometer out for a day. The EPA recommends keeping indoor humidity below 60 percent, ideally between 30 and 50 percent. Basements are often well above that in summer.
- Run a dehumidifierSet it to about 50 percent and run it with the windows closed. Empty the bucket often, or run its hose to a floor drain or .
- Stop water getting inOutside, clean the gutters, add downspout extensions so water lands several feet from the house, and make sure the soil slopes away from the foundation. Inside, fix any plumbing drips.
- Clean small moldy spotsWearing gloves, goggles and an N-95 mask, scrub mold off hard surfaces with detergent and water, then dry them completely. Throw away moldy cardboard and other soft items that can't be cleaned.
- Clear the clutterMove stored items into plastic bins, raise them off the floor, and keep them a few inches from the walls so air can move. Check the smell and the humidity again after a week or two.
Watch it done
- The musty smell is gone or much weaker
- The hygrometer reads below 60 percent, ideally 30 to 50
- No new damp spots, drips or condensation
If the smell comes back
If the humidity stays high with a dehumidifier running, check that the dryer vents outside, and look for a bigger water source, like a leaking foundation crack or a sump pump that isn't keeping up.
If the smell seems to come from a floor drain, pour a gallon of water into it. A dry trap lets sewer gas into the basement.
What a pro typically charges (a rough estimate; prices vary by area): Professional mold remediation often runs $1,000–$4,000 or more, depending on the area. A good basement dehumidifier typically costs $200–$350.
Find mold remediation near you