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Basement Smells Musty? 5 Steps That Actually Clear the Odor

A musty basement smell means damp air and mildew somewhere. Find the moisture, clean the mildew, then keep the air dry so the smell stays gone.

By Jamilur Rahman Updated November 5, 2026 · 6 min read

Time
1 hour, plus a few days to air out
Cost
Under $20
Difficulty
Medium
A concrete basement corner with cardboard boxes on the floor and damp-looking walls
In this guide
  1. Quick answer
  2. Free vs. permanent fix
  3. What you'll need
  4. Why it happens
  5. Try this first (free)
  6. When free fixes aren't enough
  7. Buy the fix
  8. Basement smells like mildew: clean it, do not just cover it
  9. Cheap fixes outside the house that dry the inside
  10. What to skip
  11. FAQ
  12. Related problems

Quick answer

A basement smells musty because damp air lets mildew and mold grow on walls, boxes, fabric and floors. To clear a basement that smells musty, find the source of moisture, clean off any mildew with soap and water, and air the space out. In small, closed-off spots, moisture absorber buckets keep pulling humidity out so the smell does not return.

Free fix vs. permanent fix

Free fix · 1 hour

Find the damp, clean it, air it out

  • Look for leaks, wet spots and damp stored items
  • Scrub small mildew patches with detergent and water
  • Throw out anything soaked, like old cardboard or carpet scraps
  • Run fans and open windows, but only on dry days

How long it lasts: A few weeks if the basement stays damp. It can last much longer if the moisture source is fixed.

Most readers choose Permanent fix
Moisture absorber buckets (illustration)
Illustration

Moisture absorber buckets in closed corners

Airing helps on dry days, but damp air comes back as soon as you stop. Absorber buckets keep drawing moisture out of the air in a small, closed area like a storage corner or basement closet. They help the smell stay gone once the source is fixed.

What to get: Moisture absorber buckets

How long it lasts: A month or two per refill, depending on how damp the space is. Replace them as the label says.

Check price on Amazon

As an Amazon Associate I earn from qualifying purchases.

What you'll need

  • Scrub brush and dish soap

    For small patches of mildew on hard surfaces

    You have it

  • Box fan

    Keeps the air moving while it dries

    You have it

  • Plastic storage bins

    To get boxes off the floor

    You have it
  • Digital hygrometer (illustration)
    Illustration

    Digital hygrometer

    Shows the real humidity, so you know when it is working

    Check price
  • Our pick
    Moisture absorber buckets (illustration)
    Illustration

    Moisture absorber buckets

    For closets, storage corners and other small closed areas

    Check price
  • Dehumidifier (illustration)
    Illustration

    Dehumidifier

    For a whole basement that stays damp

    Check price

Why it happens

1

High humidity

Basement walls and floors are cool, so damp air condenses on them in warm months. Humidity above about 60 percent is when mildew grows.

2

Water coming in

Small leaks through foundation cracks, around windows or from a pipe wet the walls and floor. Rain that runs toward the house instead of away from it makes it worse.

3

Damp stored items

Cardboard boxes, old carpet, fabric and paper soak up moisture and grow mildew. They also hold the smell after the damp is gone.

4

Poor airflow

A closed basement with no ventilation traps damp air. Laundry that dries down there, or a dryer vent that leaks, adds more moisture.

Try this first (free)

Do these in order, starting with the simplest.

  1. Find where the smell is strongest

    Walk the basement and sniff along walls, corners, closets and boxes. Look for dark spots, peeling paint, white crusty marks on concrete or damp patches. Touch the walls and floor to feel for moisture.

  2. Check the humidity

    Tool used: Digital hygrometer

    Put a hygrometer in the middle of the room. Aim for 30 to 50 percent. If it reads above 60 percent, the air is damp enough to grow mildew.

    Digital hygrometer (illustration)
    Illustration

    Tool for this step

    Digital hygrometer · Shows the real humidity, so you know when it is working

    Check price on Amazon

  3. Clean and clear out the damp stuff

    Tool used: Scrub brush and dish soap

    Scrub small patches of mildew, up to about 10 square feet, with detergent and water, and dry the area right away. Throw away soaked cardboard, rugs and anything mildewed that you cannot wash. Move the rest into plastic bins off the floor.

  4. Air it out on a dry day

    Tool used: Box fan

    Open windows and run a fan on a dry, low-humidity day. Do not ventilate on a humid summer day, because warm wet air from outside can make the basement damper.

  5. Set out absorber buckets

    Tool used: Moisture absorber buckets

    Put moisture absorber buckets in closed corners, storage areas and closets, on a tray in case of spills. Check them after a few weeks and replace them as the label says.

    Moisture absorber buckets (illustration)
    Illustration

    Tool for this step

    Moisture absorber buckets · For closets, storage corners and other small closed areas

    Check price on Amazon

When free fixes aren't enough

If the hygrometer stays above 60 percent after a week of airing, or the smell is back within days, damp air is still getting in and absorber buckets alone will not keep up in a big open basement. A dehumidifier sized for the room is the stronger tool for that. If you see water on the floor, spreading mold larger than about 10 square feet, or mold after a flood or sewage backup, stop and call a pro. Also call if there is a rotten egg or sewage smell, which can be a gas or drain problem, not mildew.

Buy the fix

Still stuck after the free fixes? These are the products we would look at.

Our picks compared
PickProductFixesWho it's forBuy
Best pick
Moisture absorber buckets (illustration)
Illustration
Moisture absorber buckets
damp air in small closed areas, which keeps the musty smell coming back People with a damp storage corner, a basement closet or a small finished room. Check price
Upgrade pick
Dehumidifier sized for the basement (illustration)
Illustration
Dehumidifier sized for the basement
damp air in the whole basement A basement that stays above 60 percent humidity for days. Check price
Best pick
Moisture absorber buckets (illustration)
Illustration

Moisture absorber buckets

Fixes: damp air in small closed areas, which keeps the musty smell coming back

Look for: A coverage size on the label that matches your space; A spill-resistant tub or catch tray; Refills or replacements that are easy to find.

Who it's for
People with a damp storage corner, a basement closet or a small finished room.
Honest downside
Your whole basement is damp, or you have kids or pets that could tip the tub. Use a dehumidifier and keep the liquid out of reach.
Check price on Amazon
Upgrade pick
Dehumidifier sized for the basement (illustration)
Illustration

Dehumidifier sized for the basement

Fixes: damp air in the whole basement

Look for: A pint rating that fits your square footage; A continuous drain hose option, so you do not empty a tank; A built-in humidity setting.

Who it's for
A basement that stays above 60 percent humidity for days.
Honest downside
You only have a small closet to dry. Absorber buckets are enough there.
Check price on Amazon

As an Amazon Associate I earn from qualifying purchases. We don't show prices because they change, so use the button to see today's price.

How we picked: How we picked: this page is based on EPA and extension guidance on indoor humidity and mold, product instructions from moisture absorber and dehumidifier makers, and the problems and fixes people report in reviews. We do not test products by hand.

Basement smells like mildew: clean it, do not just cover it

Mildew smell comes from a living growth, so air fresheners only mask it. Scrub hard surfaces with detergent and water, and let them dry fully. Fabric, carpet and cardboard that smell of mildew usually cannot be saved. Wear gloves and a mask while cleaning, and do not mix cleaners.

Cheap fixes outside the house that dry the inside

  • Gutters: keep them clear, so rain does not overflow at the wall.
  • Downspouts: extend them several feet away from the foundation.
  • Soil: slope the ground away from the house, not toward it.
  • Dryer vent: make sure it exhausts outside, not into the basement.

What to skip

Air fresheners, bleach and scented sprays

Sprays cover the odor for a few hours and leave the mildew alone. Bleach is not needed for small mildew patches, and mixing it with other cleaners can release harmful fumes. Detergent, water and drying do the job.

Frequently asked questions

Why does my basement smell musty?
Mildew and mold growing in damp air. The smell comes from gases they give off. The air is usually damp because of high humidity, a small leak or wet stored items.
Why does my basement stink even when it is dry?
Mildew can stay in boxes, carpet and fabric after the damp is gone. A dry floor drain can also let sewer smell up. Pour a quart of water into any floor drain to refill the trap, and remove old stored items that smell.
How do I get rid of mildew smell in the basement?
Find and fix the moisture, scrub mildew off hard surfaces with detergent and water, throw out items you cannot clean, and dry the air. Without the dry-air step the smell comes back.
How do I stop the basement smell from coming back?
Keep humidity under about 50 percent, store things in plastic bins off the floor, keep gutters and downspouts pointed away from the house and use absorber buckets or a dehumidifier.
When is a basement smell dangerous?
A rotten egg smell can mean a gas leak, so leave and call the gas company. A sewage smell, a large patch of mold or any mold after flooding needs a professional.

As an Amazon Associate I earn from qualifying purchases. Affiliate disclosure

Moisture absorber buckets (illustration)
Illustration

Our pick: Moisture absorber buckets

Check price