Musty Smell in Your House? How to Find the Source and Get Rid of It
A musty smell in your house almost always points to hidden damp. Use our room-by-room sniff test to find the source, then fix it for good.
Did you open the front door this week and catch it? That damp, cellar-like odor that wasn’t there in July. A musty smell in your house tends to show up in autumn, when the windows stay shut, the heating comes on and wet laundry starts drying indoors.
The smell itself is a clue. It almost always means moisture is sitting somewhere long enough for mold or mildew to grow, and those growths give off the stale, earthy odor you’re noticing. So if you spray a fragrance over it, it comes straight back. However, find the damp spot and fix it, and the smell goes for good.
Quick answer: Track down where the smell is strongest, fix the moisture behind it (a leak, condensation, poor ventilation or damp laundry), clean any mold off hard surfaces with detergent and water, then dry the air with ventilation or a dehumidifier. Keep indoor humidity between 30% and 50%.
What causes a musty smell in your house?
Mildew isn’t fussy. Dust, cotton, wood and paper all count as food, and most homes sit at a temperature it’s perfectly happy with. As a result, that leaves water as the one ingredient you can actually take away. The EPA guide to mold and moisture makes the same point: the key to mold control is moisture control. It recommends keeping indoor relative humidity below 60%, and ideally between 30% and 50%.
For instance, cooking, showers, breathing and drying clothes all add water to the air. In summer, open windows carry it away. In colder months, however, it lingers, settles on chilly surfaces and feeds the growth behind a musty smell in your house.
Find the source: a room-by-room sniff test
Walk through the house slowly, opening closets and cupboards as you go. The spot where a musty smell in your house is strongest is usually within a few feet of the cause. Then use this table to narrow it down.
| Where it smells worst | Likely cause | What to do |
|---|---|---|
| Bathroom | Mildew on grout, sealant or the shower curtain; steam with nowhere to go | Run the fan for 20 minutes after showers, wash the curtain, and treat black mold on sealant |
| Laundry area | Damp door seal, soap drawer or wet clothes left in the drum | Clean the seal and drawer, then follow our fix for a smelly washing machine |
| Bedroom or closet | Clothes stored slightly damp; condensation on a cold outside wall behind furniture | Pull furniture a couple of inches from walls, air the closet, add moisture-absorbing tubs |
| Around windows | Water on sills and frames each morning | Wipe sills daily and see our guide to stopping condensation on windows |
| Kitchen | Sink drain, dishwasher filter, fridge drip tray or the trash can | Clean the filter and drip tray, flush the drain with hot water |
| Basement or crawl space | High humidity or water seeping in from outside | Run a dehumidifier; check gutters and downspouts |
| Whole house, worse when the heating or AC runs | A dirty filter, wet drain pan or damp air ducts can spread a musty smell in your house through every vent | Change the filter and get the system checked by an HVAC technician |
| Carpet or rug | An old spill or pet accident that never dried; damp underlay | Lift a corner and check the back; deep clean or replace the underlay |
How to get rid of a musty smell in your house, step by step
- Measure the humidity. A digital hygrometer costs less than a takeout meal and shows whether damp air itself is behind the musty smell in your house. For example, readings above 60% need attention.
- Fix the water first. Repair drips under sinks, clear blocked gutters and deal with condensation. Otherwise, cleaning just resets the clock.
- Clean mold off hard surfaces. Scrub with detergent and water, then dry the area completely. Also, wear gloves, open a window, and don’t mix cleaning products.
- Wash or replace soft items. Because curtains, cushion covers, bath mats and throws soak up the odor, put them through a hot wash and dry them fully. Porous items with visible mold, such as old cardboard boxes or ceiling tiles, may need to be thrown out.
- Dry the air. Open windows for ten minutes on dry days, use extractor fans, and run a dehumidifier in problem rooms. If you dry laundry inside, our tips on drying clothes indoors without the damp will help.
- Soak up what’s left. Once the source is fixed, a faint musty smell in your house can linger for a few days. Sprinkle baking soda on carpets and upholstery, leave it for a few hours, then vacuum. Similarly, small bowls of baking soda or activated charcoal in closets absorb lingering odor.
Why air fresheners won’t fix it
Candles, plug-ins and sprays only cover a musty smell in your house for a few hours. Meanwhile, the growth producing it keeps spreading on the back of that wardrobe or under the sink. In other words, use fragrance after the cleanup if you like it, never instead of one.
When a musty smell in your house needs a professional
- The musty smell in your house is back within a few days of a thorough clean
- Mold covers more than about 10 square feet (roughly 1 square meter), the size the EPA uses as a cut-off for DIY cleanup
- You suspect water behind walls, under floors or above ceilings, or the house has had a leak or flood
- The odor comes from heating or air-conditioning vents
- Someone at home has asthma, allergies or breathing problems that seem worse indoors
Your next step
Pick up a hygrometer, do the sniff test tonight, and then deal with the worst room first. Most of the time a musty smell in your house comes down to one or two damp spots, and once those are dry the air clears within a week.
