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What causes a musty smelling house?

A musty odor in your home can be annoying and concerning. This smell is often described as moldy, damp, or stale. While a musty smell is rarely dangerous, it usually indicates an underlying issue that needs attention. Here are some common causes of a musty odor in homes and tips for removing the smell.

Excess moisture

Excess moisture is one of the most common causes of a musty smell in a home. When moisture builds up indoors, it can lead to mold and mildew growth, which gives off a distinctive musty or earthy odor. Sources of excess moisture include:

  • Leaks or water damage from plumbing, roofs, windows, etc.
  • High indoor humidity
  • Lack of proper ventilation in bathrooms, basements, and attics
  • Condensation on cold surfaces like windows and pipes

Fixing leaks, improving ventilation, using a dehumidifier, and addressing condensation issues can all help reduce indoor moisture and musty smells.

Dirty or faulty HVAC system

Problems with your home’s heating, ventilation and air conditioning (HVAC) system can also cause musty odors. Dust, dirt, mold, and mildew can build up and get circulated through the ductwork. A cracked heat exchanger or drain pan issues can also contribute to smells. Having an HVAC professional inspect and clean your system can eliminate musty odors.

Carpet and furniture

Carpeting, upholstered furniture, rugs, and other soft furnishings can hold onto musty smells easily. Damp basements or excess moisture that gets absorbed into these materials can lead to lingering odors. Vacuuming and cleaning with an enzyme cleaner designed for pet odors can help remove musty smells from carpets and upholstered items.

Washer and dryer

If your washing machine isn’t draining properly or clothes aren’t getting fully dried in the dryer, they can take on a persistent musty or mildewy smell. Run empty cycles with bleach or vinegar to disinfect the washer. Clean out the dryer vent and make sure the outdoor vent flap opens properly so moist air isn’t trapped inside.

Garbage and food waste

Letting garbage and food waste pile up can also contribute to musty smells. Be diligent about taking out the trash regularly. Keep food scraps contained and promptly clean up any spills. Compost outdoor if possible.

Pets and their accidents

Pets and their accidents can be a source of musty odors, especially if urine isn’t promptly and properly cleaned. Use an enzyme cleaner formulated to eliminate pet odors rather than just masking them. Clean carpets, floors, kennels, litter boxes, and anywhere else regularly.

Smoking indoors

Cigarette, cigar and pipe smoke can lead to persistent musty odors sinking into carpets, walls, furniture and window treatments. Stop smoking indoors and thoroughly clean soft furnishings to eliminate odors.

Old books or newspapers

The musty smell of old books, newspapers and other paper products is caused by mold and mildew growth. Store these items in a clean, dry area to prevent odor. Discard water damaged or smelly books and papers.

Dirty or musty basement, attic or crawlspace

Neglected basements, attics and crawlspaces are prone to moisture accumulation which leads to musty odors throughout the home. Improve ventilation, repair leaks, install moisture barriers, and add exhaust fans to address musty smells in these commonly problematic areas.

How to get rid of musty smells

Once you’ve identified and addressed the source of the musty odor, here are some tips to help eliminate lingering smells:

  • Open windows to air out the home.
  • Run fans and dehumidifiers to remove excess moisture.
  • Shampoo or steam clean carpeting, rugs and upholstery.
  • Wash walls, floors and other surfaces with bleach, vinegar or enzymatic cleaners.
  • Paint walls with mildew resistant paint.
  • Replace insulation or porous materials with persistent musty odors.
  • Use baking soda or charcoal air purifiers to absorb odors.
  • Add moisture absorbing products like DampRid to closets and basement.

Preventing excess moisture buildup and properly ventilating damp areas of your home are the keys to avoiding a musty smell long-term.

When to call a professional

DIY solutions may be effective for minor musty odor issues. However, if smells persist despite your best efforts, it may be time to call in a professional. Water damage restoration companies specialize in locating and remediating moisture issues. A home inspector can check for leaks, ventilation problems and signs of mold throughout the home. HVAC companies can inspect ductwork and address any issues causing odors to spread. Don’t ignore a stubborn musty smell in your home – the underlying cause will only get worse over time if not properly addressed.

Health concerns related to musty odors

In rare cases, persistent musty odors may indicate a more serious indoor air quality issue. Some potential health concerns include:

  • Mold exposure – Inhaling mold spores can cause allergic reactions and respiratory issues in some people.
  • Bacteria and pathogens – Damp areas allow growth of bacteria and pathogens that can cause illness.
  • Dust mites – Musty smells signal excess moisture where dust mites thrive.
  • VOCs – Mold and mildew release potentially harmful volatile organic compounds (VOCs).

Have your home’s air quality tested if musty odors coincide with health issues. Wear protective gear when cleaning moldy areas. See a doctor if you have respiratory trouble that correlates with exposure to musty smells.


A musty, moldy odor in your home is typically a sign excess moisture is present and needs to be addressed. Common causes include leaks, high humidity, condensation issues, carpet and fabrics holding odors, dirty vents, and forgotten trash. Improve ventilation and reduce moisture to eliminate musty smells at the source. Thoroughly clean any moldy or smelly areas and consider replacing porous materials with stubborn odors. Call in professionals to fully inspect and remediate if DIY efforts don’t eliminate the smell. With some diligent detective work and prompt action, you can successfully banish musty odors from your home for good.