Indoor Moisture

Moisture problems in your home can lead to mold growth, pests (such as cockroaches and rodents) and structural damage. These conditions may cause eye and throat irritation, a runny or stuffy nose, and breathing problems including worsening of asthma.

If you experience any of these symptoms, please call your health care provider.

Signs of a Problem

Signs of a moisture problem inside the home include:

  • Water leaks and stains on walls
  • Water or dampness on windows and other cool surfaces
  • Mold and mildew growth
  • A musty, earthy or stale odor
  • Swollen or warped walls or floors
  • Peeling or bubbling paint

Sources of Indoor Moisture

Many issues can increase moisture inside the home, including:

  • Leaky roofs, windows and pipes
  • High indoor humidity (above 60%)
  • Gutters that drain too close to the home
  • Water build-up around the base of the building
  • Faulty air conditioning
  • Floods or sewer backups
  • Improperly vented clothes dryers
  • Improperly used humidifiers
  • Cooking without proper ventilation
  • Showering without proper ventilation

If you notice any of these signs, try to find the source of the moisture and fix it as soon as possible. If you rent your home, talk to your building owner or manager.


You can protect your home and help keep your family healthy by taking the following steps:

  • Ventilate areas that get wet and damp, such as bathrooms, kitchens, basements or crawlspaces. Open windows or use exhaust fans that vent to the outside.

  • Control humidity levels in your home. A dehumidifier or an air conditioner can help lower humidity levels. You can monitor humidity levels with a humidity detector, which you can buy from a hardware store.

  • If you own your home, check the outside of the home for any leaks or cracks where water can enter. Fix any leaks in the roof, walls or plumbing promptly. Also, check gutters and down spouts to make sure that they are working properly, and check that water drains away from your home.

  • If you rent or live in a multi-unit building, talk to the owner/building manager about fixing the leaks and cracks inside your home. If they do not fix the problem, call 311.

  • Vent appliances that create moisture, such as dryers, to the outside.

  • When cooking, use kitchen range hoods and exhaust fans, or open windows to let in fresh air.

  • If you experience flooding, clean, disinfect and dry out your home as quickly as possible.

  • Install double-glazed windows to reduce condensation.

  • Avoid using carpets in rooms or areas that may have a lot of moisture, such as bathrooms and basements.

  • Learn how to safely clean mold.

Additional Resources

More Information