What This Checklist Is For
Mold needs a comfortable environment, food, and moisture to take hold, and a home that has been sealed or insulated without enough attention to ventilation is exactly the kind of environment that lets it grow. Left undetected, mold can lead to allergic reactions, respiratory infections, and other health problems. Use this checklist to inspect your home for the warning signs that a retrofit went wrong somewhere and moisture is building up where it should not be.
Before You Start
When you go looking for the source of a moisture problem, you may disturb a contaminated area and spread it further into the rest of the home. That is a real health risk for anyone with a compromised immune system, asthma, or allergies. Consider talking to your doctor or hiring a professional before starting a thorough investigation, and if you do search it yourself, wear appropriate personal protective equipment.
Basement and Crawl Space
- Inspect the ceiling, joists, and stairs for mold growth.
- Check the indoor humidity level with a moisture meter or humidistat. Humidity should stay below 60 percent, and the optimal range is between 30 and 50 percent. If it climbs above 60 percent, consider running a dehumidifier, and empty and clean its drip pan regularly.
- Watch for peeling paint, imperfections, or discoloration, since these can indicate moisture. If you find any, locate the source, eliminate it, and dry the area within 24 to 48 hours.
- Inspect the floor for foundation cracks, checking both inside and outside, since a crack can run through to the exterior.
- Check that the sump pump is functioning properly and the floor drain is intact.
- Inspect the crawl space for moisture leaks and confirm it is properly sealed. At a minimum there should be a vapor barrier, 6 to 8 mils of plastic, covering the soil.
Exterior and Yard
- Make sure gutters and downspouts are intact, free of debris, and directing water away from the house. Downspouts should extend 6 to 10 feet from the foundation.
- Look for water pooling on the roof or around the foundation, a sign that water is not draining properly.
- Check that the ground slopes away from the house, about 6 inches over 6 to 10 feet, to direct water away from the foundation.
- Inspect the siding and exterior paint for peeling, chipping, or bubbling, and look for visible mold growing on the house itself.
- Inspect the roof for missing or curling shingles that could lead to indoor leaks.
- Check that flashing around doors, windows, joints, and chimneys is in good condition.
- Make sure the outside dryer vent is not blocked and that it vents outdoors rather than into a crawlspace, attic, or other indoor space.
- Make sure sprinklers spray only the grass, not the house.
- Check that plantings near the foundation are not overwatered, and remove them if there are too many.
Floors, Ceilings, Windows, and Walls
- Inspect ceilings and walls for discoloration, sagging, bowing, or wet spots, and lift any dropped ceiling tiles to check the cavity above them.
- Check windows and walls for condensation, which can signal high indoor humidity.
- Look for moisture leaks or peeling drywall around window frames.
- If you suspect mold under the carpet, lift a corner and check the underside.
- Check behind vinyl wallpaper for mold.
- Mold in a closet is often a sign of poor ventilation. Leaving the door open, or removing about a third of the closet's contents to improve airflow, can help.
Kitchen and Bathroom
- Inspect caulking, grout, and tile for damage and repair as needed.
- Check for plumbing leaks around sinks, tubs, refrigerators, dishwashers, and showers.
- Test the exhaust fan by holding a sheet of toilet paper in front of it while it runs. If the paper stays in place, the fan is working.
- Confirm kitchen and bathroom fans vent to the outside rather than the garage, attic, or another indoor space.
- Run the bathroom fan, or open a window if there is not one, every time someone showers or bathes.
- Check cabinets, drywall, and wood materials for mold or a musty smell.
- Clean and empty the refrigerator drip pan.
Attic
- Check for moisture damage, leaks, and proper ventilation, making sure exhaust ducts direct air outside.
- Make sure the soffits under the eaves are not blocked, since they provide airflow into the attic.
- Inspect the walls, joists, and insulation for a musty smell or visible mold.
Appliances
- Install a water heater drip pan if you do not already have one, and empty and clean it regularly.
- Have heating and cooling systems serviced by a professional twice a year, and check the coils for visible mold.
- Check water heater and washing machine lines for leaks.
- Make sure the dryer vents outside rather than into the garage, crawlspace, attic, or another indoor space.
Other Signs to Watch For
- Large quantities of houseplants, a large aquarium, hanging laundry to dry indoors, or an unvented heater or gas logs can all add to a home's humidity.
If You Spot a Warning Sign
Anywhere you notice a musty, earthy smell or see excess moisture, mold can take hold. If you find either, act right away. Find the source of the moisture first, fix it, then remove any contaminated material and clean the area with soap and water before drying it quickly. Once the source is fixed, that is usually enough to resolve the problem, without needing to test for mold at all.