Mold needs moisture. Cleaning visible growth without fixing the moisture source is a temporary fix. This guide covers the common sources and the habits that keep them under control.
Find the moisture source
Common sources include roof leaks, plumbing drips, condensation, high indoor humidity, crawl space moisture, and water intrusion around windows and doors. Sometimes the source is a combination of small issues.
Look for water stains, bubbling paint, soft wood, musty odors, and condensation on windows or cold surfaces. A moisture meter can help confirm damp materials.
Ventilate bathrooms, kitchens, and laundry
Run the exhaust fan during and after showers and cooking. Make sure the fan vents outside, not into the attic. Keep dryer vents clean and check that they discharge outdoors.
Use a dehumidifier in damp basements or crawl spaces when needed. Do not block foundation vents or HVAC returns.
Keep indoor humidity in check
A hygrometer can tell you the indoor humidity level. In many climates, keeping it below the high range reduces condensation and mold risk. Use air conditioning, dehumidification, and ventilation together.
Fix leaks promptly, even small ones. A slow drip behind a cabinet can create mold long before it causes visible damage.
When to call a professional
- Mold covers a large area or keeps returning.
- The moisture source is hidden or difficult to access.
- Mold is in HVAC ductwork or crawl spaces.
- You have health concerns or a compromised immune system.
- Water damage affected drywall, insulation, or structural materials.
A remediation professional should explain containment, removal, drying, and verification — not just spray the visible area.
Frequently asked questions
Does bleach kill mold?
Bleach can clean some surfaces, but it does not fix the moisture source and may not reach porous materials. Removal and drying are often necessary.
Can mold grow in winter?
Yes. Indoor humidity, condensation, and leaks can support mold growth even when it is cold outside.
Do I need a mold test?
Testing can confirm the presence and type of mold, but the moisture source still needs to be fixed. A professional can advise whether testing is useful.
Need help now? Call (877) 471-2907 and describe the situation. The line is open 7am–10pm EST, seven days a week. For a gas leak, fire, or life-threatening emergency, call 911 first.
About this guide: This information is general and educational. It is not a substitute for an on-site assessment, a licensed professional's advice, or your local building code. Verify licensing and insurance directly with any provider you hire.