Mold vs. Mildew: Understanding the Differences & Moisture Risks
Not sure whether that black spot in your bathroom is mold or mildew? You’re not alone. While both are types of fungi caused by moisture, knowing the difference can help you respond properly and avoid future problems.
At Purisync Heating and Air, we help Missouri homeowners identify and prevent all types of indoor moisture issues. Here’s how to tell mold and mildew apart — and what to do if you find either.
What Is Mold?
Mold is a fungus that grows in damp, warm, and dark environments. It often appears green, black, or brown and grows in fuzzy, patchy patterns. Mold can penetrate porous surfaces like drywall, wood, and carpet — and it can cause serious structural and health problems if left untreated.
What Is Mildew?
Mildew is a surface-level fungus, usually gray or white, with a powdery or flat appearance. It tends to grow on non-porous, moist surfaces like tiles, shower walls, or windowsills. Mildew is typically easier to clean than mold but still indicates a moisture problem.
Key Differences Between Mold and Mildew
| Feature | Mold | Mildew |
|---|---|---|
| Color | Black, green, brown | White, gray, light yellow |
| Texture | Fuzzy, slimy, irregular | Powdery or flat |
| Depth | Penetrates surfaces | Surface-level |
| Odor | Strong, musty | Mild, musty |
| Health Risk | Moderate to high | Low to moderate |
Where Mold and Mildew Grow in Missouri Homes
- Mold: Under flooring, behind walls, in basements, HVAC systems, and after leaks or water damage
- Mildew: Bathroom tiles, windows, shower curtains, kitchen backsplashes, poorly ventilated areas
How to Prevent Both Mold and Mildew
- Keep indoor humidity between 30%–50% (use a dehumidifier)
- Ventilate high-moisture areas like bathrooms and kitchens
- Fix leaks quickly — especially under sinks, behind appliances, or in basements
- Clean and dry wet surfaces within 24–48 hours
- Inspect hidden areas if you smell mustiness (see our moisture inspection guide)
When to Call a Professional
If the growth:
- Is larger than 10 square feet
- Keeps returning after cleaning
- Appears on porous materials (drywall, insulation, etc.)
- Causes health symptoms indoors
It’s time to call Purisync for professional inspection and removal.
Serving Missouri Homes with Moisture Solutions
We proudly serve:
Call (314) 338-5111 or book an inspection to keep your home dry, clean, and safe year-round.
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