Mold Growth on Building Materials: What Causes It and How to Stop It
How Much Moisture Is Too Much?
A moisture meter can help identify areas that may need further investigation. For wood building materials, these readings are useful as general guidelines:- 0–15%: Generally dry
- 16–19%: Elevated—monitor closely
- 20%+: High moisture; investigate the source
- 28%+: Increased risk of wood decay if moisture persists
Common Signs of a Moisture Problem
Look for:
- Dark or discolored areas on ceilings or walls
- Musty odors in the attic
- Damp or stained roof sheathing
- Soft, swollen, or deteriorating drywall
- Water stains that return after rain
- Condensation or excessive attic humidity
What Can Homeowners Do?
If you suspect moisture or mold, start with these simple steps:- Find the source. Check your roof, attic, gutters, plumbing, windows, and exterior walls for signs of water intrusion.
- Check moisture levels. A basic moisture meter can help you compare a suspected wet area with a known dry area.
- Stop the water. Repair the leak or moisture source before cleaning or covering the affected material.
- Dry the area. Fans and dehumidifiers can help with drying when appropriate. Avoid closing up wet drywall or wood.
- Don’t simply paint over stains. Painting may hide the problem temporarily, but it won’t stop an active leak or ongoing moisture.
