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Mold on drywall
Drywall is paper over gypsum, and mold eats paper. What you see on the painted side is often the smaller half.
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The short version
- Small surface patch
- Under about 10 square feet, the EPA says most people can handle it.
- Soft or stained through
- The drywall is replaced, not cleaned.
- Call a company when
- The patch is large, keeps returning or follows a leak inside the wall.
Signs it is on the surface
- A small patch in a bathroom or behind furniture.
- The drywall is firm when pressed.
- No leak in or behind the wall.
- It appeared with condensation, not a leak.
Signs it goes deeper
- The drywall is soft, swollen or crumbling.
- The stain follows a plumbing line or a roof leak.
- It returned after cleaning.
- There is a musty smell with little visible.
What the EPA says
- SizeBelow about 10 square feet you can usually handle it yourself; above that, use a professional or EPA's remediation guidance.
- The back sideMold may be "hidden in places such as the back side of dry wall." If you suspect that, consider an experienced professional.
- The waterClean up the mold and fix the water problem, or it comes back.
- Cleaning products"Never mix chlorine bleach solution with other cleaning solutions or detergents that contain ammonia."
What a mold company will do
- Find the moisture source and measure how far it has spread.
- Contain the area.
- Cut out drywall that cannot be saved and check the framing behind it.
- Dry the cavity before anything is closed up.
Painting over mold does not stop it. It grows through, and the wall behind stays wet.
Related guides
Mold remediation: what drives the cost
Mold testing: when it is worth paying forSources
- US Environmental Protection Agency: mold, moisture and your home