Signs of black mold (and when to worry)

“Black mold” usually means Stachybotrys, a greenish-black mold that grows on chronically damp, porous surfaces. You can’t confirm the species by eye, but a few signs reliably point to a problem worth investigating.

What to look for

• A persistent musty, earthy smell — often the first sign, before you see anything.
• Dark green-to-black patches that look slimy or fuzzy, especially on drywall, ceilings, or around plumbing.
• Water history — a past leak, flood, or condensation problem in the same spot.
• Symptoms that ease when you leave — congestion, cough, or irritation that improves away from home.

Is it actually mold?

Surface stains are sometimes just mildew, which is cheaper and easier to handle — see mold vs mildew to tell them apart.

What removal costs

Black mold costs more to remove than common mold because of containment and disposal. Get a ballpark with the black mold removal cost calculator before you call anyone.