Black Mold vs. Other Mold: What the Color Does Not Tell You

Stachybotrys chartarum is a dark mold that prefers cellulose — paper, drywall face, fiberboard — that has stayed wet. It does not sprinkle itself onto dry tile overnight. Other molds are black, green, or gray and grow on wood, stone, and dust. Your eyes cannot sort them. A tape lift can, if a name would change a decision.

Most of the time the decision does not change. Active growth on building materials indoors should be removed and the water stopped, whatever the genus. The name matters more when a buyer, insurer, or physician has asked for it.

Damp buildings irritate some people: stuffy nose, cough, worse asthma, irritated eyes. That pattern shows up with many molds and with the dust of a bad demolition, not only with one famous species. We are not doctors and a spore count is not a diagnosis. If someone is sick, they need a clinician. If the wall is wet, they need the wall fixed either way.

Do not 'test' by disturbing a patch to see if it smears. That is how you put material into the air the furnace will share. Photograph it, keep the door closed, and call.

Bleach is mostly water. On a porous wall it wets the cavity, lightens the surface, and leaves the roots of the problem in the paper. On stone it can create a pale streak that still blooms when the humidity returns. Detergent and drying beat bleach for a small hard-surface spot. Anything larger, or anything on drywall, is a removal job.

Foggers and essential oils do not dry a joist. If the quote you received is a spray and a prayer, get a second one that lists containment and materials.