Black mold: what it is and when to call someone

Colour is not a species and not a risk rating. What Stachybotrys actually is, and the sensible threshold for calling a professional.

"Black mold" is the search term most people use when they are frightened. It usually refers to Stachybotrys chartarum, a slow-growing greenish-black mold that likes very wet cellulose: the paper facing on drywall, ceiling tiles, wet cardboard. It shows up after a leak that has gone unnoticed for weeks, not after a damp weekend.

Is it more dangerous?

Stachybotrys can produce mycotoxins, and it has a reputation that outruns the evidence. The practical position taken by the CDC and EPA is that all indoor mold should be removed regardless of species, that colour is not a reliable guide to which species you have, and that the health effects most people experience (allergy-type symptoms, asthma flare-ups) are caused by many common molds, not just the black one. Treat any significant growth the same way: find the water, remove the material, clean, verify.

What to do when you find it

1. Do not disturb it. Scrubbing or scraping dry mold sends spores into the air. Leave it alone until you have a plan.
2. Find the water. Black mold on drywall almost always means a leak behind it: a pipe, a window, a roof, or condensation on a cold wall. The remediation will not hold if this is not fixed.
3. Judge the size. Under about ten square feet on a hard surface, with the water source fixed, is usually a DIY job with detergent and gloves. Anything on drywall, insulation or carpet, or anything larger, is a professional job because the material has to come out.
4. Get a written quote. See what remediation costs for what it should contain.
5. Consider a test. A lab test tells you the species, which matters mostly for an insurance claim or a house sale. It is not needed to justify removing visible mold.

Common Gettysburg scenarios

• Behind a basement wall in an older borough house with a stone foundation: moisture wicks through the wall, the finished drywall in front of it stays wet, and Stachybotrys grows on the back where nobody sees it. The smell is the first sign.
• Around a window in a newer house where the flashing failed. The stain on the sill is the visible part; the framing behind it is the job.
• Ceiling below a bathroom after a slow tub or toilet seal leak.

When to leave the house

Rarely. People with asthma, severe allergies or compromised immune systems should stay out of the affected area during the work. Everyone else can normally stay in the house while a contained job is done in a basement or a single room.

Last updated 2026-09-28. General information for the Gettysburg area, not professional advice; confirm specifics with a qualified contractor or your insurer.