The photos above were taken during a home inspection in Aurora Colorado by my company, Magpie Property Inspections. They were taken in a basement wall area where there was a prior issue with moisture intrusion and it looked like the dark material on the drywall might be mold or some type of bio-growth. In this case, we reported the situation to our client and a qualified professional environmental testing expert was brought in to take samples and evaluate the material. It turned out to be a common but serious type of indoor mold, Stachybotrys chartarum, which can be a health concern and cause allergic symptoms in many people and more severe reactions for some people. A remediation company was brought in to remove the affected material and clean the area. The source of the moisture which caused the growth of the Stachybotrys chartarum, was a slightly leaking washer hose on the wall on the other side which had seeped moisture onto the floor and walls over a period of time.
If you see the type of material pictured above, or something like example below of bio growth growing behind a shower wall, it is important to bring in a qualified remediation contractor for the appropriate testing and clean up of all affected areas for the health of the occupants of your home.