What Causes Black Areas on Ceilings?

Mold and Moisture

Even though mold spores persist practically everywhere indoors and out, it's only when they land on a moist surface that an actual colony can form. The most important growth condition a mold colony needs is moisture, meaning there are many areas inside your home that can quickly become an ideal breeding ground for mold. Any indoor place with the potential to introduce excess moisture can be a likely habitat for mold. Basements with leaky plumbing, a malfunctioning air conditioner and leaky bathroom and kitchen faucets are examples of these favorable habitats.

Thus, if mold colonies break out on your ceiling, it could be an indication that a central air conditioning component, plumbing or the roof itself is leaky and introducing excess moisture to your ceiling. Mold colonies may appear "cottony, velvety, rough or leathery" and can be "white, gray, brown, black, yellow or green," according to the Florida Department of Health. Mold colonies may also be accompanied by a musty or mildewy odor. Mold that grows on ceilings often remains hidden while growing inside ceiling tiles, so if a black mold colony has broken out on your ceiling it may indicate that the colony has been there for some time and has grown extensively on the inside of the ceiling tiles.

Regardless of where indoor molds occur, removal always involves two steps. First, remove the mold colony using a bleach solution or commercial disinfectant. You may need to use an abrasive scrubber or scrape off the mold and then disinfect the area. If ceiling mold growth is too pervasive, the ceiling itself may need to be replaced. The second step involves eliminating the source of moisture that attracted mold growth on your ceiling in the first place. Removing mold colonies unavoidably involves dislodging the microscopic spores that the colonies produce. Should those spores settle on the same moist surface that they had originally landed on, a new colony will quickly form. Therefore, identify the source of excess moisture on or near your ceiling and remove it or repair it.

A particular group of mold species known as Stachybotrys chartarum is often colloquially referred to as "black mold," though simply because a mold is black does not necessarily mean that it is Stachybotrys chartarum. There is a great deal of concern among homeowners over Stachybotrys chartarum, since these species are capable or producing compounds known as mycotoxins that can cause potentially serious health problems in humans and animals. But it is notoriously difficult to identify a mold species by visual inspection alone, so the more preferable option is always to err on the side of caution by removing any mold growth you find in your home and doing what you can to prevent future mold growth.