How to treat black mold and when to call a pro?« Back to Previous Page

Black mold in a closet on an interior wall is a common issue here, often caused by high humidity and condensation from AC units creating a damp microclimate. The first step is to remove all items from the closet to assess the full extent and allow the area to dry completely.

For a small patch (under one square meter), you can treat it yourself. Wear an N95 mask and gloves. Clean the visible mold with a solution of detergent and water, then follow with a diluted bleach solution (one part bleach to ten parts water) to disinfect the area. However, this only addresses the surface. The key to stopping regrowth is controlling the moisture source. Use a moisture meter to check the wall's humidity level; anything above 18-20% indicates a persistent dampness issue. Improve air circulation by occasionally leaving the closet door open and consider using a desiccant dehumidifier bag inside.

You should definitely call a professional for inspection and remediation in three scenarios: if the mold covers a large area (generally over one square meter), if it returns after cleaning, or if you suspect it has spread into the wall cavity. A musty odor or warped baseboards are strong indicators of hidden growth. Professionals use thermal imaging and borescopes to see inside walls and lab testing to identify the species, which dictates the correct remediation protocol. DIY methods often fail because they don't address the root moisture problem, and disturbing extensive mold can spread spores throughout your home.