Black mold on wall: DIY fix or call a professional?« Back to Previous Page

That black spotting is classic mold growth, and your description points directly to the two most common causes here: high humidity and a cold surface. The wall facing the garden is likely an exterior wall, and with the recent rains and our high humidity, the temperature difference between the air-conditioned room and the warm, moist outdoor air causes condensation inside the wall cavity. This trapped moisture creates the perfect environment for mold.

For a small, isolated patch (under 1 square meter), a careful DIY approach can work. Wear an N95 mask, gloves, and eye protection. Move the sofa away. Mix a solution of one part white vinegar to four parts water or a diluted bleach solution (1 cup bleach to 1 gallon of water) and scrub the area thoroughly. Let it dry completely. However, this only addresses the surface growth. The critical step is identifying and stopping the moisture source. Check for leaks from the garden irrigation, cracks in the external render, or insufficient external waterproofing. A dehumidifier in that room can help manage ambient humidity.

Given the description of it "spreading," its location on an exterior wall, and the persistent damp feeling, this suggests a more significant moisture issue is likely present within the wall itself. In these cases, surface cleaning is a temporary fix. The mold will almost certainly return unless the underlying condensation or seepage problem is professionally diagnosed and resolved. This often requires moisture meters and thermal imaging to pinpoint the exact entry point. For villas, this is a common and serious issue that usually warrants a professional inspection to prevent structural damage and potential health impacts from recurring mold.