Mold on walls can have different causes. In some cases, it is related to condensation from humid indoor air, while in others it may be caused by leaks, insulation problems, rising damp, or moisture coming through the masonry.
Before using bleach or mold-control products, it is helpful to determine where the moisture is coming from. A simple home test using aluminum foil can provide an initial clue.
How the Aluminum Foil Test Works
The principle is very simple: place a piece of aluminum foil directly against the affected area of the wall, making sure it adheres closely to the surface.
Choose a representative area and secure the foil firmly around the edges so that as little air as possible can reach the space behind it.
Leave the foil in place for several hours, preferably around 24 hours. Then carefully remove it and observe where the moisture has accumulated.
