It is common to find medicine cabinets set into the walls of homes. They should not be installed in the exterior walls of the home however—especially if it is an older home with only 2×4 walls. It is very difficult to get enough insulation—if any—behind the unit to prevent the back of the cabinet from being much cooler than the rest of the walls in the bathroom.
Cooler walls means more condensation.
Moist bathroom air that finds its way into the cabinet will condense on the cooler surface and create an ideal environment for MOLD growth. This picture is a good example of this condition. In this case the best solution would be to install a cabinet on an interior wall—-and throw away this one.
While it might be OK to have penecillin in the medicine cabinet—this kind of mold we can do without.
Charles Buell, Seattle Home Inspector
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