Here is a very interesting article, courtesy of "A Buyers Choice Home Inspections" regarding Moisture Problems:
Detecting moisture in walls, foundations and floors is a vital part of any home inspection. What many home buyers do not understand is that the moisture problems not only come from the rain outside the home, but they can be generated from inside the home. Bathrooms, laundry rooms, kitchens and attics are the areas of the home where moisture is normally a concern.
The bathroom tub surround, shower and the sink backsplash are constantly exposed to water. These water protective surfaces can break down and cause damage to the walls behind. Another area of concern is the wax seal under the toilet. This wax seal keeps the toilet water from leaking out as it passes into the sewage pipe. If this wax seal breaks down, water will seep out and be absorbed by the wooden flooring material. This will cause rot and instability in the toilet. It can even cause leaks and damage to the ceiling in the room below the bathroom.
The kitchen and the bathroom have exhaust fans to remove moist air and odours from the house. Normally the room air is exhausted into a flexible vent pipe that travels through the attic and out of the house through a roof mounted vent. Sometimes these flexible vent pipes fall off of the roof vents. And sometimes people don’t even install a roof vent! They just exhaust the moist air into the attic. When either of these things happen the moisture level in the attic sky rockets and this can lead to mold growth, air quality problems and health hazards in the home.