Sleuthing for basement moisture
I’d like to finish my basement with wainscot walls; however, the basement is somewhat wet even though the site is graded so that groundwater runs away from the house. I don’t want the construction to rot away in a few years. How can I determine whether my finished basement will last?
James R. Branit, Chicago, IL
Specialist in Housing and Engineering Joseph T. Ponessa of Rutgers Cooperative Extension at New Brunswick, New Jersey, replies: Rainwater is not the only source of basement moisture. There can be a great deal of moisture in the air on a muggy summer day in Chicago. The origin of the moisture problem, or its major source, can help you decide about finishing the basement. Here is a good way to identify the source of moisture in the basement: Tape a couple of 1-ft. squares of plastic sheeting to the wall and to the floors. After several hours, look for condensation. Moisture underneath the plastic indicates a soil source of moisture; wetness on top is due to humid air from outside.
I would expect that, for most of the summer, outdoor air is the major source of basement moisture. For summertime moisture control, an adequately sized dehumidifier may be your only answer. Unless there is a high water table, winter conditions should be somewhat better, especially if a furnace or a boiler is pulling air through the basement. Therefore, I would go ahead with the construction.
If there is a lot of moisture coming through the wall, installing a finish wall may not be a good idea because it will trap the moisture and lead to mold, mildew and rot.