Damp basements are one of the most common problems that plague homes. This includes old houses and new houses. Many damp basements can be improved simply and inexpensively. It is worth investigating a little yourself before calling in a basement expert.
Surface Water The common cause of damp basements is improper handling of exterior surface water (rain water). Surface water that saturates the soil immediately next to the home can make its way into the basement.
Condensation Condensation is a common problem in basements. Condensation looks and smells like basement leakage. It is sometimes difficult to distinguish between the two. There are a few things you can do to improve the situation. First, try reducing the sources of interior moisture. If there is a shower or bathtub in the basement that is used regularly, make sure there is an exhaust vent and that it gets used. Verify that the clothes dryer vents outside. If the basement is clearly colder than the rest of the house, warm it up. This will reduce the relative humidity and reduce the potential for condensation. One of the most common scenarios is an air conditioned home where the basement is colder than the rest of the house. These basements often smell and feel damp. Reduce the flow of cold air to the basement by closing air registers. Consult with a Heating, Ventilation and Air Conditioning technician to investigate the possibility of adding return air registers to the basement. If you see moisture on the surface of the foundation, you can test if it is water seeping through the foundation or if it is condensation. Tape a piece of clear plastic sheet, about one foot square, tight to the foundation wall. After a few days, see if moisture has formed on top or underneath the plastic. If the moisture is on top, you have a condensation problem.
Dehumidifiers Dehumidifiers sure do work to reduce the moisture in the air and thus tend to dry the basement. However, dehumidifiers use a great deal of energy. Try to deal with the source of the moisture first. Pillar To Post® inspectors have reported seeing many homes with clothes dryers venting gallons of moisture into the basement with dehumidifiers running continuously along side. This is a huge waste of energy!
Basement Floor Drain Basement floor drains should have water in them. This water is a vapor lock that prevents sewer smells from getting into the house. If your basement has a musty smell, check the floor drains. If the drain is dry, pour a bucket of water down the drain. Check it again an hour later to see if the drain keeps its prime. While some problems can be easily solved some dampness problems are more serious. In these situations, an expert will be required.
*Source: Pillar to Post http://www.pillartopost.com/septpostnotes2013#inspectioninsights (retrieved March 2014)