J. WICKING MOISTURE CONDENSATION:
Occasionally a relatively new house will display repeated or continuous condensation around a basement wall/floor area. Usually the moisture on the wall surface will extend up the wall about 8 inches and out on the floor about the same distance (Fig. J1, Item A). This is typical of condensation that forms when the moisture in the air reaches the dew point on the cool basement surfaces. Often, however, this condition persists through periods of low relative humidity in basements and is accompanied by larger circular moisture spots on the floor. When there is a combination of wall/floor condensation and open floor spotting, moisture may be wicking up from the ground (Fig. J1, Item B).
This type of condition is normally associated with seasonal high water table measurements but may also be due to water that has become trapped under the foundation and slab during original construction. It takes a long period of time for such trapped moisture to dry out. There are commercial quality dehumidifiers available to dry out this moisture. They are often used after a house has suffered flooding from a burst pipe, fire fighting, or something similar.
Sometimes the footings of a house are set into the high water table limit of an aquifer beneath a house. When this occurs, moisture can soak the footings and travel upward, contributing to a “condensation” problem around the walls. It is important to understand that moisture trapped beneath a floor slab cannot vaporize easily or quickly due to the plastic under the slab and the slab itself.
WHAT TO: HOW TO:
If wicking moisture is suspected as contributing to a condensation problem within a basement, several minor tests can be conducted to confirm this. Drying a moistened area with paper towels and then air drying it with a hair dryer is the first step. Once the area is dry, aluminum foil is securely taped against the surface and left in place. If moisture beads up beneath the foil, the origin of the moisture is through the concrete or masonry; but if it beads only on the air surface side, condensation from the air is the moisture source. There are also professional diagnostic tools available. The “dew tab” is a foil backed paper treated with a dye that will discolor with condensation. These tabs are placed in suspected areas and are considered definitive when the dye becomes readable. |
