A wet basement is a catastrophe waiting to happen. Dampness in the confined space of a basement creates a prime environment for the growth of harmful mold, and invites wood-boring insects into the house that can destroy it from within. Unchecked, the wetness will ultimately infiltrate plaster, wallboard, and flooring upstairs.
Solving a moisture problem in the basement may be as straightforward as repositioning a gutter that doesn’t drain properly, or as complex as installing a high-tech dehumidification system. The best approach is to remove or control the source of the moisture, not to try to stop it at the last line of defense.
A floor that’s constantly or seasonally wet is a sign that water is seeping through porous materials in the walls or floor. To check for moisture in a basement, lay a 3' x 3' square of clear plastic sheeting on the floor, then tape down all the edges or secure them with bricks. If water condenses under the plastic, the moisture is coming from a source beneath the floor (rising damp). If water condenses on top of the plastic, the moisture is present in the air.
Sources of humid air include seepage from rainwater that isn’t effectively channeled away from the foundation, and lack of ventilation. In the first instance, check the gutters, downspouts, and leaders to make sure they are conducting water away from the foundation, not toward it. Next, check that the grading at ground level isn’t directing runoff toward the house. If it is, you may need to re-grade some areas so that ground levels slope away from the foundation. (Swales, for instance, can dip as little as 1" to 2" across a 4' or 5' area and still effectively channel water away from the foundation.)
In some cases, footing drains—perforated pipes installed underground around the perimeter of the foundation—may be required. Footing drains catch rainwater seepage and can lower the immediate groundwater level around the building. For best results, waterproof the foundation wall at the same time.
Increase air circulation by adding vents, fans, and dehumidifiers as needed. Generally, no one solution is sufficient to keep water out of the basement. It’s normal to use several techniques and products to reduce wetness, moisture, and humid air.
RIGHT Flaking paint, stained or cracked brick, and ponding water at ground level are all indicators of water penetration into the house and basement.