If the water table in your area is above your basement floor, you may be dealing with water seeping into the basement.
Water can get into the basement where the walls and floor meet and through cracks in the floor. Sometimes water also will come through cracks in the wall, but that usually is the result of water soaking into the ground from above.
One way to deal with seepage is to install drain tile or pipe in porous, granular material along the house footing, according to Ken Hellevang, North Dakota State University Extension Service agricultural engineer and flood expert. The drain tile or pipe will create a drainage envelope to intercept the water and direct it to a sump, where it can be pumped outdoors.
Other ways to get rid of the water entering the basement are channelling it from the entry point to a basement drain or removing it using a skimmer pump or wet/dry vacuum.
“Water will continue to enter or try to enter the basement as long as the water table is high, so the goal is to control the water flow rather than eliminate it,” Hellevang says. “Generally, the water cannot be stopped from entering the basement with products placed inside the basement because of the external water pressure.”
Controlling water seepage is important because it can cause a number of problems. A major one is mould growth, which is a health hazard. Wet or damp materials will mould in one to three days, depending on the temperature.
“Mould spores, which are like mould ‘seeds,’ are in the air everywhere, so the only method to prevent mould growth is to keep things dry or to remove them from the damp area,” Hellevang says. “Remove porous materials such as cardboard boxes, papers, carpet, rugs and clothes to keep them from becoming mouldy.”
Chlorine bleach will kill existing mould, but it does not prevent future mould growth. Mould must be removed, not just killed, to eliminate the health hazard.
Seeping water also can damage walls. Many wall coverings are porous and not only will absorb water but will wick, or pull, it above the water level. For example, gypsum board or drywall (Sheetrock) is very absorbent and will wick water up a wall.
Hellevang recommends that if you do have seepage problems, you should remove or cut the gypsum board so none of it will be in the water. Mould grows readily on the paper covering gypsum board, so controlling the humidity level in the basement is critical to minimizing mould growth as well.
Many panelling materials also are absorbent, so you should cut the panelling to above the water level. If the water level is shallow, the wall can be repaired by using a tall baseboard.
Hellevang suggests buying a humidity gauge and keeping the humidity in the basement below 70 per cent. A dehumidifier will remove some water from the air. Ventilating with dry outdoor air also will reduce the humidity level.
Providing openings for air to enter and exit is critical to achieving ventilation. Open at least two windows for cross-ventilation. Using a fan facing to the outdoors will help move dry outside air through the basement. You also should use fans to circulate dry air across damp surfaces to help the material dry.
In addition, you should isolate the basement from the rest of the house to prevent the humidity in the basement from entering other parts of the house.