While the spring rains may be forgotten, this is a perfect time of year to make sure your basement’s dry next year. First off, how much water should you worry about? Even if you’re not finishing a room or storing anything in your basement, high humidity or standing water can breed unhealthy mold and mildew.
If you are planning on finishing, you want it as dry as possible. Beware of: humidity, which condenses on cold surfaces, and seepage from the outside.
To find out if your humidity’s high, use a hydrometer. 60% in the summer or 50% in the winter is high, and may be caused by an unvented clothes dryer, uninsulated cold-water pipes (which may sweat) and the aforementioned seepage.
Vent the dryer outdoors, insulate those pipes with foam sheathing, and improve ventilation with windows or a fan. A dehumidifier may also help. Continue testing over a few months.
Even if you’ve decreased the humidity, you don’t want a leak from outside to damage your new room.
Start outside. Clean your gutters and test them for leaks. Make sure your downspouts drain into a splash block or extend away from your house at least 18 inches (8 to 10 feet is ideal). The grading should slope away from your house all along the foundation, at least a half inch per foot for the first three feet.
Clear debris from basement door and window sills, and caulk the seals at the bottom of doors and windows.
This outside work could actually cure your problem, but you may need to do some work inside. More on this next time.