Basements suffer from a special ill that doesn't affect other spaces inside your home. Moisture. Differences between temperature below ground (50 to 60 degrees in summer) and that of the air upstairs or outside often create the potential for a slight mustiness, especially in muggy summer weather. However, if the floor or walls in your basement chronically sweat, or worse yet, if puddles of water collect on the floor, it is time to take action. A wet basement not only wastes potential space for living or storage, it eventually could decay your home's floor joists and sills.

The chart below will explain the four
sources of below-ground moisture
problems. Simple tests help you
distinguish one from the other and
direct you to their remedies. In tracking
down the origin of the water, don't
neglect the possibility that it might be a
combination of factors--condensation
couple with seepage, for example.

If you are planning to finish the basement
walls and floor, you will want to dry them
out permanently before you begin any interior construction work. That may require more costly exterior waterproofing methods. Don't worry about mild condensation; putting up insulation and a vapor barrier usually will eliminate the problem. If you are not sure that this will work in your situation, apply two coats of exterior sealant on the inside of the walls.

Where's the water coming from?
Problem-Condensation.
Symptom/Test-Damp walls, dripping pipes, rusty hardware,mildew. Causes-Excessive humidity in the air, usually from an internal source, or a significant difference in temperature between the wall and the outside air. Solution-Install a dehumidifier, improve ventilation, or insulate the foundation walls

Problem-Seepage.
Symptom/Test-General dampness on the floor or a particular wall, especially near floor level. Tape polyethylene to the wall. If moisture condenses behind it, seepage is the culprit. Cause-Surface water is forcing it's way through the foundation or an expansion joint. Source may be poor roof drainage, a window well, or a clogged drain tile. Solution-Improve surface drainage. An interior sealer may work on minor seepage. If not, waterproof the foundation from the outside.

Problem-Leaks.
Symptom/Test- Localized wetness, oozing, or trickling from a foundation wall or floor. Check the damp area carefully, paying attention to mortar joints between blocks. Cause-Cracks resulting from normal settling or faulty roof drainage, a grade that slopes toward the wall, or a clogged drain tile. Solution-Plug a single hole from the inside. Otherwise, dig down and work from the outside. Waterproof entire foundation wall and install drain tile. Slope grade away from the wall.

Problem-Subterranean water.
Symptom-A barely noticeable film of water on the floor could be a sign. Lay down a sheet of polyethylene for several days; if moisture is penetrating, it will dampen the concrete underneath. Cause-Usually a high water table is forcing up water from below under high pressure, turning you basement into a well. This may happen only during rainy periods. Solution-Drain tiles installed around the perimeter of the foundation or floor may help, but only if connected to a lower spot or a storm sewer. You may need a sump pump.