A dry basement for work, hobbies, storage, and extra living space is an asset to any home. On the other hand, a wet, damp, musty basement taints the value of the entire house as an investment, and is a source of continuing annoyance and frustration for a homeowner.
The best general advice to anyone attempting to eliminate unwanted water from a basement is that all cures and options should be fully researched.
A homeowner who examines the full range of possible causes and potential remedies will be far more likely to obtain effective and lasting repairs than one who settles for the first, easiest, or least expensive method proposed as a solution.
Look For Obvious Solutions
The cause of a wet or damp basement can be minor, readily apparent, and easily corrected. Here are some probable causes and possible solutions:
Problem: The source of water in the basement can not be identified.
Solution: To determine whether the water is seeping in from the outside or condensing inside, tape a twelve-inch square of aluminum foil to a wall that is prone to dampness, sealing all four sides as airtight as possible. In a day or two, if the side of the foil that was against the wall is wet, the problem is seepage. If the outside is wet, it's condensation.
Problem: Lawns that are flat or slope toward the house permit surface water (rain and melting snow) to drain down against basement walls. Water enters through cracks or other openings in the walls and causes wet spots on the walls or standing water on the floor.
Solution: Slope the ground away from the outside foundation (about one inch per foot) with tamped dirt, not mulch. Mulch can harbor termites if extended above the foundation line. Extend the slope for at least ten feet. Seed it with a good lawn grass. Sodding is a common practice and prevents the washing away of newly graded areas during heavy rains.
Where a large area of land slopes toward the house, surface drainage should be intercepted and redirected some distance from the house. Dig a shallow, half-round drainage ditch or depression designed to route the water around the house. Sod the ditch or plant grass in it. If even a shallow ditch is objectionable, drainage tiles, with one or more catch basins at low spots, may be installed.
Problem: Defective, clogged, or nonexistent gutters and downspouts allow roof water to form puddles, or wet soil near or against basement walls, and enter through cracks or openings in the masonry.
Solution: Install gutters and downspouts wherever needed. Keep them free of debris. Where leaves and twigs from nearby trees may collect in a gutter, place aluminum screening across the length of the gutter. Repair gutters and downspouts as soon as the need appears. To prevent concentration of water at the point of discharge, consider extending downspouts through underground piping away from the outside foundation to a storm drain, dry well, or surface outlet fifteen feet or more from the house.
Problem: Dense shrubbery and other plantings around the basement walls prevent good ventilation.
Solution: Trim heavy growths of shrubbery so that soil gets more sunlight and dries quicker. When digging up the plantings, remove any pieces of masonry, mortar, or other material buried near the house after the basement was excavated.
Problem: Unprotected basement window wells act like cisterns during heavy storms, permitting water to seep in around window frames and below windows.
Solution: Windows or parts of windows below grade should be protected by metal or masonry window wells, with bottoms consisting of gravel to permit good drainage. These wells can become a drainage point for foundation saturation through the sides of the well. Clear plastic bubbles are available to cover the entire window well like an awning but can sometimes redirect the water down through the sides of the well.
Problem: Atmospheric moisture produces condensation ("sweating") on cool surfaces in the basement, particularly walls, floors, and cold water pipes.
Solution: Insulating the water pipes can help but condensation may still occur. Promote good ventilation--sunlight and free movement of air can quickly dry out a basement. Ventilation should be regulated according to the weather conditions. During hot, humid weather or long rainy spells, windows should be closed because the outside air will probably contain more moisture than the basement air. Heat the basement during the winter. During hot weather, use air conditioning to cool and dehumidify the air.
Problem: Leaky plumbing or other sources of moisture--such as clothes hung to dry on basement lines--increase humidity in the air, causing condensation.
Solution: Repair plumbing promptly, open windows or dry clothes in an automatic dryer vented to the outdoors. If the problem persists, experiment with using a large-capacity dehumidifier to eliminate condensation, be sure it is an adequately sized dehumidifier for the square footage of the area. Try borrowing one from a friend or neighbor before investing in what may turn out to be the wrong remedy.