Did you know that a 1" rainfall results in 623 gallons of water per 1000 square feet of roof? Controlling water above ground can prevent water from getting into your basement. Routing water away from the foundation is the first step in preventing basement wetness problems. Making sure that your gutters and downspouts are clear of debris will ensure that they are functioning properly. Extensions on the downspouts will move water away from the structure.
Just like your roof is sloped to shed water, the soil and any driveway/patio slabs around your foundation should be sloped for the same reason. The soil, and sometimes slabs next to the foundation often settles after a home is built. This causes the water that hits the side of the house to run toward and settle against the foundation. Soils that are saturated with water will increase the soil pressure on the basement walls, which can lead to basement wetness, cracks, shifts, bowing and other potential structural problems.
A minimum of 2 inches rise to every 6 feet of run will help to divert water away from the foundation. In some cases it is necessary to place impermeable sheeting under the soils or decorative material near the foundation.
Make sure that window wells are constructed correctly, with drains linked to the foundation drains. Soil elevation in the window well should be several inches below the bottom of the window and sloped to the drain. A drainpipe filled with gravel is a common way to create the drain.
Most home inspectors find that the dampness in basements can usually be traced back to lack of gutters and downspouts and/or poor drainage at the foundation. By correcting above-ground problems you can help to prevent structural damage to your home, as well as dry up those basement damp spots.