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Proper foundation drainage is an important consideration for homeowners. Regardless of the type and reliability of waterproofing you apply to your foundation, if there are problems with the drainage, water can easily overwhelm the foundation, leaving the basement or crawlspace wet.
In addition to direct precipitation, there are two other ways that water affects the foundation. Underground water, seeping into the area against the foundation, and runoff from the roof both contribute more water than many people realize, and can often be the reason for a damp basement. Proper foundation drainage is relatively straightforward, and something most homeowners can complete on their own.
The first step in improving foundation drainage is to take time to properly slope the ground around the home so that the soil slopes away from the foundation. This will carry water away from the foundation, where it can then drain into the soil. The proper finished grade for the area around the home is between ½ inch and 1 inch per foot (1.27 and 2.54 centimeters per 30 centimeters meters), extending away from the home for at least 6 feet (1.82 meters), and preferably ten (3.05 meters).
Once the slope is completed, firmly compact the soil with a mechanical compactor. This will press the soil down, and it will be less likely to shift. Without compacting the soil, it is possible for the force of water runoff, and the changing rate of settling, to result in a negative grade, when this happens, water will drain back to the foundation of the home.
The type of soil that is around the house has an impact on the foundation drainage as well. Soil that is heavily composed of gravel or sand will drain quickly, leaving little time for water to pool in the area. Soil that is heavily composed of clay or other silts will hold onto water and drain slowly, which can lead to water pooling against the foundation underground. Long-term exposure to water can cause the foundation to eventually leak and crack. There is no easy way to change the basic composition of soil, but if the soil is composed of slow draining material, pay extra attention to other aspects of drainage.
Most houses have gutters installed, but that is not enough for adequate foundation drainage. A typical gutter and downspout combination will lead water directly from the roof to the area right beside the foundation. There are two ways to move water away from the foundation with this arrangement. Either use an extension at the base of the downspout, approximately 10 feet long (3.05 meters), that will carry the water away from the foundation, and downhill, so that it does not drain back to the foundation, or install a catch basin.
A catch basin is a concrete basin buried at the point where the downspout ends. Fill the basin with crushed stone, and attach an underground drainpipe that comes out from the side of the basin. That pipe runs to an above ground drainage ditch or empties into a drywell.
Taking measures to divert water away from the foundation of your home is the best way to improve drainage. Other methods may provide some relief, but are not generally as effective. Measures such as planting foundation plants to help absorb the water, provide some success, but the most efficient way to keep the basement and foundation dry is to reduce the amount of water around the home.
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