The most serious problem caused by poor surface drainage around homes is water in the basement. In almost every situation, this problem is caused by the lack of surface water flowing away from your house and other structures. If soil is graded so that storm water flows downhill and away from the foundation of your house, there is a good chance storm water will not flood your home except in the most extreme circumstances. Typical drainage problems can be easily fixed if you take a close look at the slope of your property.
Correcting your drainage problem can be simple. Before considering expensive solutions such as sump pumps, wall excavations, waterproof paints or sophisticated underground drainage systems, inspect the area surrounding your home for low spots.
Generally, my strategy is to ensure you have a downhill slope dropping three to six inches for every 10-foot run. If a grade slopes down and away from your home continuing slightly downhill, your basement will stay dry, and the area should remain well drained and usable for planting or other outdoor activities.
A common cause for poor surface drainage occurs when homeowners install walks or patios on perfectly level surfaces. This causes water to remain on these areas, which in turn encourages fungi and algae growth. Paved surfaces should drop two to three inches over 10 feet. This can vary between a 1.5 to 3 percent grade and will still appear level.
Check the drainage patterns around your house during a storm to make sure that all water rolls away from the downspouts and walls, even if water in the basement is not a problem.
If there is evidence that water is not flowing away from your home, add soil to create a downhill slope along the walls. The fill should have a high percentage of clay in it and be low in rock, sand or compost. Soil within approximately two feet of the wall should have as little organic material as possible in it. This “slope” of soil should direct water downhill, not help percolate it.
Only build soil up against masonry walls, never against siding or wood. Draining away from siding or wood requires removing soil five to 10 feet from the wall of your house and creating a downhill slope from the wall to a dish-shaped drainage channel, often called a swale. This will carry the water away as long as the swale has been properly graded to direct the water downhill.
Should your water problem be caused by circumstances beyond your control, such as underground springs, high water tables or creeks that have been piped underground, you might need to fix it by using subsurface pipes, sump pumps or both.
If you are unable to resolve your problem by following these steps, contact a professional, such as a civil engineer trained in hydrology, landscape architect or other landscape professional trained in diagnosing drainage issues.
Another tip is to check the composition of your soil. Storm water doesn’t always flow away from your property and might remain on-site a little longer. This could be because your property is boggy with poor soil percolation, or its composition allows too much water to filter directly into the ground.
You can see if you have poor soil percolation by digging a hole, filling it with water and seeing how long it takes to drain. The exact length of time depends upon the size of the hole, but you’ll know if you have poor drainage. Poor percolation occurs when water doesn’t drain quickly enough.
Most varieties of plants will not do well installed in hard, poorly drained soil. Improve drainage in this type of area by placing up to one-third compost into the native soil that is the problem area. Dig it in as deeply as 12 inches to improve the soil over as wide an area as possible.
Use a rototiller to break up the soil if the area is large or the soil too hard to dig with a shovel. If you don’t own one, you can rent one from an equipment rental company, such as Home Depot, or check with your local hardware store.
Joel M. Lerner is president of Environmental Design in Capitol View Park, Md. E-mail him at email@example.com.