Over the next few weeks, thousands of Chicago area homeowners will look down into their basements and, much to their horror, see rising waters.
A basement can flood–or at least suffer from seepage–during a rainstorm as the ground around a home becomes saturated with rainwater.
“Water, as it attempts to flow underground, follows the path of least resistance, which can be along the exterior of a basement wall, which forms sort of a channel for the water to flow along,” says Mike Sanders, an environment team leader with the Prairie Crossings community in Grayslake. The subdivision was built without storm sewers, instead using natural drainage techniques to remove rainwater.
While flowing underground, rainwater can force its way through any small cracks in the basement walls and floors, or at the joint where the basement walls meet the floor.
One way to prevent basement flooding and seepage is to waterproof the exterior basement walls of your home. That requires an excavation and a coating of the walls, a fairly expensive process.
Another is to install a sump pump system, again another fairly expensive task for the typical homeowner.
A less expensive although fairly laborious method to waterproof your basement is through natural drainage techniques.
In a nutshell, this involves routing rainwater away from your house, preventing it from seeping in through basement walls. “The more you can keep the water away from your basement walls, the less likely it is that you will have water in your basement,” says Patrick Kelsey, a research soil scientist with the Morton Arboretum in Lisle.
Slopes and swales
Many basement seepage problems are the result of poor grading of the ground away from the house. “When a home is built, the ground is usually sloped away from the house,” says Kelsey. “But then over the years, the ground can settle and the slope can turn toward the house.”
As a result, instead of flowing away, water runs back toward the house and saturates the soil next to it.
Sidewalks, patios and driveways that lean toward the house can also aggravate the problem. “Standing water next to the house invites water problems in the basement,” says Sanders.
To remedy the situation, the grade of the ground needs to be changed so that it slopes away from the house. This may require a pickup bed or two of dirt that can be spread over the ground.
The grade should ideally slope about an inch or slightly more for every 10 feet of ground, says Kelsey. “While a downgrade, it will still look level by the naked eye,” he says. “To make sure you’ve got the right slope, use a string level, available at a hardware store.”
Sloping the ground will also require you to do a little landscaping.
“It’s not advisable to just dump the dirt over existing turf because that will create an underground channel in which water will still travel toward the house,” says Kelsey. “Instead, it’s best to remove the turf and then dump in the backfill. Then place the turf back over the new ground.”
Sloping sidewalks, patios and driveways, meanwhile, may have to be rebuilt or repitched to change the flow of water.
If you live on a fairly large lot, another way to divert water is to build a swale–a shallow trench that encircles three sides of the house in a sort of horseshoe pattern.
Dig the swale at least six feet from the house. Make sure that the ground between the house and the swale pitches toward the swale. Then fill the swale with gravel or crushed stones and cover it with dirt and turf.
Drain pipes
Another way to divert water from your home is through drain tile pipes. These perforated, ridged, black plastic tubes gather water during rainstorms and thanks to a downward pitch, carry the water away from the house.
“It’s how farmers deal with drainage all the time,” says Sanders. “It’s a good solution if changing the grade of the property is too complicated of a project.”
The first step in constructing a drain is to map out an underground channel where it will go. Ideally, as with a swale, the ground from the house will pitch toward the channel containing the drain tile pipe.
Take note of any sidewalks or driveways the pipe may have to cross under. In addition, where it discharges–preferably near a city storm sewer or a retention pond–is also highly important.
“You don’t want to just outlet it at the end of your property line and then make it your neighbor’s problem,” says Kelsey.
Once you’ve mapped out a plan, dig out a trench about a foot deep to support the drain tile pipe. Next, lay in about an inch or two of gravel. Then place the pipe in the trench, with the perforations facing down.
Cover the pipe with more gravel. Otherwise, the dirt can clog the holes. Finally, top the gravel off with a few inches of dirt and sod.
Gutter system
Another key to preventing basement seepage is making sure your home’s gutter system is in good shape and functioning properly. If the gutters are clogged, rainwater will pour over the sides, saturating the ground next to the foundation of the house. Clean gutters ensure the water is carried away from the house.
In addition, placement of the downspouts, the vertical pipes that carry the water from the gutters to the ground below, is critical.
“If the downspouts are just exhausting the water right next to the foundation, that’s just aggravating the situation,” says Kelsey.
Downspouts should exhaust as far away from the house as possible. This can be done with added pieces of downspout that run along the ground on a downward slop, or with downspout extensions that unroll when filled with water. The latter is especially good for downspouts that descend to a sidewalk.
A downspout can also be attached to an underground drain tile pipe to divert water away from the house. “The key is to keep the gutters screened so that the drain tile does not clog with debris such as leaves and twigs,” says Sanders.
Shrubs, flowers and turf
Selective landscaping will also help minimize basement seepage. Shrubs and flowers that are adjacent to the foundation walls can keep the ground damp through shading. The solution is to move shrubs and flowers at least four feet or so from the house. Then if the area adjacent to the house is properly graded, cover it with a grass or other thick ground cover.
You can also plant certain types of turfs and plants that aid in getting rainwater to quickly permeate deep down into the ground, rather than pooling against foundation walls.
For example, Sanders says natural prairie grasses, with their long roots, do a better job at water control than typical turfs, which descend into the dirt only about 3 or 4 inches. Prairie grasses with deep roots include Big Blue Stem, Little Blue Stem and Miscantus, an ornamental bunch grass.
The prairie grasses should particularly be planted in low-lying areas where water tends to pool during rains.
“This will require some careful thought to your landscaping, as you want these various elements to blend in together,” he says. “Certain prairie grasses can make your yard look like a field.”
You can also plant certain vegetation that “likes” water and will also aid the situation with their deep roots. These include both natural and exotic plants, such as irises, lilies, pickerelweed and a variety of sedges.
