In the spring, melting snow and April showers conspire against your yard, unleashing a deluge of water on to just-thawed ground. To add insult to injury, yards are often improperly graded, creating perfect puddle conditions. Soggy, uneven ground can spell doom for lawns and plants; saturated roots loose oxygen and plants suffocate. When the runoff is finished wreaking havoc outdoors, it often heads for your cellar next, running in through cracks or leaks in the foundation, where it can warp floorboards, rust appliances and turn finished rooms into mildewed messes. Fortunately, regrading or rerouting can correct most drainage problems.
To prevent water from leaking through your foundation, look to gutters for your first line of defense. While gutter-and-downspout systems protect your house from rainwater and snowmelt, they can also compound drainage problems by concentrating roof runoff at a house’s corners close to the foundation. To carry water away, attach a sloped leader to each gutter and guide water at least 10 feet from the foundation. Alternatively, downspouts can dump directly into an above- or underground catch basin. In that case, runoff should be carried through a solid drainpipe to a drywell, an in-ground perforated tank that collects water and lets it seep into the ground. In the past, drywells were 55-gallon oil drums with holes punched in them. From the start, these were doomed to fail as they rusted and collapsed. Today’s high-impact plastic drywells are easy to handle and work efficiently on small drainage problems. Larger pre-cast concrete drywells require machinery for their installation but will handle larger volumes of water.
Houses without gutters often have leakage problems caused by water splashing against the foundation. In this case, a collection system should be installed at the roof’s drip line. Dig a v-shaped trench, line it with thick plastic and lay in a perforated pipe, pitched toward a drywell or outlet pipe. Then cover the pipe with landscape to keep out dirt and fill trench with stone to allow water to leech through soil and into the pipe.
Regrading the ground closest to your foundation can also help. Clear away plantings and gently build up the soil to slope away from the foundation. The 10 feet of ground closest to the house should slope at least six inches downward to keep water from seeping into the basement or flooding foundation plantings. However, keep soil at least eight inches away from wood siding to protect against rot and insects.
To remedy your yard’s waterlogged low points, regrade at least one inch of slope for every five feet of turf. If regrading doesn’t work, you can build exterior perimeter drains to stop leakage. There are two types of drainage systems, surface and subsurface. Surface drainage works well for clay-based soils, while subsurface drainage is generally best suited to soils of high sand or silt content. Other factors to consider when choosing the most efficient drainage system for your yard include land configuration (natural slopes or low points) and the amount and pattern of rainfall.
The typical surface system, designed to remove water that collects on top of the soil, consists of swales – shallow open trenches – leading to one or more dry wells that empty into a deep runoff trench dug in the lowest corner of the yard. Open trenches are the most effective way to intercept excess water puddling on the ground’s surface and carry it off the landscape.
Subsurface drainage systems consist of several French drains that carry off water from poorly drained areas through collection pipes linked to a deep runoff trench dug in the lowest corner of the yard. Ideal places to put French drains are the bases of slopes, along retaining walls, or any other area where water tends to collect. French drains are constructed using pea gravel or crushed rock, woven landscape fabric and a perforated, corrugated drainage pipe. Dig a three-foot-deep trench to carry water away from the area to be drained. Make certain that your trench is well sloped so that water is encouraged to move through the drain to the desired destination. Line the trench with landscape fabric to prevent the infiltration of the surrounding soil and keep the gravel porous so that water flows through easily. Then install a 4-inch or 6-inch perforated drain line at the bottom of the trench, and backfill with 4-inches of gravel and cover with drainage-friendly topsoil. Your entire system of drainpipes should connect to a 6-inch solid collection pipe that goes all the way down to the runoff trench.
Regardless of whether a house is brand new or 100 years old, the yard is usually a result of how the builders left it, with low and high points occurring randomly throughout the landscape. The slope in your yard that causes a drainage problem can often contribute to the solution: each of these drainage systems depends on gravity, not pumps, to work. If a downward slope to a low-point can’t be found, drywells may be required. Builders and owners alike often avoid hiring a landscape contractor but, for severe or extensive drainage problems, it’s best to consult a professional before digging in.
