During a one-inch rain, 1,250 gallons of water fall on the roof of a 2,000-square-foot house. Without proper grading, gutters, and downspouts, some of this water flows into your basement. To waterproof your foundation you must first manage the source of the water. Rain and rain runoff is often the source of wet basements and foundation repairs. Collecting and controlling surface rain water also can save you money on watering landscape plantings and save you time when mowing or trimming your yard.
To prevent water from leaking through your basement, look to gutters as your first line of defense. While gutters with downspout systems protect your house from rainwater and snowmelt, they can also compound surface drainage problems by concentrating runoff near its foundation. This water must be moved at least 10’ away from the foundation to prevent wet basement or foundation repairs. Downspouts can be directed into a catch basin and or drain pipe system.
Water should be carried through a solid drainpipe to a drywell, daylight or to a pop up emitter. Years ago, drywells were old 55-gallon oil drums with holes punched in them. From the start, these were doomed to fail as they rusted and collapsed. Today's recycled plastic drywells are easy to handle and work efficiently on many drainage problems.
The same type of system should be used for sump pump outlets. A sump pump installation is never complete until the water is directed away from the foundation so that it will not have to be pumped out of your basement again. The sump pump discharge line should be drained to a 3” or 4” solid line, that is buried, and then either run to daylight or to a pop-up emitter. It is very important for this discharge line to empty to a larger pipe as soon as possible, so as to not create back pressure on the sump pump.
Making sure the ground closest to your foundation is graded away from the home is also very important. When regarding this area be sure to use a clayey soil instead of mulch or other loose material. Water wicks directly down through mulch opposed to running off away from your basement. Clear away sod and plantings, then 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 landscaping.
For problems with consistently wet areas, drywells and catch basins can also be used. Buried drywells give this collecting water a place to go and can even be used with a drain pipe system to move the water to dryer areas. While swales can also be used, often swales can be very unattractive or cause mowing issues.
Surface drainage is the single most important application of foundation waterproofing. Unless you have an underground spring or an unusually high water table, the surface drainage portion of your waterproofing system needs to control the greatest amount of water.
A French drain, drain tile or perimeter drain is depression covered with gravel that redirects surface and ground water away from a wet area. A French drain usually has drain pipes along the bottom to quickly move water that seeps down through the upper layer of gravel or rock. French drains are common drainage systems, primarily used to prevent ground and surface water from penetrating or damaging building foundations. The French drain technique may be used to distribute water, such as that which flows from behind retaining walls to relieve ground water pressure.