A French Drain System is a method used to eliminate freestanding water away from a building. French drains, simply well dug trenches filled with gravel, sand and sometimes a drainage pipe, are usually installed at or near low points along the perimeter of a building where standing water can accumulate, saturate the soil, and permeate the building material. The system should end at a point on the property that will not drain back towards the building. The low cost and relatively easy installation, plus the ability to hide the drainage trench with a cover of grass or turf, makes this system very popular.
Rain, snow runoff and condensation can result in damage to a foundation or slab. Even if accumulated amounts and freestanding water are not visable, many times water permeates underground, unseen. This can result in unpleasant odors, wetness, dampness, the buildup of bacteria and mold, plus the breakdown of the foundation or slab itself – all potentially dangerous to the building and owners.
There are four basic ways moisture can permeate foundations or slabs. Having any one of these scenarios should prompt consideration of a French Drain System.
High groundwater – Meaning that the ground water level rises to a high point and stays there due to high snow accumulation and melt off, large quantities of rain, lack of water absorption due to low amounts of vegetation in the area or lack of soil drying by the sun due to an overabundance of vegetation in the area. Even the soil content, if it has a high amount of clay, will retain the ground water, keeping the ground water level high. These conditions traditionally happen with new buildings where a lot of vegetation is cleared or in mountain areas.
Foundation Flaws & Leakage – Cracks in the foundation material, windows, grout and caulking will allow water seepage into the basement or slap material. Accumulation of water, rain, gutter or roof runoff or snowmelt will find these cracks if left untreated. If a foundation wall has had adequate water and damp proofed and windows are sealed tightly, plus water drains quickly through the soil there is little to be concerned about. However, even hairline cracks can cause problems, a constant watch and wary eye should be maintained for problems.
Broken Gutters/Water Retention/Irrigation Systems –underground sprinkler systems, collection of rainwater runoff, and roof gutters all add conveniences to the building and owner. However, should any of these systems fail or spring leaks, free standing water can accumulate and find it’s way into a foundations, basements and/or slabs. Constant watch and yearly upkeep on these systems must be maintained.
Condensation – inadequate ventilation or too-tightly sealed homes will allow the moisture in humid air to condense and run to the lowest point of a building – usually the basement or foundation. Condensation problems usually occur in humid areas where air conditioning is used year round, in vacation homes that are used infrequently and sealed tightly, in areas where humidifiers are necessary, or when weather conditions promote frequently peaks and valleys of temperature changes.
Though installation of a French Drain System can be easy where a new building is concerned, older sites can present problems such as sidewalks, tree roots or other underground utilities that will make the digging a chore. In addition, there is a bit of mathematical precision regarding the slope of the drainage and length of the trenches needed and required. For these reasons, consider hiring a site engineer or other professional for a complex, large or difficult system should any of the circumstances listed above require the installation of a French Drainage System
