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French Drains
A French drain is a trench covered with gravel or rock or containing a perforated pipe that redirects surface and groundwater away from an area. A French drain can have perforated hollow pipes along the bottom to quickly vent water that seeps down through the upper gravel or rock. French drains are primarily used to prevent ground and surface water from penetrating or damaging building foundations.
A trench is dug with the bottom sloping toward the outflow point or sump. Once the trench is complete, filter fabric or "geotechnical fabric" is placed in the bottom and extended up both sides. The soil drain is then installed on top of the fabric with the perforations downward, and drain gravel placed over it. The trench may be entirely filled with gravel or only part way. In either case, the filter fabric is overlapped on top of the gravel and held in place by more gravel -- which then forms part of the landscaping surface -- or by soil, plantings, walkways, or other materials. |