French drain is an ancient tehnique in which a ditch is excavated around a building which is then filled with gravel, as a means to redirect surface and ground water away from penetrating or damaging building foundations. To create a French drainage system we first excavate around the perimeter of the building all the way to the footing of the foundation. We then wash the foundation and inspect it for imperfections. Any and all imperfections and cracks are then filled with cement (Shockcrete). Once this product has cured, we then spray on a protective coating of Elastomeric membrane which creates an impenetrable rubber barrier. Again once this product has cured a dimpled plastic Membrane called Delta-MS fully seals the foundation. We then lay out Weeping tile (perforated plastic pipe) around the building, coated with a Geotextile (used to prevent migration of the drainage material as well as preventing dirt and roots from entering and clogging the drainage pipe) over it and then cover both with 2 feet of crushed gravel (3/4 inch). Finally, the gravel is covered with earth all the way to the previous ground level, and lastly it is covered with sod or grass. The most common cause of basement water is unmanaged rain runoff. Rainwater from the roof flows down through the soil and collects at the bottom of the original foundation excavation. While the weight of the saturated earth alone can break a wall, the situation worsens when the water freezes and exerts a lateral force that can cause cracks and buckling... Exterior draintiles around the perimeter of the foundation footing are the first line of defense against groundwater. The simplest retrofit solution is to install a sump pump that carries the water away from the house.