Do you have water under your house?

If you have problem with water in the craw space of your foundation, or you have water infiltration through the bottom of your slab foundation, then a French drain is the most likely solution.

The most likely cause of the water penetration is through sub-surface water movement (Water Moving Below Ground). Barring the existence of a natural spring, this generally happens when surface water ponds or stands on the ground surface with no place to go. It will then "Soak In" and begin to travel below ground. The interesting thing is that through capillary action this water moving below ground can defy gravity and flow up to the surface. For many an unfortunate homeowner this happens under their per and beam foundation or in their sunken living room and even under their wood floors. If your house is on a pier and beam foundation and you have this musty oder that you just can't get rid of, water in the crawl space could be causing mildew and rotting under the house. Are your wood floors warping and becoming unlevel and unsightly, could be moisture from below.



French Drain Illustration

 If the water can't be caught at the surface before it travels below ground (which is often impractical), then the best solution is probably a French drain, sometimes called a curtain drain, which will create a barrier that will catch this subsurface water before it moves under the house. It is imperative that the bottom of the French drain system, where the perforated pipe is located, is below the footer or grade beam of the foundation. Preferably at least 6" below. It is necessary to maintain slope on the bottom of the French drain toward the discharge point. The drain may start out at 2.5 ft. deep, but by the time it gets to the end of the foundation it may be 3.5' deep. Many times a sump pump and pit will be necessary as a result of the required depth of the drain pipe.

 

Typical French Drain Plan

Hopefully the Illustration will help in understanding how the system works. Note that the shallowest point is at the upper right corner and the French drain is sloped so that the water will through the perforated pipe to the sump pit, where it is pumped uphill, out to the street.

There are many more applications for French drains, and there more components that can be added to the French system for those different applications, but for now, this is a simple system that can solve a terrible problem. I have seen many flooded crawl spaces and wet sunken living rooms that have been completely dried out with this system.