Exterior French Drain System

What is an Exterior French Drain System?

The Exterior French Drain System collects and drains groundwater that pools around the footing of the exterior foundation. This system consists of connected perforated pipes along the exterior footing of the foundation and surrounded by gravel, which captures and redirects unwanted water to a particular area that is a good distance from the foundation.

Most homes today are built with some kind of an exterior French drain to naturally drain surface water or groundwater away from the foundation.  This system is designed to help eliminate hydrostatic pressure against the foundation wall and footing.  Over time, this system may clog or crush due to ground settlement or movement. Although this system is not bulletproof, there are ways to elongate the life of the system.  The professional installers at Sous-Sol Solution take the extra precautionary measures to ensure that your Exterior French Drain System will last longer.

Our Exterior French Drain System

• Excavate along the foundation wall down to the footing;
• Remove all existing weeping tile and stone, leaving a clean trench next to the foundation footing;
• Clean debris left on the foundation walls;
• Repair any foundation cracks and other crevices;
• Wrap foundation walls with Delta-MS Waterproofing Membrane;
• Install foam insulation board as a valuable add-on to the Delta-MS system (optional);
• Lay a bed of 3/4″ washed stone in the trench, next to the footing;
• Place 4″ perforated PVC pipes along the footing of the foundation, over the bed of stone;
• Extend cleanouts vertically from the PVC pipes to the ground level;
• Discharge pipes will be connected to a sump pump, drywell system, or to day light. Discharge method will depend on each circumstance.

Common Areas to Inspect Prior to Installing a New Drainage System

Grading: The ground level around your home must be sloped away from the foundation.

Gutters: Keep gutters clear from debris and leaves. Downspouts should be extended away from the foundation.

Window wells: Clogged or poor drainage in window wells will lead to leaks.

Driveways or Pathways: Must be sloped away from the foundation to eliminate surface water from draining down the foundation wall.

Common Causes for French Drain Failures

Improper Drainage:  Exterior French Drains count on gravity to drain properly.  When pipes are not installed correctly (e.g., pipes are not sloped correctly, pipes are too small, pipe extension is too close to the foundation) or if ground settlement has caused movement in the slope of the pipes, water can buildup and puddle in an area which can potentially cause hydrostatic pressure against the foundation.  Additionally, in some cases, Exterior French Drains are installed to run water within the trench area but nowhere to drain.

Clogged Draintile:  Over time, the dirt and sediment begin to clog the system.  The Exterior French Drain then fails to direct the water away from the foundation, causing hydrostatic pressure against the foundation and leading to cracked and leaking foundations.

Crushed Draintile:  As the ground settles over time, the pressure exceeds the strength of the draintile to the point that it crushes or breaks.  Once this happens, the Exterior French Drain loses its full potential to drain water away from the foundation.

How to Prolong Exterior French Drain Failures

Proper Drainage: Ensure pipes are properly connected and pitched towards the discharge pipe. Extend the discharge pipe a good distance from the foundation so that water is not draining back towards the foundation.

Clogged Draintile: Using a filter fabric sock can help prevent soil and other debris from clogging the draintile. Also, using a round 4″ PVC pipe is much better than the traditionally used, less expensive, black flexible corrugated plastic drain pipe.  Any dirt and debris entering the flexible corrugated drain pipes settles inside the corrugated grooves, leading to a build-up and a clogged draintile. When the pipe is not corrugated, any dirt or debris can be easily flushes away as the water flows through.  You will notice that all major underground pipes are round and not corrugated.

Crushed Draintile: Using a stronger and more durable pipe to withstand the pressure from the ground settlement. Instead of using the traditional black flexible pipe, we install 4″ perforated PVC pipes. Also, having a larger trench filled with 3/4″ washed stone around the pipes help in draining of the water and lessens the stress from ground settlement.