Installing French Drains for Yard Drainage

French Drain Landscaping IDEAS

Ideas / March 18, 2013

What are French drains? When are they useful? How do you install them?

If your neighbor's land stands at a higher elevation than yours, you may be experiencing problems with excessive moisture on your property. Water from your neighbor's property may be running down the slope (just one of the challenges of landscaping on a hill) and spilling onto your property. You need better yard drainage. One option in such cases is installing French drains.

When some people speak of a "French drain, " they refer to a trench in which a drain pipe is laid; the trench is then filled in with gravel. But the traditional French drain (which is the type that this article explains how to install) is basically just a trench filled with gravel (no pipe). Also note that the term "gravel" is used differently in different regions. In this tutorial, "gravel" refers to an aggregate of small stones.

How to Install a French Drain

  1. Determine a spot on your property where the excess water coming off the slope could be re-routed. Determining such a location may end up being a matter of choosing the lesser of two evils. If water is currently spilling out at your house foundation and excessive moisture threatens to damage it, obviously almost any other spot would be preferable. The ideal French drain leach field would be an out-of-the-way area with sandy soil, through which the water could percolate harmlessly.
  1. But be sure your attempt at yard drainage will not adversely impact anyone else's land. Otherwise, installing a French drain could land you a lawsuit. Check your city codes before digging. Another preliminary step that could save you headaches later is checking with your local utilities concerning the whereabouts of underground cables and the like, so that you will know where not to excavate. There is a quick way to check: just dial the Dig Safe phone number.
  1. Locate the best area for a French drain. Find an area along the slope on your side of the property line where excavation would be easiest (that is, free of obstructions). Trench lines should be plotted out before you begin digging French drains. You need to create your own mini-slope to carry the water down to its destination. A grade of 1% (that is, a drop of 1 foot for every 100 feet in length) is often recommended; others advise a drop of 6 inches for every 100 feet. Getting the water to go where you wish is essential for improving yard drainage; the grade will facilitate your efforts.
  2. So how do you measure the grading for a French drain? Pound two stakes into the ground to mark the beginning and end of the trench. Tie a string tightly to one of the stakes, then run it over to the other stake and tie it off there, too, but loosely (for now). Attach a string level to the string, adjusting the string to get it level. Once it is level, tighten the string at the second stake. Make sure the string is taut. Now begin digging the trench. As you dig, you will be able to measure down from the string to make sure that you are achieving the desired grade.
  3. Check yourself as you go. For instance, if the trench for the French drain is to be 100 feet long and the grade 1%, then by the time your trench is 50 feet long, it should be 6 inches deeper than where you began excavating.

Source: www.thespruce.com