How to Construct a French Drain

Drainage is the secret to a dry basement and a healthy yard. When water pools against your foundation or turns your lawn into a bog, you aren't just dealing with mud—you are inviting structural rot and soil erosion that will cost a fortune to fix later. A French drain acts as an underground highway for water, intercepting it before it reaches sensitive areas and carrying it to a safe discharge point. Doing this well requires more than just digging a hole; it demands precise grading and proper layering. You want to wrap your pipe in filter fabric to prevent silt from clogging the system, and use clean, crushed stone to encourage steady water flow. When finished, your yard should look undisturbed, but your moisture problems should vanish overnight.

  1. Map Your Water's Route. Outline your trench line using spray paint, ensuring a consistent downward slope of at least one inch for every eight feet of run. Start at the problem area and end at a low-lying discharge point, such as a storm drain or a dry well.
  2. Dig Deep and True. Dig a trench approximately 12 to 18 inches wide and at least 18 to 24 inches deep. Ensure the bottom of the trench follows the slope you marked out, checking with your level every few feet.
  3. Block Soil, Allow Flow. Lay non-woven landscape filter fabric along the bottom and sides of the trench, leaving enough slack to overlap the top later. This fabric is critical to stop soil from clogging the gravel and pipe.
  4. Create Water's Path. Pour 3 inches of clean, washed gravel into the bottom of the trench over the fabric. Rake it smooth so it maintains the consistent downward slope toward your outlet.
  5. Lay the Drainage Spine. Place your perforated PVC or corrugated pipe on the gravel base with the holes facing downward. Connect segments securely and ensure the entire run maintains a steady, continuous decline.
  6. Seal and Stabilize. Fill the remainder of the trench with gravel until it is about 4 inches from the surface. Fold the excess landscape fabric over the top of the gravel to fully encase the stone and pipe.
  7. Erase All Evidence. Top the remaining space with the original soil you removed, compacting it slightly to prevent a sunken trench line. Reseed the area with grass or replace your sod to hide the work completely.