The main feature of French drains is they are dug relatively shallow, 18 to 24 inches deep, versus footing drains which go deeper – see our page on that.

Shallow trenches are dug around the perimeter. Ideally, if we can lay them around three feet away from the foundation, we will. We place high quality filter fabric on the bottom of the trench and pin the fabric to the surface soil. This filter fabric is also called geotextile fabric. We add a layer of gravel onto the fabric. The perforated pipes are laid on top of the gravel.

The holes are in the lower half of the pipes. This allows water to flow best inside the pipes. The pipes are angled down and away so gravity forces the water away from your foundation to a desired discharge point.

A slope of one inch for every eight feet in length is generally recommended. Once we lay all the perforated pipe and cover with gravel we overlap the geotextile fabric on top of the gravel so that all four sides of the system are covered, providing the maximum surface area for soil filtration.