How to Install a French Drain

Footing drains, or French drains, are installed at the base of foundations to direct water that migrates underground away from the structure. Footing drains are an essential component of proper foundation construction and are required in most parts of the country irrespective of standing water conditions. Footing drains protect the cement footing of a structure from damage caused by water and from freeze damage where underground water above the frost line freezes and heaves the cement foundation, damaging the concrete or cement block stem wall.

Preparation

1. Dig down alongside your existing foundation until the bottom of your ditch is at least even with, and preferably lower than, the base of the foundation.
2. Grade the ditch bottom to slope toward the lowest corner or common point of the house where you intend to lead the footing drain away from your structure.
3. Clean the outside of the basement wall or stem wall to prepare it for a water proof coating. You can pressure wash it or use a heavy brush and detergent water with a strong rinse.
4. After the masonry dries, coat the outside of the concrete or cement block basement or stem wall with a good quality water proof coating using a paint roller, spray gun, or large, wide brush.
5. Let the waterproof coating dry according to the manufacturer’s directions.

Installation

1. Install a 2” to 4” layer of good quality pea gravel or drain rock in the bottom of the ditch and grade it to match the grade of the ditch.
2. Lay in the 4” drain pipe. ADS perforated pipe is the common building material to use. Consult your local plumbing or building code to find out which materials are approved in your area.
3. Make certain the pipe is laid down straight and properly graded.
4. Backfill the ditch a little at a time, tamping the backfill material as you go.

Tips

Many localities allow you to stub your gutter downspouts into the footing drain. If this is the case where you live, simply install tees on their backs at every downspout location, stub the footing drainpipe above the finish grade and install a downspout adapter to accept the downspout.

If your locality does not permit downspouts to be attached to the footing drain you will have to install a second 4” pipe line to accept roof runoff. That pipeline can usually be installed in the same ditch as the footing drain. Be sure to consult local building codes in your area.