How deep should a French drain be?
French drain depth: About 8 inches to 2 feet deep should be sufficient for many water-diverting projects, though related systems, such as those built around foundations and sub-ground living spaces, as well as the bases of retaining walls, may be deeper.
How much soil should be in the top of a French drain?
Before installing any drain lines, coarse stone or gravel should always be put in the bottom of the trench to a depth of approximately two inches. Once the drain line is installed, coarse stone or gravel should then be put on top of the drain line leaving approximately 3–4 inches for topsoil for the lawn to grow in.
How much fall does a French drain need?
French drains need to have a slope of at least 1 percent, so the force of gravity will work for you. This means that the drain should slope down a total of at least one inch for every 10 feet of pipe.
Can a French drain be too deep?
Gas and water lines, electrical wires, and sewer pipes are some of the things that this digging may encounter. If the drain is dug below the footer, it will cause the home to settle and it’s important not to dig too deep.
How shallow can a French drain be?
Because there is a direct relationship between the diameter of a drain pipe and its relative effectiveness, make your trench no smaller than 12 inches wide, and aim for a depth between 18 and 24 inches.
What size gravel is best for French drain?
In general, you want to aim for ½ inch to 1-inch gravel for drainage. Areas that will see especially heavy flow may need larger gravel. Or, projects without drainage pipes may also need larger gravel. For example, a French drain without perforated pipe needs 1 ½ inch gravel.
What size rock is best for French drain?
1-1/2″
Use Natural 1-1/2″ round rock for best drainage. Washed rock is ideal. Avoid small pea gravel as the spaces in between stone is smaller minimizing flow rates. Avoid Crushed Rock (minus) that compacts and has “fines” that will clog pipe inlets.
How far should French drain be from foundation?
Recommended French Drain Installation Distance We recommend installing the french drains between 2 and 5 feet away from the foundation. There are a few variables that impact the exact distance to dig the new drain lines to carry water away from your home.