If your land is at the bottom of a hill or below your neighbor’s property, you may have a problem with drainage and ground moisture. It may be time to install a drainage system. If you are having water issues, installing a French drain can help solve those problems.
So what is a French drain? It’s typically thought of as an underground drainage system with a French drain tile, but is basically a drainage ditch with gravel. It is installed along areas of high ground moisture, with the lowest end of the drainage system funneling water away to a desired area.
Begin by selecting a suitable location below the problem area for drainage. This is a low spot, preferably with sand for proper percolation. If this isn’t possible, a catch basin may need to be built at the low end. A catch basin can be made by digging a hole into the ground as deep as possible and backfilling it with crushed gravel and sand, each layer alternating the other at least two feet thick. The deeper the catch basin, the more water it will absorb.
So long as the drainage area doesn’t impact other peoples land you can take the next step before digging. Always call ahead to the utility companies to check for underground utilities. Once you’re sure you’re clear and free from underground utilities, septic tanks, trees, plants and at least 50 feet away from any wells, you’re ready to begin digging.
Setting up a laser level is probably the easiest way to measure the angle for proper drainage, but it’s not the only method. A level string line between two stakes is also a great way to complete a French drain. You just have to measure down with a tape measure versus using a laser.
Dig your trench at least 12″ deep but the deeper you go, the more money it’s going to cost to backfill it with gravel. Keep your budget and your depth in sync. The same goes for the width. At least 6-8″ wide is the minimum, just keep in mind the more dirt you take out of the trench, the more money you have to throw into it.
Work the French drains depth down the hill a minimum of 5″ per one hundred feet of length. This provides at least a 5% grade. In some locations this may be very difficult and the grade can be adjusted as needed. Too much below or above grade can cause for improper drainage.
Once the French ditch has been dug, use a landscape fabric or trench fabric to line the bottom of the trench. Backfill the trench with gravel and pull up the sides of the landscape fabric to sort of wrap the gravel like a tube. Use a final layer of landscape fabric to cover the gravel and cover it with dirt. Just make sure the top of the fabric is covered with at least 4″ of dirt.