If the rampage of El Nino has dumped water in your yard, then you might need a French drain. Oui? Interestingly enough, the name didn’t come from the romantic country of France. It came from the farm land of Massachusetts by a man named Henry French. He promoted this idea in his book on Farm Drainage in 1859 to surface water. Since then, it’s been adapted for subsurface water as well.
What is a French drain?
A French drain is a trench dug deep enough to channel water away from the water-logged area. A trench is dug deep enough to channel the water and divert it away from the area. Next it is lined with landscape fabric and stapled to the earth to prevent silt and soil clogging the drain. Next a layer of gravel is filled at the base on which the perforated socked pipe is laid. The remaining gravel is filled to the top creating a permeable surface for water to drain towards. Water is accumulated, enters the perforated pipe and then is transported to a discharge point. Depending on the environment and needs a common trench will be dug some 2 feet deep and 18 inches across. The slope of the pipe should be 1 inch every 10 feet of horizontal run for water to flow sufficiently and gravity flow to be maintained. (Contact a professional to examine the area to be installed and specifics.)
When do I need a French drain?
Soggy spots in the yard—
French drains are used to divert water out of low permanent soggy spots in the yard where surface water doesn’t drain fast enough or ground is saturated. The trench is dug and funnels and reroutes stormwater into municipality storm drains or to a created backyard rain garden.
If high humidity is being experienced in the basement or water is accumulating on the basement floors, a French drain can be installed around the perimeter of the foundation. Sump pumps are often needed when there’s not enough slope away from the house. Hydrostatic pressure against the foundation of the basement can cause foundational cracks and thus leaking. Calling a professional to come in and evaluate the situation is recommended to protect the integrity of your foundation and home.
Behind retaining walls—
When installing a retaining wall, adding a French drain behind a retaining wall will exit the water so it doesn’t cause hydrostatic pressure on the wall. If not, water will build up behind the wall and undermine it.
French drains are an effective way to move water out of unwanted spaces. Excess moisture will undermine the foundation of your home, cause unusable areas in your property and create unsafe conditions. We highly recommend after installing the French drain to install drain guards at the point of discharge. These will keep rodents and debris from accumulating in your drainage system and continue the flow of water without obstructions. If you need a French drain installed call your local landscaper for a consultation.