In my last post I wrote about the war I’m waging against water penetration at my home in Milton, Mass. When you buy a home in this section of New England, you have to anticipate damp basements and wet weather. These two don’t go together well, and the water table is only coming up. If you want a dry, useful basement, you’re going to need to take a few steps to keep it that way. I outlined the first couple already, so now for step 3. Drum roll please…install a French drain!
Some of my readers may have never heard of a French drain…well I intend to enlighten you.
There is no hard and fast definition of a French drain
A French drain is essentially, a perimeter drain. Most frequently it resides on the interior of a property. So as to avoid carpal tunnel syndrome, I will plagiarize directly from Wikipedia:
A French drain, or weeping tile (also blind drain, rubble drain, rock drain, drain tile, perimeter drain, land drain, French ditch, sub-surface drain, sub-soil drain or agricultural drain) is a trench filled with gravel or rock or containing a perforated pipe that redirects surface water and groundwater away from an area. A French drain can have perforated hollow pipes along the bottom to quickly vent water that seeps down through the upper gravel or rock.
French drains are primarily used to prevent ground and surface water from penetrating or damaging building foundations. Alternatively, French drains may be used to distribute water, such as a septic drain field at the outlet of a typical septic tank sewage treatment system. French drains are also used behind retaining walls to relieve ground water pressure.
The earliest forms of French drains were simple ditches, pitched from a high area to a lower one and filled with gravel. These may have been invented in France but were described and popularized by Henry Flagg French (1813–1885) of Concord, Massachusetts, a lawyer and Assistant US Treasury Secretary, in his 1859 book Farm Drainage. French’s own drains were made of sections of ordinary roofing tile laid with a 1⁄8 in (0.32 cm) gap left in between the sections to admit water. Later, specialized drain tiles were designed with perforations. To prevent clogging, the gravel size varied from coarse at the center to fine at the outside and was designed based on the gradation of the soil surrounding the drain. The particle sizing was critical to keep the surrounding soil from washing into the voids in the gravel and clogging the drain. The development of geotextiles greatly simplified this procedure.
Ditches may be dug by hand or with a trencher. An inclination of 1 in 100 to 1 in 200 is typical. Lining the bottom of the ditch with clay or plastic pipe increases the volume of water that can flow through the drain.
Modern French drain systems can be made with perforated pipe (weeping tile) surrounded by sand or gravel and geotextile or landscaping textile. Landscaping textiles are used to prevent migration of the drainage material as well as preventing dirt and roots from entering and clogging the drainage pipe. The perforated pipe provides a minor underground storage volume but the prime purpose is for the perforations to drain the area along the full length of the pipe and to discharge any surplus water at its end. The direction of percolation will depend on the relative conditions inside and outside the pipe.
Subsurface drainage systems have been in common use for centuries.
They take many forms, but are all similar in design and function to the traditional French drain. There are scores of companies who sell perimeter drainage systems currently. Each suggests theirs is the best. I chose Basement Systems as I thought their proprietary design made a lot of sense. They utilize a drain pipe that sits a bit higher, has holes all along the pipe, periodic clean out ports and a pretty nice sump pump setup. Obviously the jury is out…but frankly, I hope the frontline drainage system I put in the yard renders this French drain useless.
It’s finally getting a bit wetter out, after an extremely dry fall in New England. I’ll update this post over the winter and the spring to let you know how the entire drainage system is working out. I intend to spray the basement with heavy duty white paint on the walls and battleship grey on the floor and make it a proper laundry, storage and work shop area.
If you have any questions about my experience installing drainage systems inside and outside of my home don’t hesitate to contact me.