French drain a reliable way to keep basement dry
Tim Carter
Q: Now that it’s spring, water is pouring into my basement. I’m tired of the intrusion as well as the mold that the water creates. I’ve done so much online research about how to stop the water that my head feels as if it’s stuffed with cotton. Have you ever solved issues of wet basements and crawl spaces?
A: Each spring, I receive hundreds of emails with similar questions. Some homeowners have water pouring or seeping into a basement or crawl space; others have a yard that resembles a swamp.
My college degree in geology has helped me solve tens of thousands of wetbasement problems. My primary focus in school was hydrogeology, the study of groundwater and how it moves.
The best way to solve leaking basements and crawl spaces or soggy soil is to install a linear French drain.
This simple trench drain in a yard intercepts the water moving sideways through the soil toward your home. A perforated pipe at the bottom of the narrow trench captures the water and redirects it to the lowest spot on your property.
The trench should be placed about 6 feet from your foundation and be on the high side of the land that’s sloping toward your home. The trench can be Lor U-shaped, as it protects The gravel bordering this building foundation is similar in size to that needed for a linear French drain.
your home. It depends on the direction of the overall slope of the land on your lot. Eventually, the trench ends on the low spot of your land, and the groundwater flows out of the pipe, only to re-enter the soil at a safe distance from your house.
In most cases, the trench
needs to be only 24 inches deep because most of the water movement through soil occurs in the top 12 inches, where there is plenty of air. I prefer the solid plastic pipe with two or three rows of holes drilled in it. The holes always must face downward, in the 4 o’clock and 7 o’clock positions.
Never put a sock on the pipe or filter fabric in the trench. Neither is required because silt doesn’t move through the soil; if it did, spring water would be muddy all the time.
The trench is filled with rounded or slightly angular gravel about the size of large grapes. Water moving through the soil encounters the gravel, falls down to the perforated pipe and uses the pipe to bypass your home.
I’ve created a free document at my website (http:// go.askthebuilder.com/ B1243) featuring a 3-D drawing of this trench drain as well as additional installation advice.