Save your basement with a French drain

Posted by Woodrow Aames ~ July 28, 2011

If your basement is wet, moldy and frequently flooded, it may not be due to a flaw in your foundation. Often the culprit is leaking basement walls that are saturated from rain run-off. It's a sadly common occurrence when outdoor landscaping or elevations are sloped to drain toward your exteriors. The long-term damage can be devastating. The problem is so easy to remedy, it might shock you. All you have to do is put in an inexpensive French drain!

Protecting your home may be more important this summer than performing routine seasonal maintenance, and you can complete a French drain in short order.

Let's start with a brief history of the French drain. There is nothing French about it. This exterior plumbing remedy was first proposed in Concord, Mass. by attorney and Assistant U.S. Treasury Secretary Henry French. French's 1859 book, Farm Drainage, introduced the idea of drain fields, drainage remedies and filtration systems. You can learn more about it at Concord Magazine.

Installing a French drain

If you have serious woes with lawn drainage, berms, dry wells and French drains can spare you the misery of repairing foundations or exterior walls. Putting in a French drain is a perfect outdoor home improvement project for this time of the year. (Quick note: check with your municipality to see if there are permits, drainage laws or environmental provisions required for the project.)

Step 1. Dig a trench. You can dig the trench by hand or use a machine. The trench should extend to at least a width of two feet. The depth is up to you, but should be at least two feet for a slab foundation or six feet deep for a home with a basement. This is a gravity flow system. The slope of 1/8"-per-foot is a minimum incline. The trench must slope away from your home, with the top end where it meets the exterior wall at the highest point.

Step 2. Lay perforated pipe.

Choose your pipe. Rigid perforated PVC pipe can be simply unclogged by Roto-Rooter. Flexible perforated drain pipe can clog and is best left to farmers or irrigation experts who usually rip open trenches and cut new pipe. Try 4" rigid pipe that comes with drainage holes along the bottom edge.

Step 3. Cover the pipe.

Cover the length of pipe with a 12-inch minimum of washed gravel. Then lay filter fabric (from home improvement stores) over the gravel to block soil from sifting down into the pipe and perforations.

Step 4. Backfill

Use the topsoil you removed from the trenching to cover the pipe. Match fresh seed or turf with your existing lawn.

Want visual help? Watch the HGTV Pro video on French drains on You Tube.

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