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French drain around foundation; exterior concrete block wall sealing

Posted by Bob C on July 3rd, 1999 10:33 PM


I would like to install a french drain around the exterior foundation of my house. The house has a full basement; the depth below ground level ranges from approx. 8' at the deep end to 4' at the least deep end. The foundation is constructed of concrete blocks, and is 41 years old. The basement is 1750 square feet, and has had 2" of water in it before (mid 1998). The water came in through the concrete blocks between 1" and 6" above the basement floor all the way around the walls after heavy rains for several days. Extending the downspouts to 8' away from the house has kept the basement bone dry for over a year, but I just don't feel comfortable finishing it off knowing that it could flood again. I dug down to the footer in one location and confirmed that a french drain was never installed when the house was built.

I am having difficulty locating information (detailed information) on exactly how to install the french drain properly (type of drainage material, where the holes are in this material, what direction they face (up or down), what diameter the material should be, what type of "gravel?" to use, how much gravel, what kind of landscaping fabric to use, how to wrap the gravel and drain pipe, where to locate everything in relation to the footer and foundation wall, pitch, etc...). I was told that the black "accordian" drainage pipe (commonly found at Home Depot) is illegal to use for this purpose at this depth. I've tried to go to the Better Homes and Garden page I've seen mentioned in a few articles, but am unable to do so as the document has been moved.

While the trench is open around the house, I'd also like to coat the walls with something to seal them from water. I haven't had water leaking into the basement above 6" off the floor, but while this trench is open would be a really great time to seal the walls. The best I can tell, the were covered with tar 41 years ago. I went to Home Depot but they don't sell anything to seal the exterior block wall.

If anyone could help, with sources of information on the french drain and products to coat the exterior foundation walls, I would greatly appreciate it. This is one of the larger jobs I have tackled myself, and I certainly don't want to ever do this again. A (hopefully) nicely landscaped yard and new grass are after this project; having to dig all that up because of a mistake this first go around gives me chills.

Thank you for any help you may have!

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