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French drain directly under foundation

French drain directly under foundation

French drain directly under foundation

Can a house be built directly over a spring head? if permits(state, fedral) are obtained, can I do it? and if done are there any recommendations for methods to accomplish that? would a French drain system suffice? What are future complications and issues that i need to consider? Any help will be greatly appreciated.

RE: French drain directly under foundation


Can a house be built directly over a spring head?

Yes... but not with the approach you appear to have in mind. When a house is over water or even a wet area, don't want the living space coupled with the ground. The Owner will have ongoing moisture / mildew / mold issues no matter what steps are taken (e.g. vapor barrier, french drain, sometimes even forced ventilation of a closed crawl space).

Best to have natural ventilation between the living space and the ground:

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RE: French drain directly under foundation

Sorry BigH similar conditions exist all the time, as at my house with ground water table darn close to the basement. The key, if there is one, is to keep the resulting drained water table as low as possible. A geotech experienced in use of graded filters can come up with a solution, quite likely requiring a pump. Now that's where questions come in. Do you want to have a pump capable of working or available 24/7? Since the site is noted as having a spring, maybe there is a place down hill where it can drain to by gravity and no pump needed. This would be the same principle we use where water is found when a roadway cut encounters it. You drain it off to where it is out of the site needing protection. OK, if you are in a cold climate area, then in winter will that discharge area freeze up and no water gets there, leaving the house with a wet basement? It ain't easy solving this situation, but it can be done by using the right techniques. So start off and forget the words French Drain. Be careful, you don't want to undermine the house with erosion via this system.

RE: French drain directly under foundation

ANY gravity drain system will eventually get clogged with silt.

Is this a spot spring, or a line?

If the spring is artesian, can you catch the water low and pipe it laterally to a natural drainage course away from the structure?

Mike McCann, PE, SE (WA)

RE: French drain directly under foundation

Mike: I can show you some still working after 55 years. If done right they last forever. Those done for my Master's in '54 even older.

An edit here. I refer to the Wisconsin code for footing drains as developed by plumbers, not engineers, section SPS 321.17. There they spec a pea gravel with the percentage passing the #8 sieve as 0 to 5%. Any agency that specifies that as the drainage material around a performed drain or pipe wrapped with fabric darn well has lots of plugged drains. My efforts to change the Wisconsin code falls on deaf ears. Reason: only plumbers control what the code says.

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