# french drain - distance from foundation



## HHac8014 (Jan 1, 2010)

Started on a french drain today, and had a friend come by to give his thoughts on my progress. His first comment was that the trench seemed too far away from the house (It's about 1 and a half, or 2 feet from the wall/foundation. 

He had always done them flush with the foundation, and even brushed tar against the foundation to add an barrier. I see pictures of both on the internet...

I posted two that fit his idea - trench flush w/ footing. And two more like my three hours of work (a few feet back).

Would love forum views on pluses/minuses of each methodology..


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## Daniel Holzman (Mar 10, 2009)

This topic has been discussed repeatedly on this site, you can run a search and get dozens of hits. As to where you put the drain, it doesn't make much difference if it is next to the foundation or a few feet away. Far more important is that the invert of the drain be at least six inches lower than the maximum groundwater water level you are willing to tolerate. I have always specified that the drain invert be approximately one foot below the basement elevation, if that is not possible we relax the criterion a little bit. The construction of the drains you showed seems pretty good, I always use 4 inch perforated PVC pipe, holes down, wrapped in filter fabric, with crushed stone carried upward to grade, much like the pictures you showed. Others prefer to wrap the stone around the pipe in filter cloth. From my experience, either way works OK.


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## HHac8014 (Jan 1, 2010)

Thanks Daniel, I did see the hits and there's some good content in there. There was nothing on distance from foundation though. I just feel like it makes sense to take that water away before it gets anywhere near the house. Whereas drawing it in and against the foundation (with permeable stone right up against the foundation blocks) seems like letting the enemy (water) up to the gates and to the brink before the pipe has a shot of sweeping it away.


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## AllanJ (Nov 24, 2007)

If the pipe is right up against the foundation, the trench can be no deeper than the underside of the foundation footings. You can get the trench 4 to 6 inches deeper than the bottoms of the footings if the entire trench is 12 to 18 inches respectively out from the side of the footing.

More than 2 feet from the foundation and there may be a water table gradient rising as you get closer to the foundation, not good.

I suggest not wrapping the pipe directly with the filter cloth otherwise the water collection by the pipe is impaired where the cloth clings to the pipe.

You should not have basement flooding problems if the drain pipe is well below the basement floor surface.


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