# French drain



## cbrace55 (Mar 13, 2019)

Any thoughts on an outside french drain system? Landscaper wants to dig down 18 inches on outside and lay pipe. He says this will rid basement of water from floor wall joint. looking for opinions.


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## SGrabs33 (Feb 13, 2017)

I know they often put them around the perimeter of houses for that purpose. I was looking @ them lately because my mom bought a new old house and it had some humidity and water intrusion issues. I have to imagine it will help if there is water seeping into your basement.


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## Ecks from Tex (Apr 26, 2018)

cbrace55 said:


> Any thoughts on an outside french drain system? Landscaper wants to dig down 18 inches on outside and lay pipe. He says this will rid basement of water from floor wall joint. looking for opinions.


putting perforated pipe in the ground is almost always an option of last resort.

you want to push water off your property at the surface first. if there is no feasible way to do that, then pipe. and if you can't pipe off the property, you take it to a perforated holding tank and let it disperse.


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## Delmarva Keith (May 12, 2018)

As @Ecks from Tex says, first line of defense is positive slope away from house for at least 10' from house. If water table is still too high, a french drain 18" in the ground likely won't do much. French drain needs to be at footer depth, along side the footer so water pressure at wall / footer junction is lower than pressure below that junction (i.e., low pressure inside the pipe below the junction) otherwise water always flows from high to low pressure and that low pressure will be your basement.

To get rid of the water, depending on slope of the land, you may have to trench under the footer to a sump pit and pump in the basement. Doing it right won't be cheap.

A cheaper alternative (again, if lot grading doesn't fix the issue) is an interior french drain in a trench dug alongside the interior of the footer, draining to a sump pit / pump. Water will travel through the wall / footer junction, across the top of the footer and under the section of floor over the footer to the drain. During installation, drill weep holes at the wall / footer junction to relieve pressure outside the wall. Install a layer of gravel over the top of the footer to the trench, cover with plastic sheeting to keep concrete out of the gravel, then replace the section of concrete for the floor between the trench and the wall.


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