# 3 or 4inch French drain



## joecaption (Nov 30, 2011)

#1, Foundations need to be water proofed and french drains installed outside.
Where did you hear that info?
Why address the issue after the water has already made it through the wall?


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## casio10 (Jun 26, 2016)

Cost of outside work and not really feasible. What info?


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## firehawkmph (Dec 12, 2009)

Pipe goes along side the footing, not on top of it. It sounds like you're running an inside drain. If you want to do it right, get 4" schedule 35 PVC pipe, perforated. Your concrete slab for the floor will sit on top of the footing. Pipe will not interfere with it. Should have gravel around the pipe too, which you should have a gravel base underneath the whole floor anyway. When I was building new homes, we ran inside and outside footer drains. They would get tied together with a sleeve through the footing. But we never used the black flexible pipe. Too flimsy and codes up here don't allow it for that purpose.
Mike Hawkins:smile:


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## casio10 (Jun 26, 2016)

Need to clarify original post. The pipe is not going on top of footing but next to it. The footing is approx 5 1/2 inches deep. The floor is only 2 inches thick. There is not enough room for the stone and 4inch pipe. Read several times do not dig below the footing. The 4 inch pipe will be above the floor, needing to have some type of curb to cover the pipe. Is a 3 inch pipe sufficient or will it not be able to handle the water? Thanks.


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## firehawkmph (Dec 12, 2009)

Depends. In my case, the inside drains were just a secondary precaution in case any water came up from under the slab. If you don't have a natural spring under your house and you have outside footer drains in place that are working, the 3" would probably be fine. Around here, there's a company that installs inside drainage by cutting out a foot of concrete along the inside of the walls and then installs 3" pipe that is in gravel and then flows into a sump crock. They also run a 4' tall piece of plastic sheeting that is about an 1/8" thick and set the bottom right into the trench they dug out. Then when they recement the area it gets embedded in the concrete and pinned to the wall. It catches any water that gets through the wall and forces it to flow down into the new drains.
Mike Hawkins:smile:


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## stadry (Jun 20, 2009)

this is like putting 5gal of wtr into 4gal buckets, no ? make your trench 1' wide & line it w/soil filter cloth,,, place the 3" pvc holes down & cover w/57 stone,,, fold filter cloth over completed work & lay down a length of 6mil plastic,,, THEN replace the conc 

IF measurements you posted are true, you'll still have a 2" thick floor,,, the conc will crack randomly so score contraction jnts every 2',,, be sure to install a cleanout @ the end opposite the run-to-daylight/crock end


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