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O.T. Drainage question

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  • O.T. Drainage question

    I put a little shed on a cement slab. The ground is fairly level with the slab. I found out that
    during a heavy rain, water will flow under the barn door.

    So .. French drain pops into my head. I dig the ditch and realize that I don't really have anywhere
    for the water to go. It's already at the bottom of the yard and right next to the neighbors fence.

    That night it rained like hell, but the water in the ditch never came close to the level of the slab.
    meaning .. just the ditch prevents the flooding. So I figure I would just fill the ditch with stone
    hoping it would act like when it was empty.

    I had already bought the drain pipe, a 4" rigid pipe.

    Silly question I have is ... would putting the pipe in there anyways ... would that not help delay
    the fill up ?

    John Titor, when are you.

  • #2
    If nothing else, the pipe will provide a bigger void for the water to fill and will require less gravel to backfill the hole.

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    • #3
      from my experience just putting in pipe will no provide any assistance. Pipe will probably float out (raise) until it is on top of the ground, Better just fill in with stone (use larger stone than shown in photo and cap with what you show) Due to your location, freeze-thaw will not be an issue so that will help some

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      • #4
        Pipe won't do you much good you already have the situation improved, what I would do is increase the width of your stones and totally fill to the top with stone and then place those cement step pads on top, tons of surface area and yet not all "mushy" when you walk through or drag out stuff with wheels from shed...

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        • #5
          Pipe would provide more void space than stone, so more volume to collect rainwater before the trench overflows.

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          • #6
            It may be a trick of the camera but the ground to the right looks higher than the slab, with nothing to break up the slope the water would head in direction of the slab, creating a lower drainage area (like he did) just before the slab is a good way to go, adding pipe might buy you some time over just rock but will not increase the saturation area below, double width the trench and adding rock will both buy immediate time for flash flooding and also good saturation drainage for long hard rains...

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            • #7
              I have installed French drains two times. One was along the edge of a building where I worked. The fair sized roof sloped down to that side and the rain water poured off in sheets. Another section of roof emptied onto that roof adding even more water to the deluge. The bad part was it was the "front" of the building and they had added a garden along this entire wall that was built up about 18 to 24 inches. So, it was a dam that held the water behind it and against the wall. They wondered why it leaked into the offices, including the GM's.

              I dug a trench and filled it with loose gravel. I ran two drain field pipes in it, one for the first half and the second for the other half. Drain field pipe is drain pipe with holes drilled in it. In this case it was to allow the water to enter into the pipe. The end of those pipe runs was run under a walkway (another dam) into the parking lot where it discharged. They laughed. But when the first big rain storm came, the water poured out the pipes into the parking lot and the offices were bone dry. It has been over 25 years since that installation but I occasionally drive past that building and if it is raining, I drive into the parking lot. The system is still working well today. The water still pours out into the parking lot as fast as it falls behind that elevated garden.

              The second one was in front of my Florida home. The drainage was a supposed to be via a shallow ditch near the edge of the road that they called a swale. Over the years the owners had built up their lawns above street level so the water could not flow along that route. However my drive way, including a semicircle, was installed according to code and followed the outline of the past tense swale. So when it rained, the rest of my driveway, the street and parts of the lawn drained into these depressed areas of the driveway forming a couple of lakes that took days to completely dry up.

              I dug three trenches across the island formed by the semicircular drive and installed drains at each side at the low point, next to the driveway. Again I used drain field pipe in the trenches. Normal drain pipe and fittings were used leading from the drains to the trenches. I put crushed stone below and all around the drain field pipe. I probably had about 45 feet of it in all. When it was done, I never had more than a small puddle at the edge of my driveway even after a heavy rain.

              My point is, the drain field pipe (perforated pipe) is an essential element of a French drain unless you do not expect to conduct the water away. And, when properly done, they do work. They work very well. Yours looks a little small to me, but then, it is a small building so it may be enough. You can always add more later.
              Paul A.
              SE Texas

              Make it fit.
              You can't win and there IS a penalty for trying!

              Comment


              • #8
                You might consider jacking up the shed 4" or so and putting it on a few 4x PT timbers or railroad ties. You might then need to add a wood floor. Or maybe lay some 4x8x16 concrete blocks which would provide drainage and ventilation through the hollow cores.
                http://pauleschoen.com/pix/PM08_P76_P54.png
                Paul , P S Technology, Inc. and MrTibbs
                USA Maryland 21030

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                • #9
                  Originally posted by PStechPaul View Post
                  You might consider jacking up the shed 4" or so and putting it on a few 4x PT timbers or railroad ties. You might then need to add a wood floor. Or maybe lay some 4x8x16 concrete blocks which would provide drainage and ventilation through the hollow cores.
                  This is of course problem #1, the slab was poured too low, you should always have to step up at least a little into a building not shuffle in at ground level...

                  Comment


                  • #10
                    Ok .. no surprises.

                    I truly wish I would have put at least one layer of block down with the wall bottoms on the block.

                    Tell ya what I did do though, I bought a 100' roll of 1/4" thick 10" wide rubber. Wrapped it around
                    a treated 2x4 with another treated 2x4 on top of that and the whole thing bolted down to the cement.

                    Leaks like a sieve ... ahahah .. And I thought I was being so smart.

                    AK has a point that it wouldn't hurt to make the ditch wider

                    I think I will throw the pipe in there to add to the void, but I'm not sure about the size of stone to put in.

                    To exaggerate the problem for a solution, If I put two giant stones in a bucket and fill it with water, I think
                    it will accept less water than with many little stones. Just guessing here. My knee jerk says its wrong but
                    my brain thinks that right.
                    John Titor, when are you.

                    Comment


                    • #11
                      Originally posted by Mike Amick View Post

                      To exaggerate the problem for a solution, If I put two giant stones in a bucket and fill it with water, I think
                      it will accept less water than with many little stones. Just guessing here. My knee jerk says its wrong but
                      my brain thinks that right.

                      Go with the knee jerk ...

                      I like that Shed - that's how Kazinski got his start lol seriously though cool weathered wood patterns

                      Comment


                      • #12
                        Install a dry well, 4' wide x 4-5' deep, soil fabric on the walls and filled with .75" stone.
                        Run your french drain in, cover with more fabric and at least 12" of top soil.
                        Len

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                        • #13
                          QSIMDO has the answer.

                          The only issue you might run into is if either you have impermeable clay soil, or if the area you need to put the dry well in is so wet that water fills it normally.

                          If the soil is impermeable, the dry well won;t empty. If the area is wet, it probably will back up, but may then drain down to the normal level fairly quickly, unless the entire low level area fills up.
                          1601

                          Keep eye on ball.
                          Hashim Khan

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                          • #14
                            Is it just a small slab for the shed? You could have the slab jacked up as well.
                            Andy

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                            • #15
                              Imagine, having all of you in the kitchen at the same time, trying to cook one recipe. I hope there's a lot of wine.

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