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Thread: How far from shop slab to place channel drain

  1. #1
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    How far from shop slab to place channel drain

    I'M nearly ready to set my channel drain in concrete. I like the idea of setting a "soldier course" on both sides of it. Using a full size brick, that would place the drain edge close to 8" away from the slab. The drip line from the roof is ~6". Will this work ok or should I set it closer.....or does it matter? I have the patio laid out with the bricks running parallel to the length of the shed but with a "soldiers course" on each end. I placed the "s around the term to indicate that at the present time I do not plan to lay them on edge, although I may decide otherwise.
    The form is not yet secured . Nor have I added rebar.
    I tried to upload a pic but it would not upload.
    If my question seems petty, this is my first time working with concrete. You may be thinking " 68 years old and never worked with concrete", but it be so.

  2. #2
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    You say the drip line from the roof is ~6". This is not clear to me.

    Is there a gutter on the building? If there is any chance water will run off the slab and/or roof and getting under the drain it might freeze and lift/crack the concrete drain if you are in a cold climate. Around here a french drain is typically used along a building. If there is any doubt, maybe get someone with experience to take a look and advise.

  3. #3
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    How high above grade is your slab? I would backfill to get a 1/4" slope per foot (actually, I would do about an inch or more per foot, expecting it to settle some) and place it there. So if my slab was 6" above grade I would backfill on a slope maybe 4 ft out, place my trench, add a couple layers of 8mil plastic over the backfill and into the channel drain, cover with 2" smooth river rock. That is how I did my basement walls and it keeps all the water away, without the need for gutters (no channel, just dug down another 8" at the end of the backfill and made sure all drainage moved away from the house.
    Comments made here are my own and, according to my children, do not reflect the opinions of any other person... anywhere, anytime.

  4. #4
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    Red face

    It's an Amish built garage. Why, because I wanted the heavier built floor, joists 12" on center.
    This model comes with a 6" overhanging roof, so there a little less than 140 square feet of rain. Then the patio is about 400 sq. ft. This channel drain will have no other rainwater to move.

    What I was really wanting to learn was...will the drain (very light gray) sitting out that much be unattractive compared to, perhaps 2/3 of a brick in front of and 1/3 of a brick against the slab.
    I thought it would look better fully surrounding the 4" of concrete on either side of the drain that secures it.
    It will serve no other purpose than removing rainwater.

    Twice I tried to upload a pic with no success.

  5. #5
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    If you get snow or ice it needs to be located so the mounds of snow stay away from the shop walls. It may only take a few feet of snow on the roof to fall off and cave in the walls. How often do you have to clear the snow off the roof? How deep is your frostline or depth to permafrost?
    Depends on water law in your state. If you are in the west you are probably under Spanish water law and that will affect your ability to channel water on or off your property.
    Bill D.

  6. #6
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    I bagan with the idea of regrading the existing patio down 2.5"straight to the new structure. Then from the end against existing garage foundation, sloping another 2.5" along the entire 20' length of the slab where the drain has a bottom outlet that can be cut/and or punched out, a 90* elbow added to attach to 4" drainpipe, to the rear of the lot which does drop and drain naturally down a revenue.
    The soffits on the 2 sides of the home that butt up against the patiio have gutters and a downspout which, by the way, will not be directed toward the channel drain.

    So I now have a patio with a rear view only. Covered by the wall of the living room on one side, the back wall of the attached garage on another and my new shop forming the 3rd cover.

  7. #7
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    Twice I tried to upload a pic with no success.
    It is likely your file is too large. There should be a way to convert it to a jpg file, if it isn't already one, and then adjust its size with software on your computer.

    It might be helpful if you mentioned if you live in an area with heavy freezes and snow or if you live in an area without such weather. It can make a big difference in being able to give good information.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  8. #8
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    I've had no problems in the past uploading pics of similar size. The ice would not be able to move to the subsoil. When it melts it should run down the drain. Or am I missing somethibg?
    I live within 2 miles of the first I-80 exit in Illinois coming east from Iowa. I've seen 30 below here in the past.

    Yes, it get cold here. I think the frost line is around 30".


    Hey, it loaded that time.
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  9. #9
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    What does your building code say about surface drainage away from buildings? There is a reason for what it says. If you don't have a local code then consider checking what it says about building grade in the International Building Code, IBC.

    It looks like some sort of ledger running along side your foundation below the siding. If that is permanent then it will hold moisture or direct moisture to the siding. If you have roof eve of 6 inches and no roof gutters the roof runoff will splash off the hard surface you are placing next to the building and it will keep the lower edge of the building damp during rainy season if you have a rainy season.

    Generally it is a good idea to use rain gutters and get all runoff, including runoff from the roof, away from the building at least 5 or 10 feet depending on the circumstances and surfaces. Concrete foundations, if allowed to stay damp for extended times will soak through to the inside and make a mess unless they are waterproofed on the outside.

    I have a garage shop with the slab slightly above outside grade. The concrete foundation extends 6 inches above the slab. A month ago I removed a perforated drain that ran along my foundation. The roof drains were connected to it and the perforated drain was prone to plugging because it was not sloped to drain. First off,when I bought the house I smelled mildew and had to remove the sheetrock to clean that up. Then I kept everything inside the garage away from that wall so I could keep an eye on it and let it stay dry until I figured out what caused the mildew. During this 2 year period, white residue formed on the concrete inside the heated garage. I finally figured it out that the perforated drain the builder installed next to the unsealed foundation was keeping the concrete foundation damp during the rainy season and moisture vapor was migrating through to the inside of the concrete and causing the damage.

    My thought is that you may get away with what you are doing if you use rain gutters and downspouts to keep splash away from your structure and the surface next to the structure is sloped 5% away from the building to the gutter you are building. Make sure your gutter is sloped so it doesn't plug with debris to drain to somewhere appropriate. It looks quite long to be able to slope to drain without getting deep at the outlet end. You may need to use a drain pipe at intermediate locations. You can look up what slope to use on your gutter so it stays clear of sediment or you can just clean it regularly.

  10. #10
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    Here's how I want to build it.
    On both sides of the drain will be a width of 4" of concrete, and there will be concrete beneath the drain. I plan to make that concrete and drain a tiny bit below the level of the bricks. Then I want a full length brick set as in photo on both sides of the concrete securing the drain. The inner row of bricks I can angle down a bit in
    In the direction of the drain.
    The very highest the ground level will be on the drain side which will be 5" below the surface of the slab.
    That was needed to allow for a 2.5" slope from the far end of the patio so all water will drain toward the drain. Then along the front of the shed the drain will slope another 2.5" to the back end of the slab where the water will run through a 4" drainpipe angled down away from the drain.
    The remainder of the slab is high enough to set ground level at 6 inches below the top of the slab.
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  11. #11
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    I've been given some good advice here from members and I now understand why my plan would not work as intended.
    So, I will put a gutter and downspout along the front of the shop. I will also apply an appropriate sealant to the side of the slab against the shop to prevent water penetration. I will also run a bead of Silicon between the bricks surrounding the drain as well as between the bricks and slab and all seams between the sections of the channel drain

    Will the channel drain set in cement right where I have it handle the rainwater ok?
    Would it be better to move it farther away from the slab?
    Last edited by Bill Jobe; 09-16-2018 at 3:49 PM.

  12. #12
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    To clear up any posible misunderstanding, the structure was not built on nor attached to the slab. It is an Amish pre-built garage resting on four 4"x6" skids.
    The remaining 3 sides will not have runoff from the roof and are sloped sufficiently to remove rainwater quickly.
    The ground along the 3 sides is 6" below the top of the slab.
    The slab itself is 4" thick. The perimeter of the slab is 12" thick.
    Last edited by Bill Jobe; 09-16-2018 at 3:56 PM.

  13. #13
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    Bill, although I probably don't follow everything you are doing I think you understand that water against the structure is ok as long as it isn't puddling or constant and that moving it away from the structure is important. There are many ways to do this and fashion can be part of it but moisture can cause problems over time. It is nice to see aesthetics incorporated into site design.

  14. #14
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    Just pulled the forms and hoping for a quick answer.
    To save on concrete I chose to add a 2x4 inside of the form and down deep enough to take up space whIle stiffening up the slab.
    As you can see in this photo i've yet to pull it out yet.
    We get bad storms in about 10 minutes. Would you lay reba r down there and pour the 2 or 3 bags I have left, then pack the top with clay, or should I pack gravel in there or just all clay?

    Other than about a 4'x4' slab for a pond filter this is my first experience with concrete.
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  15. #15
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    Too late. I no sooner pressed "post" when the sky opened up. Scrambled to cover what I could but heavy rain enough to fill the gutter on the outside of the drain but I was able to get the gutter against the shed covered with no water filling it up. Had to use my "Grizzly" crate plywood that I was going to proudly display in the shop somewhere, but hopefully it will retain the text on the wood.

    Anyway, fill the gaps with concrete against what's already poured or just backfill with clay? Bricks will butt up against the slab on both sides.

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