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Plumbing on edge of Foundation

Discussion in 'Residential Foundation Codes' started by Capo, Jul 28, 2020.

  1. Capo

    Capo Registered User

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    Hi All,

    I am building a new home in North Carolina on a slab foundation. Recently, we noticed that they put the 2nd story rough-ins coming out of the slab foundation (4 inch PVC drain + water lines) in the middle of the pantry instead of in the wall (plumber measured wrong I assume).

    The builder is going to have the rough-ins relocated to be in the wall but is currently proposing the wall that back-ups to the garage vs a side wall that is interior to the home. My question is two fold:

    1) Is there code or industry standards that mandate how far away plumbing rough-ins should be from the edge of the slab? If it is too close, won't that risk the concrete slab breaking/cracking due to a small piece of concrete between the PVC pipe and the edge of the slab?

    2) Is there a concern with pipes freezing? My garage will be insulated, but not heated. It doesn't get super cold here usually, but can get the teens or 20s from time to time.

    My thanks in advance for any information!
     
  2. cda

    cda Sawhorse

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    Welcome


    Not into plumbing, Were there Plans??? Did it show location of the pipes??

    Changes might have to be approved by the city,,, If they are involved????

    Can you say what state you are in

    Sounds like you need to spend a lot of time at the job site, or hire third party inspector to watch over
     
  3. Capo

    Capo Registered User

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    Thanks for the reply!

    The home is being built by a national builder in North Carolina. I do not have a copy of the plans but I believe they were supposed to be on an interior wall. We paid for an upgrade for a large pantry and if I had to guess, they measured wrong and put the rough-ins where the standard size pantry should have ended. Since it's an elongated pantry, it's now in the middle of the floor instead of in a wall.

    We do have an inspector for a pre-drywall and pre-close inspection and I have been going down multiple times a week to try to watch for these items (I caught this issues). The builder is saying they will fix it, but I just want to make sure they do it correctly. They want to move it to the back wall that borders the garage since it is the closest wall, but the 2 concerns I called out above have me questioning what he told me.

    Thanks for any help!
     
  4. cda

    cda Sawhorse

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    Start over and do it per plans?

    Sounds like you need a copy of the plans

    Is there occupy-able space above the garage?
     
  5. Ty J.

    Ty J. Sawhorse

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    To answer your original questions, piping should be a minimum of 2-inches from edge of slab to prevent spalling of the concrete edge/corner; however it may still happen.

    Piping run vertically in the garage/house separation wall is fine for two reasons: 1) waste drains and therefore has only a minimal potential to freeze within the pipe, and 2) pipe should be held closer to the interior house side of the wall, with the insulation placed behind it to keep the pipe on the warm side of the wall.
     
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  6. Paul Sweet

    Paul Sweet Sawhorse

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    It would be good to increase the wall with the piping to nominal 6" or thicker to allow space for insulation behind the pipes.
     
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  7. Capo

    Capo Registered User

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    Thank you for the info! If 2" is the minimum but there is still a chance it could impact the edge of the slab, what is the ideal distance?

    Also, is there a specific guide or industry guideline I could reference when I discuss with my builder?

    Thanks!
     
  8. Capo

    Capo Registered User

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    Apologies, can't seem to edit my post to fix a typo. The first "guide" I mention should read "is there a specific code or industry guideline I can reference."

    Thanks
     
  9. ADAguy

    ADAguy Registered User

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    Check with Concrete Institute for edge of lab penetrations minimum dimension.
     
  10. ADAguy

    ADAguy Registered User

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    [​IMG]

    See location of fixtures adjacent to walls above footings. Plumbing penetrations would be localized. Bigger in diameter than anchor bolts.
    Penetration vs slab edge dimension is of greater concern if on an exterior wall but if a crack is caused it yields an entry point for insects and others.
     
  11. my250r11

    my250r11 Sawhorse

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    If in an exterior or garage wall, here they would need to use pipe insulation for the water lines.
     
  12. ADAguy

    ADAguy Registered User

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    understood but his concern is with edge distance and possible cracking of the concrete.
    The dia of a 2" pipe is larger than an anchor bolt which if centered in a plate would be +/- 1-5/8" from the face of edge.
    The requestor's concern may not be an issue except as I mentioned above if the edge cracked it might allow a path for intrusion by ants and others. Searched Google for slab details but they don't show the penetration of a pipe at slab edges.
     
  13. rogerpa

    rogerpa Silver Member

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    While not exactly your situation - ACI-318 states
    "20.7.5 Specified concrete cover for pipe embedments with
    their fittings shall be at least 1-1/2 in. for concrete exposed to
    earth or weather, and at least 3/4 in. for concrete not exposed
    to weather, or not in contact with ground."
     
  14. ADAguy

    ADAguy Registered User

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    hmmm? interesting
     
  15. Capo

    Capo Registered User

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  16. Msradell

    Msradell Sawhorse

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    Please let us know the final outcome.
     

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