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Thread: Conduit supports on metal roofs

  1. #11
    Join Date
    Jun 2004
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    Cherry Valley NY, Seattle, WA
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    4,813
    Read carefully what it says in 352.44. An expansion coupling is only needed in select spots - only where you have two rigidly supported ends without 90's between them. Pretty much every other situaion you have enough flex in the system.




    Quote Originally Posted by Carultch View Post

    Does anyone else understand how this is supposed to work?
    No. Had a cable tray system on durablocks on a roof. IT had expansion joints in it. It was totally ridiculous and un-necessary.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  2. #12
    Join Date
    Nov 2015
    Location
    CA, USA
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    681
    Quote Originally Posted by electrofelon View Post
    Read carefully what it says in 352.44. An expansion coupling is only needed in select spots - only where you have two rigidly supported ends without 90's between them. Pretty much every other situaion you have enough flex in the system.


    No. Had a cable tray system on durablocks on a roof. IT had expansion joints in it. It was totally ridiculous and un-necessary.
    Floating blocks are great. Just make sure you put something between the block and the roof membrane to protect the membrane from abrasion. Also, don't float the blocks an inch above the roof hanging from the conduit, I've seen that many times.

    Unlike PVC, IMC is probably not going to buckle or pull apart, it's just going to rip the mounting off whatever it's screwed too if it moves too much.

  3. #13
    Join Date
    Jul 2007
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    Clark County, NV
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    Quote Originally Posted by pv_n00b View Post
    ...make sure you put something between the block and the roof membrane to protect the membrane from abrasion...
    What would be normal things to recommend for this? I'm starting to see more and more of these types of roofs, and it's only a matter of time before I'll be running conduit on one.

  4. #14
    Join Date
    Oct 2009
    Location
    Austin, TX, USA
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    10,159
    Quote Originally Posted by MAC702 View Post
    What would be normal things to recommend for this? I'm starting to see more and more of these types of roofs, and it's only a matter of time before I'll be running conduit on one.
    Most roofing companies that supply bitumen and TPO roof membranes require that slip sheets of the same type material as the roof membrane be placed under ballasted racking and conduit supports in order to preserve the roof warranty. A few even require that the slip sheets be exactly the same as the membrane (i.e., their product).

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