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Thread: Running circuits along roof?

  1. #1
    DIY Senior Member Nate R's Avatar
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    Default Running circuits along roof?

    My main panel is in our back entrance to the house, a little 4X4' area that was added on to the original house. I will be rewiring just about everything.

    The easiest/best route to the 2nd floor (really a 1/2 story) is along the roof of the house. The rafters are only 4". (Really closer to 3 3/4." VERY old wood.) So, I need to maintain 1 1/4" depth from both sides, correct? One one side to keep drywall screws from penetrating, and on the other side to keep stray roofing nails from penetrating.

    I was thinking of running NM cable this way. 4-5 circuits.
    So can I fasten them to the side of the rafter itself smack in the middle of it? Or is this considered unsafe enough that I should consider this part of the run in BX or feed individual wires in conduit?

  2. #2
    DIY Senior Member Nate R's Avatar
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    Nothing? Is my question not clear enough, or is there something else I need to add?

    I just need to know if I should protect NM anymore under a roof than I would in a wall?

  3. #3
    Electrical Contractor jbfan74's Avatar
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    You do not have to drill them. Are you asking to lay the cables on top of the ceiling joist, or nail them along the roof?
    Yes I am A Pirate-Jimmy Buffett

  4. #4

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    I don't understand if this will be outside "under the roof" or inside run in an attic "under the roof"? I assume you are not running this "on top" of a roof...

  5. #5
    DIY Senior Member Nate R's Avatar
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    Pic below. I want to run wires (4 or 5 NM cables) along the blue lines, (along the roof boards, the underside of the roof deck) up to the 2nd floor ceiling.

    The area will be finished again on the interior, FWIW.

    Hopefully that makes some sense now!


  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    I'd staple them along the side of the 2x material as close to the middle of the thing as possible. Assuming you do end up with nails IN the structure, they wouldn't hit the wire, and if you miss, unless it was right at a staple, it would probably just push the wire out of the way.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  7. #7
    In the Trades Bob NH's Avatar
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    If you run PVC conduit you can run three #12 MultiWire Branch Circuits (MWBCs) which provides 6 circuits. It requires 6 hots, 3 neutrals, and a ground, in a 1/2" PVC conduit which doesn't require the 1 1/4" distance from the edge.

    You can terminate the circuits in a large box and branch from there with indivual circuits.

    You don't have to derate #12 or #14 with up to 9 current carrying conductors in the conduit. Only the hots count as current-carrying-conductors in MWBCs.

    You can run 1/2 or 3/4" Schedule 40 PVC conduit in drilled holes in rafters or studs if you keep the holes lined up.
    Last edited by Bob NH; 07-01-2008 at 05:43 AM. Reason: Clarification

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