NEC says I need to secure 1" nonmetallic rigid conduit (Schedule 40 PVC to be precise) every 3 feet, which makes perfect sense when it is hanging between supports horizontally, across joists, or on a vertical surface.

However, I am looking to run a length of conduit over my porte cochere. The plan is to have it go up into one soffit, cross over attic space (inaccessible, no stairs or opening) feeding it in via the soffit, and come down out the other. Its about 14' across and there is no real way for me to get in there to attach straps. It would lay on 1/2" to 3/4" plywood which constitutes the ceiling of the porte cochere. Can I leave this long of a run without a strap? It is 'supported' by the flooring.

My only concern is its not protected - outside the fact that you would have to drill through the plywood to hit it. There is a run of romex to four recessed lights in this space as well.

If it has to be supported, can I use something like a rooftop pipe support and feed them in to the space?

Any advice or pointing to somewhere in the code that hits this would be very helpful.

  • What type of nonmetallic conduit are you using for this job? Jan 16 '16 at 18:53
  • Shed 40 PVC 1 inch
    – DMage
    Jan 16 '16 at 18:59

You might want to check with the inspector first, but I'm going to say they'll allow it. NEC allows PVC to be supported by passing through framing members, so I'm guessing they'd allow it to be supported where running over framing members (especially in inaccessible areas).

National Electrical Code 2014

Chapter 3 Wiring and Protection

Article 352 Rigid Polyvinyl Chloride Conduit: Type PVC

352.30 Securing and Supporting. PVC conduit shall be installed as a complete system as provided in 300.18 and shall be fastened so that movement from thermal expansion or contraction is permitted. PVC conduit shall be securely fastened and supported in accordance with 352.30(A) and (B).

(B) Supports. ...Horizontal runs of PVC conduit supported by openings through framing members at intervals not exceeding those in Table 352.30 and securely fastened within 900 mm (3 ft) of termination points shall be permitted.

  • Thanks, can do. I was also considering using 4x4 blocks and using a strap to secure the pvc. I can feed them in through the soffit so that the conduit is raised above the decking to provide some separation just in the event anyone for whatever reason tried drilling through it in the future. Using the 3 foot spacing rule I would need to feed in 3-4.
    – DMage
    Jan 16 '16 at 20:23
  • @DMage how would you attach the 4x4 blocking to the structure? Securing the conduit to movable objects, seems strange.
    – Tester101
    Jan 16 '16 at 20:26
  • Could drill up through the plywood ceiling if needed, but don't see it being much different from a roof support if left unattached. It would just raise the conduit off the plywood, and allow for any expansion/contraction.
    – DMage
    Jan 16 '16 at 20:35

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