In search of any reference to installing residential pv system and fastening metallic conduit to and distance required from underside of wooden roof sheathing.
The NEC has no requirements for roofs with wooden roof decking, but I personally would follow the same provisions for metal roof decking in 300.4(E).
Interesting question. I agree with Bryan. But I don't know how you would do that. Are you intending to use a screw? Wood sheathing is only 1/2", OSB 5/8", how can you be sure that you will not penetrate the roof or roofing system? Are you using "really short" screws? Will this provide adequate support?
I after thinking about this issue, I actually submitted a public input to include plywood decking in 300.4(E). I hope you do as well.
I'm still debating it. My thoughts at the moment are:
You said, "plywood decking?" No OSB?
Let's take the case of 1/2-inch ply roof deck. What would you use to secure the standoff or whatever to the underside of the roof deck, a 3/8-inch screw? Will this provide support? How would we know they didn't use a 5/8-inch screw, and now they have penetrated the roof? I'm thinking that we may be opening up a pandora's box. Roofing has issues and the net result of the change (tho' unintended) may be damage to roofs.
I'm also thinking that they shouldn't fasten to the roof decking but they can simply fasten to rafters only.
I'm not certain on the material, i wasn't there personally!
Typically I see one hole straps to fasten conduits to underside of roof trusses or braces.
But let's just say you wanted to use a standoff strap (not sure what you call them these days) to the underside of roof plywood that is 1/2-inch.
How would you attach it? Will it hold? What about OSB?
don't think anyone would buy that!
Thanks Guys, a coworker was inspecting a residential installation and had me try to help him find something in the NEC but could only find the metal decking!
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