Not kosher but it's what the architect/engineer wants

[jap]

If the Arch/Engineer are animate about having the conduit secured tight to the bottom of the roof deck, have them go up on a lift and drive a screw up through the roof.

If the screw happens to penetrate the bottom of a roofers boot working on the roof , and ,they don't get off the lift and out of town by the time the roofer gets down off the roof, the problem will fix itself.

The only thing that would resolve this issue quicker would be if there was a concrete contractor on the roof that this happened to.



JAP>

 

[woodduder]

We always called the raised portion of the corrugated deck the "flute". I worked on many walmart stores and we slid tens of thousands of feet of 3/4 conduit in the flutes of the decking.

In each flute we could fit 3 conduits. Those were my first years as a commercial electrician. We could run over a thousand feet of pipe per day.

When the 277 was turned on to the lights and to the RTU'S, we would have many tripping breakers.

The company I worked for was saving money not using Caddy bang on hangers, but we were wasting time repulling wire.

I would never run conduit in the flute today even if the code did allow it.

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[infinity]

We always called the raised portion of the corrugated deck the "flute". I worked on many walmart stores and we slid tens of thousands of feet of 3/4 conduit in the flutes of the decking.

In each flute we could fit 3 conduits. Those were my first years as a commercial electrician. We could run over a thousand feet of pipe per day.

When the 277 was turned on to the lights and to the RTU'S, we would have many tripping breakers.

The company I worked for was saving money not using Caddy bang on hangers, but we were wasting time repulling wire.

I would never run conduit in the flute today even if the code did allow it.

It was seemingly always done that way until the prohibition entered the NEC a few cycles ago. It was always an easy way to run EMT. Now you can run the EMT 1.5" below the underside of the roof decking but will have an issue where you need to cross over a steel beam. For that section you would need to take a short piece of IMC or RMC and make a 4-point saddle to cross between the top of the beam and the underside of the decking.

 

[mwm1752]

becauase of the corrugated design, it doesn't have a finished surface with an even plane, we need to keep most wiring methods 1.5 inches away from the lowest plane so any fasteners from above don't damage those wiring methods. RMC/IMC are about the only methods allowed to be directly mounted to it.

I agree with your statement but when installing a 6" concrete top you are no longer within 1.5" from the top exterior surface -- this type of construction generally has the deck welded to the I beams & fasteners are not used -- most core drilling is done during construction and placed in walls where conduits are vertical. The assembly of construction materials changes the design from corrugated roof decking to concrete structural roof decking. This design is not uncommon for floors which a tradesman can install the wiring method in the flute section above or below the corrugated metal.
so for example -- I have a structural roof deck as described and I want to run conduit on top of it to be buried in concrete for AHU's or any branch circuits need on the roof.

 

[kwired]

I agree with your statement but when installing a 6" concrete top you are no longer within 1.5" from the top exterior surface -- this type of construction generally has the deck welded to the I beams & fasteners are not used -- most core drilling is done during construction and placed in walls where conduits are vertical. The assembly of construction materials changes the design from corrugated roof decking to concrete structural roof decking. This design is not uncommon for floors which a tradesman can install the wiring method in the flute section above or below the corrugated metal.
so for example -- I have a structural roof deck as described and I want to run conduit on top of it to be buried in concrete for AHU's or any branch circuits need on the roof.

I tried to address this earlier. I don't have a problem if concrete gets poured over the metal decking, no fasteners for insulation attachment are going to be driven through the decking. NEC doesn't really make that distinction clear though, and it is the fasteners being driven through the decking that prompted the requirements. And I think I also mentioned that unless you did any fastening to that deck before the concrete is poured, you won't be doing it with quick and simple sheet metal type screws.