300.4[e]

[Bryan Price]

I know the 08 restricts conduit within 1 1/2" of the "nearest surface of the roof deck" to protect raceways from the deck screws.
We are doing a job that will have 4" of concrete between the roof material and the deck.
Any opinions?

 

[Flex]

Good question. You would think that they would have worded that better. Concrete should be an exception.

 

[resistance]

It doesn't need an exception for the OP's specific install.

I like what the FPN says: Roof decking material is often repaired or replaced after the initial raceway or cabling and roofing installation and may be penetrated by the screws or other mechanical devices designed to provide “hold down” strength of the waterproof membrane or roof insulating material. Exception: Rigid metal conduit and intermediate metal conduit shall not be required to comply with 300.4(E)

 

[chris kennedy]

Bryan, welcome to the Forum. IMO you have a 4" concrete slab, not a roof deck.

(E) Cables and Raceways Installed Under Roof Decking. A cable- or raceway-type wiring method, installed in exposed or concealed locations under metal-corrugated sheet roof decking, shall be installed and supported so the nearest outside surface of the cable or raceway is not less than 38 mm (11/2 in.) from the nearest surface of the roof decking.

 

[Bryan Price]

Bryan, welcome to the Forum. IMO you have a 4" concrete slab, not a roof deck.

Thanks for the welcome.
That is our "oppinion" we are being told "its a roof constructed with roof decking......."

 

[chris kennedy]

Any opinions?

One more thing, IMO I would (and have) Tapconed my EMT right to that ceiling.

 

[walkerj]

One more thing, IMO I would (and have) Tapconed my EMT right to that ceiling.

Me, too.:grin:

 

[resistance]

One more thing, IMO I would (and have) Tapconed my EMT right to that ceiling.

Never heard of the term "tapconed". What does this mean?

 

[cpal]

Never heard of the term "tapconed". What does this mean?

concrete screws

 

[resistance]

concrete screws

Thanks! Learned something new today!!

 

[chris kennedy]

Thanks for the welcome.
That is our "oppinion" we are being told "its a roof constructed with roof decking......."

Is the slab poured over 'metal-corrugated sheet roof decking'?

 

[Bryan Price]

Is the slab poured over 'metal-corrugated sheet roof decking'?

It will be, yes.

 

[Bryan Price]

We are going to support to the "deck" we are a bit worried though.
Its one of those jobs with more than one contractor, and MANY opinions.

 

[Smart $]

We are going to support to the "deck" we are a bit worried though.
Its one of those jobs with more than one contractor, and MANY opinions.

The only way to know for sure is to consult with the AHJ...

On the positive side, what you describe may not be metal roof deck. The construction is actually a composite metal deck, or a composite concrete slab with steel decking, or... and the list of names goes on because there is not any one standard name among the trades, mostly depending on which trade the construction is approached from, or the construction type name the architect decided to give it.

If there is some of this decking already in place, see if it has any embossing or ribbing which make it distinctly different than standard metal roof decking...

http://www.commercialsiding.com/metal-deck.php

 

[infinity]

What does the "nearest surface" mean?

(E) Cables and Raceways Installed Under Roof Decking. A cable- or raceway-type wiring method, installed in exposed or concealed locations under metal-corrugated sheet roof decking, shall be installed and supported so the nearest outside surface of the cable or raceway is not less than 38 mm (11/2 in.) from the nearest surface of the roof decking.

 

[Flex]

Bet it has to do with the up and down design of the decking. Seems to be saying the dont want the emt ran in the groove at all.

 

[infinity]

I'm guessing that looking up from underneath they're talking about the highest point on the up and down. Since a lot of this roof decking is only 1 1/2" deep you won't be running any EMT through the void above the bar joist.

 

[iwire]

I see it the other way, I would say they mean the point closest to the pipe or the 'low' rib.

I assume they know the roofers use screws long enough to reach beyond the low rib so we have to be 1.5" down from that.

The result is you will not ever be able to run 'in the ribs' you will always have to be below the ribs.

 

[Flex]

I see it the other way, I would say they mean the point closest to the pipe or the 'low' rib.

I assume they know the roofers use screws long enough to reach beyond the low rib so we have to be 1.5" down from that.

The result is you will not ever be able to run 'in the ribs' you will always have to be below the ribs.

Thats what I am getting at.

 

[infinity]

I see it the other way, I would say they mean the point closest to the pipe or the 'low' rib.

I assume they know the roofers use screws long enough to reach beyond the low rib so we have to be 1.5" down from that.

The result is you will not ever be able to run 'in the ribs' you will always have to be below the ribs.

So Bob, by your interpretation you cannot run EMT on the underside of the metal pan unless it were mounted on 1.5" or larger strut? My thought is that it's to prevent it from being run between the top of the bar joist and the metal pan unless you can maintain a 1.5" space.