Corrugated roofing nec 300.4 E

Jpflex

Jpflex

Electrician big leagues
Location
Victorville
Occupation
Electrician commercial and residential
Nec 300.4 E

A cable, raceway, or BOX, INSTALLED in exposed or CONCEALED LOCATIONS under METAL CORREGATED sheet roif decking SHALL BE INSTALLED so that there is not less than 1/1/2 in measured from the lowest surface of the roof decking to the top of the cable, raceway or box


Then to contradict this, the nec immediately says, a cable, raceway or BOX shall NOT be INSTALLED in concealed locations in metal corrugated sheet decking.

this is the stupid ambiguous crap in NEC
 
Where does it say a raceway or cable cannot be installed in a concealed location ??
 
Jpflex said:
Nec 300.4 E

A cable, raceway, or BOX, INSTALLED in exposed or CONCEALED LOCATIONS under METAL CORREGATED sheet roif decking SHALL BE INSTALLED so that there is not less than 1/1/2 in measured from the lowest surface of the roof decking to the top of the cable, raceway or box


Then to contradict this, the nec immediately says, a cable, raceway or BOX shall NOT be INSTALLED in concealed locations in metal corrugated sheet decking.

this is the stupid ambiguous crap in NEC
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The context of the words "shall be installed" does not mean you are required to put a box under a metal corrugated roof.
 
They are fixing it for the 2026. The current language is contradictory with itself.
(E) Wiring Methods and Materials Beneath in or Under Roof Decking.
If subject to physical damage, wiring Wiring methods and materials installed in exposed or concealed locations under roof decking, shall be installed to maintain not less than 38 mm (11⁄2 in.) separation from the lowest surface of the roof decking. Wiring methods shall not be installed in concealed locations in metal-corrugated, sheet decking–type roofs.
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I wouldn't understand where you could conceal a wiring method in such a roof if, years ago when I was an apprentice, I had not been involved with stapling MC to the flat plywood roof sheathing before the hard foam panels and rubber membrane for lighting in an open ceiling dining room in a Chillis restaurant.

Someone might consider placing the wire or pipe on the corrogated metal before ...
 
farmantenna said:
I wouldn't understand where you could conceal a wiring method in such a roof if, years ago when I was an apprentice, I had not been involved with stapling MC to the flat plywood roof sheathing before the hard foam panels and rubber membrane for lighting in an open ceiling dining room in a Chillis restaurant.

Someone might consider placing the wire or pipe on the corrogated metal before ...
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I did a project with a finished wood plank ceiling and no space above it. The plans specified deep octagon masonry boxes extended through the corrugated metal deck, to be flush with the wood below, and rigid conduit above connecting the boxes. The the layers of insulation were installed and covered with the rubber roof membrane.
 
don_resqcapt19 said:
I did a project with a finished wood plank ceiling and no space above it. The plans specified deep octagon masonry boxes extended through the corrugated metal deck, to be flush with the wood below, and rigid conduit above connecting the boxes. The the layers of insulation were installed and covered with the rubber roof membrane.
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That would work better than MC because it's more difficult for the screws to go through unlike what my job experienced.
 
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