Clearance Requirements Under Metal Roof Decking

A cable, raceway, or box installed under metal-corrugated sheet roof decking shall be supported so the top of the cable, raceway, or box is not less than _____ from the lowest surface of the roof decking to the top of the cable, raceway, or box.

a) ½ in.
b) 1 in.
c) 1 ½ in.
d) 2 in.

See answer and applicable Code reference

The correct answer is: c) 1 ½ in.

Article 300 covers general wiring requirements for wiring methods and materials for all installations. As per Sec. 300.4(E), "A cable, raceway, or box, installed in exposed or concealed locations under metal-corrugated sheet roof decking, shall be installed and supported so there is not less than 1 ½ in. measured from the lowest surface of the roof decking to the top of the cable, raceway, or box. A cable, raceway, or box shall not be installed in concealed locations in metal-corrugated, sheet decking-type roof."

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