Code Quiz of Day

Clearance Requirements Under Metal Roof Decking

March 27, 2015

Article 300 covers general wiring requirements for wiring methods and materials for all installations.

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."

About the Author

Mike Holt

Mike Holt is the owner of Mike Holt Enterprises (www.MikeHolt.com), one of the largest electrical publishers in the United States. He earned a master's degree in the Business Administration Program (MBA) from the University of Miami. He earned his reputation as a National Electrical Code (NEC) expert by working his way up through the electrical trade. Formally a construction editor for two different trade publications, Mike started his career as an apprentice electrician and eventually became a master electrician, an electrical inspector, a contractor, and an educator. Mike has taught more than 1,000 classes on 30 different electrical-related subjects — ranging from alarm installations to exam preparation and voltage drop calculations. He continues to produce seminars, videos, books, and online training for the trade as well as contribute monthly Code content to EC&M magazine.