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Q. Here in New England, we usually attach 1x3 strapping to the ceiling joists before installing drywall. At most jobs, I see the electricians stapling the Romex cable to the bottom of the joists, parallel to the 1x3 strapping, so the wiring is about 1/2 inch or less from the back of the drywall. Does this meet the NEC, or does the wiring need to be recessed farther from the drywall?

A.Master electrician Sean Kenney responds: During the 12 years I worked as a residential electrical contractor, I routinely stapled cable between the strapping. All of the inspectors I encountered in Massachusetts, New Hampshire, and Maine accepted the practice.

Unfortunately, though, the National Electrical Code (NEC) is not clear on this issue, and some local inspectors may interpret the NEC differently from the inspectors I encountered. NEC section 300-4 states, "Where subject to physical damage, conductors shall be adequately protected." In a perfect world, the NEC would address the issue of whether cables buried just under the surface of drywall are subject to physical damage. But we do not live in a perfect world.

NEC section 300-4(d) may apply, but only if your local inspector considers strapping to be a "framing member." That section states that "where a cableor raceway-type wiring method is installed parallel to framing members ... the cable or raceway shall be installed and supported so that the nearest outside surface of the cable or raceway is not less than 1 1/4 inch (31.8mm) from the nearest edge of the framing member where nails or screws are likely to penetrate." The intent of this section is to keep the cable away from the zone where drywall nails and screws can be expected. This section does not require the cable to be 1 1/4 inches back from the drywall — only 1 1/4 inches away from the strapping.

If an inspector feels that the use of strapping creates a series of "shallow grooves," then NEC section 300-4(e) may apply. That section states that "cable ... installed in a groove, to be covered by wallboard, siding, paneling, carpeting, or similar finish, shall be protected by 1/16 inch (1.59mm) thick steel plate, sleeve, or equivalent or by not less than 1 1/4 inch (31.8mm) free space for the full length of the groove in which the cable or raceway is installed." If this subsection applies, the question remains whether "free space" refers to the depth of the groove or the distance of the cable from the strapping.

In my opinion, the practice is safe and legal, provided you keep the cable at a minimum distance of 1 1/4 inches from the edge of the strapping. But since the NEC is somewhat unclear, you should discuss this issue with your local inspector.

Wiring Between Ceiling Strapping

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