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