(D) Cables and Raceways Parallel to Framing Members. In both exposed and concealed locations, where a cable- or raceway-type wiring method is installed parallel to framing members, such as joists, rafters, or studs, the cable or raceway shall be installed and supported so that the nearest outside surface of the cable or raceway is not less than 32 mm (11/4 in.) from the nearest edge of the framing member where nails or screws are likely to penetrate. Where this distance cannot be maintained, the cable or raceway shall be protected from penetration by nails or screws by a steel plate, sleeve, or equivalent at least 1.6 mm (1/16 in.) thick.Exception No. 1: Steel plates, sleeves, or the equivalent shall not be required to protect rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, or electrical metallic tubing.
The intent of 300.4(D) is to prevent mechanical damage to cables and raceways from nails and screws. The Code offers two means of protection. The first method is to fasten the cable or raceway so that it is 11/4 in. from the edge of the framing member, as illustrated in Exhibit 300.3. This requirement generally applies to exposed and concealed work. The second method permits the cable or raceway to be installed closer than 11/4 in. from the edge of the framing member if physical protection, such as a steel plate or a sleeve, is provided. (A steel plate is illustrated in Exhibit 300.2.) As stated in Exception No. 1, this requirement does not apply to rigid metal conduit, rigid nonmetallic conduit, intermediate metal conduit, or electrical metallic tubing wiring methods because these methods provide physical protection for the conductors.
Exception No. 2: For concealed work in finished buildings, or finished panels for prefabricated buildings where such supporting is impracticable, it shall be permissible to fish the cables between access points.