Code Change Summary: Revisions to 300.6(E) broaden the protection requirements for wiring methods and materials installed under roof decking.

SME commentary: In the 2026 NEC^®, Section 300.6(E) has been expanded and revised to strengthen protection requirements for wiring methods located in or under roof decking. Previously, the rule in 300.4(E) applied only to cables, raceways, or boxes installed beneath metal-corrugated sheet roof decking. The updated provision relocates and broadens the requirement so that it now applies to all types of roof systems, not just metal corrugated decking. This change reflects the reality that wiring under any form of roof sheathing is susceptible to physical damage from nails, screws, and fasteners used during both original construction and re-roofing activities.

The revised language maintains the previous requirement for a minimum separation of 1½ inches from the lowest surface of the roof decking to the top of the wiring method. This spacing helps prevent accidental puncture when roof sheathing or roofing materials are attached with screw guns, nail guns, or other fastening tools. Wiring methods are also still prohibited from being installed in concealed locations within metal corrugated roof decking itself, which remains one of the more hazardous locations due to the nature of the roofing material having appealing voids that almost invite the electrician to slide in EMT for a fast and easy install when adding circuits below the roof line to an existing building.

Three exceptions accompany the revised rule. Exception No. 1 allows rigid metal conduit and intermediate metal conduit, with listed steel or malleable iron fittings and boxes, to be installed without maintaining the 1½ inch clearance. Exception No. 2 permits installation without spacing where the roof decking is protected with at least 2 inches of concrete cover. The 2026 edition adds Exception No. 3, which explicitly permits wiring methods and materials to be installed in concealed locations if encased in a minimum of 2 inches of concrete.

This broadening of coverage is particularly important because re-roofing is one of the most common renovation activities in residential, commercial, and industrial buildings. When old roofing is stripped and replaced, roofers may inadvertently drive fasteners through concealed electrical wiring beneath the decking. This hazard is not unique to metal roofs but applies equally to asphalt shingles, clay tiles, wood shakes, and other roofing systems where roof decking is replaced or repaired. Field experience has shown countless examples where wiring methods have been punctured by fasteners during roofing work, creating potential safety hazards.

By broadening the rule beyond corrugated metal decking, the NEC^® now provides uniform protection for wiring methods regardless of roof type. The consolidation of language into the broader term “wiring methods and materials” ensures that all applicable wiring systems, including cables, raceways, and conduit bodies, are addressed consistently. The alignment with Section 410.10(F), which provides similar protection for luminaires installed in or under roof decking, also improves usability and correlation within the Code.

Below is a preview of the NEC^®. See the actual NEC^® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2026 NEC^® edition of NFPA 70.

2023 Code Language:

300.4(E) Cables, Raceways, or Boxes Installed in or Under Metal-Corrugated Roof Decking. 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 inches 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.

Exception No. 1: Rigid metal conduit and intermediate metal conduit, with listed steel or malleable iron fittings and boxes, shall not be required to comply with 300.4(E).

Exception No. 2: The 1 ½ inch spacing is not required where metal-corrugated sheet roof decking is covered with a minimum thickness 2 inches concrete slab, measured from the top of the corrugated roofing.

2026 Code Language:

300.6(E) Wiring Methods and Materials in or Under Roof Decking. Wiring methods and materials installed under roof decking shall be installed to maintain not less than 1 ½ inch separation from the lowest surface of the roof decking. Wiring methods shall not be installed in concealed locations in metal-corrugated, sheet decking–type roofs.

Exception No. 1: Rigid metal conduit and intermediate metal conduit, with listed steel or malleable iron fittings and boxes, shall not be required to comply with 300.6(E).

Exception No. 2: The 1 ½ inch spacing shall not be required where metal-corrugated sheet roof decking is covered with a minimum thickness 2 inches concrete slab, measured from the top of the corrugated roofing.

Exception No. 3: Wiring methods and materials shall be permitted in concealed locations where encased in concrete not less than 2 inches thick. Boxes and conduit bodies shall be installed in accordance with 314.29.