Notes to ASM Standard

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(Notes are explanatory and non-binding, each provided to support the requirements, guiding principles and recommendations of the Standard.)

Notes to Part 1

Notes to Part 2

A-2.7 (Electrical Cables and Boxes)

Electrical boxes, fixtures, and electrical wiring (exposed or protected inside conduit) installed inside, on top of, or beneath a roof assembly may present hazards for roofing workers and building occupants, and may interfere with the roof design.

Many Tested Assemblies (roof assemblies tested under controlled conditions) rely on mechanical fasteners to secure some or all materials. Roof fasteners (which are self-drilling so they can penetrate steel decking) are capable of penetrating even the most rigid electrical conduit. When roofing screws contact an energized electrical system, workers can be shocked, sometimes with lethal consequences. Furthermore, electrical conductors damaged by roofing screws may not trip fault protection devices which generally do not respond to high-resistance faults. High-resistance electrical faults have been linked to numerous structural fires, which sometimes occur years after conductors were damaged. For these reasons, separating the electrical service from the roof assembly is critical.

Electrical conductor damage is not a problem exclusive to new construction. As roofs wear out and require partial or full replacement, mechanical fastening is often the only way by which new roof materials can be secured to the structural roof deck, to comply with the Building Code. When electrical systems are hidden by existing roof system materials, the design and construction of a replacement roof may be exceedingly difficult to execute.

Rule 12-022 of the 2021 Canadian Electrical Code, Part I, now prohibits the installation of “cables or raceways” within a roof assembly. Rule 12-022 is reprinted below (the term “roof decking system” used in the Rule has the same meaning as roof assembly used by ASTM International (ASTM D6630-08 Standard Guide for Low slope Insulated Roof membrane Assembly Performance), and as used in this Standard):

12-022 Cables or raceways installed in roof decking systems

1) Cables or raceways installed in accordance with this Section shall not be installed in locations concealed within a roof decking system, where the roof systems utilises screws or other metal penetrating fasteners.

2) Notwithstanding Subrule 1) the following circuits shall be permitted for installations in locations concealed within a roof decking system:

a) Class 2 circuits in which the open-circuit voltage does not exceed 30 V; and

b) embedded trace heat.

3) Where wiring is concealed within the roof deck system in accordance with Subrule 2), a warning label shall be installed

a) at all permanently installed roof access points where provided; and

b) in a conspicuous location in the roof area where the cabling is installed.

While this is a national code requirement directly resulting from a years-long endeavor by the RCABC, provincial adoption of the Canadian Electrical Code, Part I may be delayed because of the British Columbia code cycle. Nevertheless, the Design Authority is advised to adopt the requirements and prohibitions of the national Code, and to also adopt the following requirements for new construction or replacement roofing, as they apply.

Notes to Part 3

Notes to Part 4

Notes to Part 5

Notes to Part 6

Notes to Part 7

Notes to Part 8

Notes to Part 9

Notes to Part 10

Notes to Part 11

Notes to Part 12

Notes to Part 13

Notes to Part 14

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