3.1.2
Metal Roofs
Wood-Frame, Wall-Bearing Masonry or Tile Structure with Metallic Roof and
Nonmetallic Exterior Walls, or Reinforced Concrete Building with Metallic
Roof: Metal roofs which are in the form of sections insulated from each
other shall be made electrically continuous by bonding. Air terminals
shall be connected to, and made electrically continuous with, the metal
roof as well as the roof conductors and down conductors. Ridge cables and
roof conductors shall be bonded to the roof at the upper and lower edges of
the roof and at intervals not to exceed 30 meters 100 feet. The down
conductors shall be bonded to roof conductors and to the lower edge of the
metal roof. Where the metal of the roof is in small sections, the air
terminals and down conductors shall have connections made to at least four
of the sections. All connections shall have electrical continuity and have
a surface contact of at least 1935 square mm 3 square inches.
3.1.3
Metal Roofs With Metal Walls
Wood-Frame Building With Metal Roof and Metal Exterior Walls: The metal
roof and the metal walls shall be bonded and made electrically continuous
and considered as one unit. The air terminals shall be connected to and
made electrically continuous with the metal roof as well as the roof and
down conductors. All connections shall have electrical continuity and have
a surface contact of at least 1935 square mm 3 square inches.
3.1.4
Steel Frame Building
The steel framework shall be made electrically continuous. Electrical
continuity may be provided by bolting, riveting, or welding steel frame,
unless a specific method is noted on the drawings. The air terminals shall
be connected to the structural steel framework at the ridge. Short runs of
conductors shall be used as necessary to join air terminals to the metal
framework so that proper placing of air terminals is maintained. Separate
down conductors from air terminals to ground connections are not required.
Where a grounded metal pipe water system enters the building, the
structural steel framework and the water system shall be connected at the
point of entrance by a ground connector. Connections to pipes shall be by
means of ground clamps with lugs. Connections to structural framework
shall be by means of nut and bolt or welding. All connections between
columns and ground connections shall be made at the bottom of the steel
columns. Ground connections to grounding electrons or counterpoise shall
be run from not less than one-half of all the columns distributed equally
around the perimeter of the structure at intervals averaging not more than
18 meters 60 feet.
3.1.5
Ramps
Lightning protection for covered ramps (connecting passageways) shall
conform to the requirements for lightning protection systems for buildings
of similar construction. A down conductor and a driven ground shall be
placed at one of the corners where the ramp connects to each building or
structure. This down conductor and driven ground shall be connected to the
counterpoise or nearest ground connection of the building or structure.
Where buildings or structures and connecting ramps are clad with metal, the
metal of the buildings or structures and metal of the ramp shall be
connected to ensure electrical continuity, in order to avoid the
possibility of a flash-over or spark due to a difference in potential.
SECTION 13100A
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