the interior of the roof or floor to increase the effective delay time.
par. 188.8.131.52(1)(d) for additional information.
Metal Roofs and Floors
a) Representative existing construction.
roof construction consists of three types:
o Steel-plate decking
o Ribbed-steel decking
o Corrugated-metal decking
Typical metal floor construction consists of four types:
i) Steel-plate decking. Steel-plate decking
typically ranges from a minimum thickness of 1/4 inch (6 mm) to a maximum of
1 inch (25 mm).
ii) Ribbed-steel decking. This decking consists of
long, narrow sections with longitudinal ribs from 1-1/2 to 2 inches (38 to 50
mm) deep, spaced 6 inches (150 mm) center-to-center. Special long-span
roof-deck sections may also be used. Common gauges used are No. 22, 20, and
18 (0.8, 0.9, and 1.2 mm), while the deep long-span sections are of heavier
gauges, ranging from No. 18 to 12 (1.2 to 2.7 mm).
iii) Corrugated-metal decking. This decking is
typically made of aluminum, galvanized iron, or protected (rust-inhibited)
metal. Corrugated aluminum may be either corrugated sheets, curved
corrugated sheets, V-beam sheets, or concealed clip panels. The corrugated
sheets and curved corrugated sheets are typically 0.024 or 0.032 inch (0.6 or
0.8 mm) thick with 2.67-inch (68-mm) corrugations 7/8 inch (22 mm) deep. The
V-beam sheet has a 4-7/8-inch (120-mm) pitch with 1-3/4-inch (45-mm) deep
corrugations with top and bottom flats of 3/4 inch (19 mm). Thicknesses are
0.032, 0.040, or 0.050 inch (0.8, 1.0, or 1.3 mm). Concealed clip panels are
13.35 inches (340 mm) wide by 3 feet (900 mm) up to 39 feet (12 m) long with
thicknesses of 0.032, 0.040, or 0.050 inch (0.8, 1.0, or 1.3 mm).
Protected metal is available in corrugated sheets,
mansard sheets, or V-beam sheets. The corrugated sheets have 2.7-inch
(69-mm) corrugations 9/16 inch (14 mm) deep. Mansard sheets have 6 beads per
sheet. The V-beam sheet has a 5.4-inch (135-mm) pitch with 1-5/8-inch
(40-mm)-deep corrugations and contains five Vees per sheet. The thickness of
all protected metal sheeting ranges from 18 to 24 gauge (1.2 to 0.6 mm).