Understanding
the UL Fire Resistance Directories
Gypsum
Board: Gypsum panels with beveled,
square or tapered edges. For single layer systems
gypsum panels applied vertically with joints centered over studs. For single
layer systems (constructed with 1/2 in. thick board) gypsum panels applied
vertically or horizontally with vertical joints centered over studs. For two layer
systems gypsum panels to be applied vertically with joints centered over studs
and staggered one stud cavity on opposite sides of studs. Outer layer of
gypsum panels may be applied vertically or horizontally for systems
constructed with 1/2 in. thick board. Vertical joints in adjacent layers
staggered one stud cavity. For three and four layer systems inner layers to be
applied vertically with joints centered over studs and staggered one stud
cavity on opposite sides of studs. Vertical joints in adjacent layers
staggered one stud cavity. Outer layer may be applied vertically or
horizontally. The thickness and number of layers for the 1 hr, 2 hr, 3 hr and
4 hr ratings are as follows:
4