Understanding the UL Fire Resistance Directories - Ron Blank ...

Page 10 – Wall and Partition AssembliesUnderstanding UL• Additional layers of gypsum board are permitted to be added to any design.• Orientation, vertical or horizontal, of the application of gypsum board inwalls and partitions is specified in the individual design.• Except when gypsum board is allowed to be applied horizontally in the individualwall designs, horizontal butt joints of vertically applied gypsum board should bebacked by the same type studs as specified in the design. Alternatively,minimum i 25 gauge steel framing with a minimum i attachment t face of 1 1/4"may be used for the backing. Both edges of the gypsum board forming thehorizontal joint shall be attached to the backing with the same screws andspacing as specified in the design for the attachment of the gypsum board edges,then finished as specified for the vertical joints.• Horizontal butt joints on opposite sides of the studs in single-layerapplications should be staggered a minimum of 12 inches unless otherwisestated in the individual designs. Horizontal butt joints in adjacent layers on thesame face of the assembly in multiple-layer applications should be staggered aminimum of 12 inches unless otherwise stated in the individual designs.