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

Understanding ULPage 4 – Metal Thickness (steel Joists)7. Steel JoistsThe specified minimum size joist in floor- or roof-ceiling designs is thejoist that meets the requirements for both the minimum depth and theminimum weight per foot. Joists that exceed the specified minimumsize may be used, provided the accessories are compatible. Thedimension from the bottom chord of joists to the ceiling, whether given orcalculated, is a minimum.Spacing between joists may be increased from that specified to amaximum of 4 ft on centers if the floor slab meets structural t requirementsand the spacing of the hanger wires supporting the ceiling is notincreased. Where it is necessary to provide support for the ceiling hangerwires between the joists, this may be accomplished by using 1-1/21/2 in., No.16 gauge or larger cold-rolled steel channels. Each channel with its weboriented vertically should be placed on top of and perpendicular to thejoist's bottom chord and tied thereto with a double strand of No. 18 SWGgalvanized steel wire.