IBC Design 721.1(1) 1-8.1

2-Hour Fire Rated Steel columns and all of primary trusses — Wood-fibered gypsum plaster mixed 1:1 by weight…

IBC Table 721.1(1), Item 1-8.1 (Steel columns and all of primary trusses): protection by Wood-fibered gypsum plaster mixed 1:1 by weight gypsum-to-sand aggregate applied over metal lath. Lath lapped 1" and tied 6" on center at all end, edges and spacers with 0.049" (No. 18 B.W. gage) steel tie wires. Lath applied over 1/2" spacers made of 3/4" furring channel with 2" legs bent around each corner. Spacers located 1" from top and bottom of member and not greater than 40" on center and wire tied with a single strand of 0.049" (No. 18 B.W. gage) steel tie wires. Corner bead tied to the lath at 6" on center along each corner to provide plaster thickness. Minimum insulating material thickness — 2-hr: 1-5/8". Prescriptive protection from the adopted building code — see table footnotes for conditions.