IBC Design 721.1(1) 1-7.3

3-Hour Fire Rated Steel columns and all of primary trusses — Three layers of 5/8" Type X gypsum wallboard,1-5/8" steel…

IBC Table 721.1(1), Item 1-7.3 (Steel columns and all of primary trusses): protection by Three layers of 5/8" Type X gypsum wallboard,1-5/8" steel studs 0.018" thick (No. 25 carbon sheet steel gage) at each corner of column. Middle layer also secured with 0.049" (No. 18 B.W. gage) double-strand steel wire ties, 24" on center. Screws are No. 6 by 1" spaced 24" on center for inner layer, No. 6 by 1-5/8" spaced 12" on center for middle layer and No. 8 by 2-1/4" spaced 12" on center for outer layer. Minimum insulating material thickness — 3-hr: 1-7/8". Prescriptive protection from the adopted building code — see table footnotes for conditions.