IBC Design 721.1(1) 1-6.5
3-Hour Fire Rated Steel columns and all of primary trusses — Perlite or vermiculite gypsum plaster over one layer of…
IBC Table 721.1(1), Item 1-6.5 (Steel columns and all of primary trusses): protection by Perlite or vermiculite gypsum plaster over one layer of 1/2" plain full-length gypsum lath applied tight to column flanges. Lath tied with doubled 0.049" (No. 18 B.W. gage) wire ties spaced 23" on center and scratch coat wrapped with 1" hexagonal mesh 0.035" (No. 20 B.W. gage) wire fabric. For three-coat work, the plaster mix for the second coat shall not exceed 100 pounds of gypsum to 2-1/2 cubic feet of aggregate. Minimum insulating material thickness — 3-hr: 2". Prescriptive protection from the adopted building code — see table footnotes for conditions.
Perlite or vermiculite gypsum plaster over one layer of 1/2" plain full-length gypsum lath applied tight to column flanges. Lath tied with doubled 0.049" (No. 18 B.W. gage) wire ties spaced 23" on center and scratch coat wrapped with 1" hexagonal mesh 0.035" (No. 20 B.W. gage) wire fabric. For…
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