UL Design U423

1-Hour Fire Rated Load-bearing steel stud wall rated 3/4, 1, 1-1/2 or 2 hours

UL Design U423 — Load-bearing steel stud wall rated 3/4, 1, 1-1/2 or 2 hours. Studs are min 3-1/2 in. deep formed from min 0.0329 in. (No. 20 MSG) galvanized steel, spaced max 24 in. o.c. (16 in. o.c. for some alternate studs). The 1-hour rating uses one layer of 5/8 in. gypsum board each side; 3/4-hour uses one layer of 1/2 in.; 1-1/2-hour uses two layers of 1/2 in.; 2-hour uses two layers of 5/8 in. each side, with nominal 2 in. mineral wool batts required for 2-hour configurations. Board is fastened with Type S-12 steel screws 8 in. o.c. at the perimeter and 12 in. o.c. in the field for single-layer systems.