UL Design U420
1-Hour Fire Rated Double-Row Steel Stud Chase Wall — high STC
UL Design U420 — non-bearing chase wall on paired rows of 1-5/8" steel studs. 1-hour: one layer of 5/8" Type X each side with 2-1/2" insulation, tested STC 55 (NRC-93-300). 2-hour: two layers of 5/8" Type X each side, tested STC 65 (NRC-93-321) — one of the highest tested STC values among standard gypsum partitions. Per CertainTeed Fire Resistance and Sound Control Design Manual.
Paired 1-5/8" steel stud rows (chase), 5/8" Type X each side, 2-1/2" insulation; STC 55 (1-hr) / 65 (2-hr)
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- Layer-by-layer components with thicknesses
- Cross-section diagram
- Applicable code sections and test standard
- 6 related assemblies