UL Design L528

1-Hour Fire Rated Wood Truss Floor-Ceiling — gypsum topping + resilient channels, STC 56

UL Design L528 — 1-hour wood truss floor-ceiling. Parallel-chord wood trusses at 24" o.c. with 23/32" structural panel subfloor and 3/4" gypsum floor topping; 3-1/2" glass fiber or mineral wool in the cavity; ceiling of 5/8" Type X gypsum board on resilient channels. Tested STC 56 with carpet finish per National Gypsum (NGC-5026005_R1).

Parallel-chord trusses @ 24" o.c., 3/4" gypsum topping on 23/32" panel, RC + 5/8" Type X ceiling; STC 56

The full text is for BuildSpec members

Read the complete section, search across every adopted code, run the calculators and ask Copilot — free for 14 days, no card required.

  • Layer-by-layer components with thicknesses
  • Cross-section diagram
  • Applicable code sections and test standard
  • 6 related assemblies
Start your free 14-day trialSign in →