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UL P561

Steel C-Joist (Load-Bearing)

Fire Rating 1.5 hours
System STC n/a
System IIC null
System Thickness Varies

Assembly Construction

Assembly Construction

Layer 1 - Roof Covering:

1 layer 5/8" Thick Gypsum Fiber Roof Board (UL Type FRX-G™)

Layer 2 - Structural Cement-Fiber Units:

1 layer 3/4" Thick, USG Structural Panel Concrete Subfloor (USGSP), with long edges tongue and grooved, long dimension of panels to be perpendicular to Joists (UL Type USGSP)

Layer 3 - Steel Joists:

1 layer 10" Deep, 16ga., Spaced 24" Max. O.C.

Layer 4 - Clip Angles (Not Shown):

1 layer One Clip Angle per Joist End

Layer 5 - Insulation:

1 layer 3-1/2" Thick Glass Fiber Batt Insulation

Layer 6 - Resilient Channel:

1 layer 1/2" 25ga. Resilient Channel Spaced 16" O.C.

Layer 7 - Gypsum Panel:

1 layer 5/8" [15.9 mm] Sheetrock® EcoSmart Gypsum Panel (UL Type ULIX™)


  • For the most up-to-date fire-resistance ratings, refer to the UL Online Certifications Directory.
  • Estimated range of acoustical performance is based on laboratory test data of similarly constructed assemblies.