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UL P561

Steel C-Joist (Load-Bearing)

Fire Rating 2 hours
System STC n/a
System IIC null
System Thickness Varies

Assembly Construction

Assembly Construction

Layer 1 - Roof Covering:

1 layer Ballasted, adhered or mechanically attached to the Insulation; Hot-mopped or cold-application, Class A, B or C Covering or Single-Ply Membrane

Layer 2 - Roofing Membrane:

1 layer Single-Ply Membrane: Ballasted, adhered or mechanically attached to Structural Cement-Fiber Units

Layer 3 - 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 4 - Steel Joists:

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

Layer 5 - Clip Angles (Not Shown):

1 layer One Clip Angle per Joist End

Layer 6 - Air Space:

1 layer 4" Min. between bottom flange of Joist and Main Runners

Layer 7 - Insulation:

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

Layer 8 - Steel Framing Members:

1 layer Listed Below (UL Type DGL):

Layer 9 - Main Runners:

1 layer 4' O.C. Main Runners suspended by 12ga. Min. Hanger Wire, 24" O.C.

Layer 10 - Cross Tees:

1 layer 16" O.C.

Layer 11 - Cross Channels:

1 layer 16" O.C.

Layer 12 - 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.