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UL G556

Steel C-Joist (Load-Bearing)

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

CAD/Revit & Acoustics

Assembly Construction

Assembly Construction

Layer 1 - Subfloor Topping Mixture:

3/4" Thick Levelrock® Brand 4500 Series Floor Underlayments

Layer 2 - Sound Mat (Optional):

1/4" Thick Levelrock® Brand SRM-25™ Ready Seam™ Sound Reduction Mat

Layer 3 - Structural Cement-Fiber Units:

3/4" Thick USG Structural Panel Concrete Subfloor (UL Type USGSP)

Layer 4 - Steel Joists:

Channel-Shaped, 10" Deep Min., 16 Ga., Spaced 24" Max. O.C.

Layer 5 - Clip Angles (Not Shown):

One Clip Angle Per Joist End

Layer 6 - Joist Bridging (Not Shown):

V-Bracing of 1-1/2", 20 Ga., Galvanized Steel Between Channels

Layer 7 - Insulation:

3-5/8" Thick Glass Fiber Batt Insulation

Layer 8 - Steel Framing Members:

Suspension System May be Used in Lieu of the Resilient Channels. Main Runners, Cross Tees, Cross Channels and Wall Angle as Listed Below (UL Type DGL):

Layer 9 - Main Runners:

4' O.C. Main Runners Suspended by 12 ga. Min. Hanger Wire, 16" O.C.

Layer 10 - Cross Tees:

16" O.C.

Layer 11 - Cross Channels:

16" O.C.

Layer 12 - Wall Angle or Channel:

Painted or Galvanized Steel Angle to Support Steel Framing Member Ends and for Screw-Attachment of the Gypsum Panel (UL Type DGL)

Layer 13 - Gypsum Board:

5/8" Thick Gypsum Board (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.