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UL P522

Wood Truss

Fire Rating 1 hours
System STC n/a
System Thickness Varies

Assembly Construction

Assembly Construction

Layer 1 - Roofing System:

Any UL Class A, B or C Roofing System (TGFU) or prepared Roof Covering (TFWZ)

Layer 2 - Roof Sheathing:

Nom. 15/32" Thick Wood Structural Panels, Min. Grade "C-D" or "Sheathing"

Layer 3 - Trusses:

Pitched or Parallel Chord Wood Trusses, Spaced 24" Max. O.C., Fabricated from Nom. 2x4 Lumber, Oriented Vertically or Horizontally. Min. Truss depth shall be 5-1/4" with a Min. Roof Slope of 3/12

Layer 4 - Air Duct:

Any UL Class 0 or Class 1 Flexible Air Duct

Layer 5 - Ceiling Damper:

Max. Nom. Area, 324 SQ IN., Max. square size, 18" by 18", Rectangular sizes not to exceed 324 SQ IN. with width of 18" Max., Damper height 14" Max.

Layer 6 - Insulation:

3-1/2" Thick Min. Batts and Blankets draped over Resilient Channel and Gypsum Board Ceiling Membrane

Layer 7 - Resilient Channel:

1/2" Deep, 25ga., Installed perpendicular to the Trusses, Spaced 16" Max. O.C.

Layer 8 - 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.