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Home / Assemblies / UL L145
UL L1453-hr Fire RatingRoof/CeilingLoad-Bearing
Gypsum BoardDesign

Wood Truss Roof/Ceiling — 2 layers 5/8" Type C gypsum board

UL-listed 3-hour fire-rated wood truss roof/ceiling assembly. 2x12 wood rafters at 24" o.c. with R-49 blown cellulose, 2 layers of 5/8" Type C gypsum board ceiling, 5/8" plywood sheathing.

Cross-Section Diagram

123456ROOF/CEILING ASSEMBLYSECTION · NOT TO SCALE6 LAYERSsee legend for ① ② ③
Legend
1Roof covering(varies)
25/8" plywood sheathing(5/8")
32x12 wood rafters at 24" o.c.(12"-24")
4R-49 blown cellulose
55/8" Type C gypsum board(5/8")
65/8" Type C gypsum board(5/8")

Specifications

Fire Rating
3-Hour
Load Bearing
Yes
Total Thickness
15.25"
Source / Publisher
UL (Underwriters Laboratories)
Design Number
L145
Assembly Type
Roof/Ceiling
Test Standard
UL 263
Construction Group
Light Frame
Number of Layers
6 layers

Applicable Codes

IBC 2024 Table 722.1NFPA 5000

Construction Summary

2x12 wood rafters at 24" o.c. with R-49 blown cellulose, 2 layers of 5/8" Type C gypsum board ceiling, 5/8" plywood sheathing

Material Layers

LayerMaterialThickness
1Roof coveringvaries
25/8" plywood sheathing5/8"
32x12 wood rafters at 24" o.c.12"-24"
4R-49 blown cellulose—
55/8" Type C gypsum board5/8"
65/8" Type C gypsum board5/8"

Important Notice

This assembly listing is for reference only. Always verify against the current UL Product iQ database before specifying in construction documents. Material substitutions may void the fire rating. Consult with a qualified fire protection engineer for project-specific requirements.