B
HomeLibrariesCopilotSearchProjectsBookmarks
FeedbackHelp Desk
Libraries
Building Codes
Code LibraryIBC — BuildingIRC — ResidentialIFC — FireIPC — PlumbingIMC — MechanicalIFGC — Fuel GasIECC — EnergyNEC — ElectricalModel Codes
Specifications
CSI SpecificationsDOT SpecsTransit SpecsUSACE
Standards
TransportationRailroadFire SafetyAccessibilityStructural
Tools & References
DiagramsAssembliesProductsCalculatorsChecklistsPermits
PricingLog in
Home / Assemblies / UL L125
UL L1251-hr Fire RatingRoof/CeilingLoad-Bearing
Design

Wood Truss Roof/Ceiling — single layer 5/8" Type C gypsum board

UL-listed 1-hour fire-rated wood truss roof/ceiling assembly. 2x10 wood rafters at 16" o.c. with R-49 blown cellulose, single layer of 5/8" Type C gypsum board ceiling, 7/16" OSB sheathing.

Cross-Section Diagram

12345ROOF/CEILING ASSEMBLYSECTION · NOT TO SCALE5 LAYERSsee legend for ① ② ③
Legend
1Roof covering(varies)
27/16" OSB sheathing(7/16")
32x10 wood rafters at 16" o.c.(12"-24")
4R-49 blown cellulose
55/8" Type C gypsum board(5/8")

Specifications

Fire Rating
1-Hour
Load Bearing
Yes
Total Thickness
14.62"
Source / Publisher
UL (Underwriters Laboratories)
Design Number
L125
Assembly Type
Roof/Ceiling
Test Standard
CAN/ULC-S101
Construction Group
Light Frame
Number of Layers
5 layers

Applicable Codes

IBC 2021 §722

Construction Summary

2x10 wood rafters at 16" o.c. with R-49 blown cellulose, single layer of 5/8" Type C gypsum board ceiling, 7/16" OSB sheathing

Material Layers

LayerMaterialThickness
1Roof coveringvaries
27/16" OSB sheathing7/16"
32x10 wood rafters at 16" o.c.12"-24"
4R-49 blown cellulose—
55/8" 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.