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Home / Assemblies / UL L171
UL L1713-hr Fire RatingRoof/CeilingLoad-Bearing
Steel JoistDesign

Steel Truss Roof/Ceiling — 3 layers Spray-applied fireproofing

UL-listed 3-hour fire-rated steel truss roof/ceiling assembly. Steel bar joists at 24" o.c. with Rigid insulation board, 3 layers of Spray-applied fireproofing ceiling, 22 ga. steel deck.

Cross-Section Diagram

1234567ROOF/CEILING ASSEMBLYSECTION · NOT TO SCALE7 LAYERSsee legend for ① ② ③
Legend
1Roof covering(varies)
222 ga. steel deck(varies)
3Steel bar joists at 24" o.c.(12"-24")
4Rigid insulation board
5Spray-applied fireproofing(1-1/2")
6Spray-applied fireproofing(1-1/2")
7Spray-applied fireproofing(1-1/2")

Specifications

Fire Rating
3-Hour
Load Bearing
Yes
Total Thickness
18.5"
Source / Publisher
UL (Underwriters Laboratories)
Design Number
L171
Assembly Type
Roof/Ceiling
Test Standard
ASTM E119
Construction Group
Non-Combustible
Number of Layers
7 layers

Applicable Codes

IRC R302.1IBC 2024 §722

Construction Summary

Steel bar joists at 24" o.c. with Rigid insulation board, 3 layers of Spray-applied fireproofing ceiling, 22 ga. steel deck

Material Layers

LayerMaterialThickness
1Roof coveringvaries
222 ga. steel deckvaries
3Steel bar joists at 24" o.c.12"-24"
4Rigid insulation board—
5Spray-applied fireproofing1-1/2"
6Spray-applied fireproofing1-1/2"
7Spray-applied fireproofing1-1/2"

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.