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Home / Assemblies / UL D104
UL D1041.5-hr Fire RatingFloor/CeilingLoad-BearingSTC 45
Steel JoistFiberglass BattDesign

Steel Joist Floor/Ceiling — single layer 5/8" Type C gypsum board

UL-listed 1.5-hour fire-rated steel joist floor/ceiling assembly. Open-web steel joists at 24" o.c. with R-19 fiberglass batt, single layer of 5/8" Type C gypsum board ceiling.

Cross-Section Diagram

12345FLOOR/CEILING ASSEMBLYSECTION · NOT TO SCALE5 LAYERSsee legend for ① ② ③
Legend
1Floor covering(varies)
22" concrete on steel deck(2")
3Open-web steel joists at 24" o.c.(14.0")
4R-19 fiberglass batt
55/8" Type C gypsum board(5/8")

Specifications

Fire Rating
1.5-Hour
STC Rating
STC 45
Load Bearing
Yes
Total Thickness
16.12"
Source / Publisher
UL (Underwriters Laboratories)
Design Number
D104
Assembly Type
Floor/Ceiling
Test Standard
ASTM E119
Construction Group
Non-Combustible
Number of Layers
5 layers

Applicable Codes

IBC 2021 §722IBC 2024 §722

Construction Summary

Open-web steel joists at 24" o.c. with R-19 fiberglass batt, single layer of 5/8" Type C gypsum board ceiling

Material Layers

LayerMaterialThickness
1Floor coveringvaries
22" concrete on steel deck2"
3Open-web steel joists at 24" o.c.14.0"
4R-19 fiberglass batt—
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.