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Home / Assemblies / UL D142
UL D1424-hr Fire RatingFloor/CeilingLoad-BearingSTC 38
Steel JoistGypsum BoardDesign

Steel Joist Floor/Ceiling — 3 layers 5/8" Type X gypsum board

UL-listed 4-hour fire-rated steel joist floor/ceiling assembly. C-channel steel joists at 16" o.c., 3 layers of 5/8" Type X gypsum board ceiling.

Cross-Section Diagram

123456FLOOR/CEILING ASSEMBLYSECTION · NOT TO SCALE6 LAYERSsee legend for ① ② ③
Legend
1Floor covering(varies)
23" concrete on steel deck(3")
3C-channel steel joists at 16" o.c.(10.0")
45/8" Type X gypsum board(5/8")
55/8" Type X gypsum board(5/8")
65/8" Type X gypsum board(5/8")

Specifications

Fire Rating
4-Hour
STC Rating
STC 38
Load Bearing
Yes
Total Thickness
13.38"
Source / Publisher
UL (Underwriters Laboratories)
Design Number
D142
Assembly Type
Floor/Ceiling
Test Standard
CAN/ULC-S101
Construction Group
Non-Combustible
Number of Layers
6 layers

Applicable Codes

IBC 2021 §722IBC 2024 §722NFPA 5000

Construction Summary

C-channel steel joists at 16" o.c., 3 layers of 5/8" Type X gypsum board ceiling

Material Layers

LayerMaterialThickness
1Floor coveringvaries
23" concrete on steel deck3"
3C-channel steel joists at 16" o.c.10.0"
45/8" Type X gypsum board5/8"
55/8" Type X gypsum board5/8"
65/8" Type X 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.