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Home / Assemblies / UL D133
UL D1332-hr Fire RatingFloor/CeilingLoad-BearingSTC 51
Steel JoistGypsum BoardDesign

Steel Joist Floor/Ceiling — 2 layers 5/8" Type X gypsum board

UL-listed 2-hour fire-rated steel joist floor/ceiling assembly. C-channel steel joists at 16" o.c., 2 layers of 5/8" Type X gypsum board ceiling.

Cross-Section Diagram

12345FLOOR/CEILING ASSEMBLYSECTION · NOT TO SCALE5 LAYERSsee legend for ① ② ③
Legend
1Floor covering(varies)
22-1/2" concrete on steel deck(2-1/2")
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")

Specifications

Fire Rating
2-Hour
STC Rating
STC 51
Load Bearing
Yes
Total Thickness
12.75"
Source / Publisher
UL (Underwriters Laboratories)
Design Number
D133
Assembly Type
Floor/Ceiling
Test Standard
CAN/ULC-S101
Construction Group
Non-Combustible
Number of Layers
5 layers

Applicable Codes

IBC 2021 §722IBC 2021 Table 722.1IBC 2024 §722

Construction Summary

C-channel steel joists at 16" o.c., 2 layers of 5/8" Type X gypsum board ceiling

Material Layers

LayerMaterialThickness
1Floor coveringvaries
22-1/2" concrete on steel deck2-1/2"
3C-channel steel joists at 16" o.c.10.0"
45/8" Type X gypsum board5/8"
55/8" 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.