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Home / Assemblies / UL W155
UL W1552-hr Fire RatingFloor/CeilingLoad-BearingSTC 42
Wood JoistGypsum BoardDesign

Wood Joist Floor/Ceiling — 2 layers 5/8" Type C gypsum board

UL-listed 2-hour fire-rated wood joist floor/ceiling assembly. TJI wood I-joists at 24" o.c., 2 layers 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)
23/4" plywood subfloor(3/4")
3TJI wood I-joists at 24" o.c.(11.875")
45/8" Type C gypsum board(5/8")
55/8" Type C gypsum board(5/8")

Specifications

Fire Rating
2-Hour
STC Rating
STC 42
Load Bearing
Yes
Total Thickness
14.62"
Source / Publisher
UL (Underwriters Laboratories)
Design Number
W155
Assembly Type
Floor/Ceiling
Test Standard
UL 263
Construction Group
Light Frame
Number of Layers
5 layers

Applicable Codes

IBC 2021 Table 722.1IRC R302.1IBC 2024 Table 722.1

Construction Summary

TJI wood I-joists at 24" o.c., 2 layers of 5/8" Type C gypsum board ceiling

Material Layers

LayerMaterialThickness
1Floor coveringvaries
23/4" plywood subfloor3/4"
3TJI wood I-joists at 24" o.c.11.875"
45/8" Type C gypsum board5/8"
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.