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Home / Assemblies / UL W158
UL W1583-hr Fire RatingFloor/CeilingLoad-BearingSTC 41
Wood JoistGypsum BoardMineral WoolDesign

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

UL-listed 3-hour fire-rated wood joist floor/ceiling assembly. TJI wood I-joists at 24" o.c. with R-30 mineral wool, 3 layers of 5/8" Type X gypsum board ceiling.

Cross-Section Diagram

1234567FLOOR/CEILING ASSEMBLYSECTION · NOT TO SCALE7 LAYERSsee legend for ① ② ③
Legend
1Floor covering(varies)
23/4" OSB subfloor(3/4")
3TJI wood I-joists at 24" o.c.(11.875")
4R-30 mineral wool
55/8" Type X gypsum board(5/8")
65/8" Type X gypsum board(5/8")
75/8" Type X gypsum board(5/8")

Specifications

Fire Rating
3-Hour
STC Rating
STC 41
Load Bearing
Yes
Total Thickness
15.25"
Source / Publisher
UL (Underwriters Laboratories)
Design Number
W158
Assembly Type
Floor/Ceiling
Test Standard
CAN/ULC-S101
Construction Group
Light Frame
Number of Layers
7 layers

Applicable Codes

IBC 2021 §722IRC R302.1IBC 2024 §722

Construction Summary

TJI wood I-joists at 24" o.c. with R-30 mineral wool, 3 layers of 5/8" Type X gypsum board ceiling

Material Layers

LayerMaterialThickness
1Floor coveringvaries
23/4" OSB subfloor3/4"
3TJI wood I-joists at 24" o.c.11.875"
4R-30 mineral wool—
55/8" Type X gypsum board5/8"
65/8" Type X gypsum board5/8"
75/8" 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.