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Home / Assemblies / UL W128
UL W1284-hr Fire RatingFloor/CeilingLoad-BearingSTC 56
Wood JoistGypsum BoardHigh STCDesign

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

UL-listed 4-hour fire-rated wood joist floor/ceiling assembly. 2x12 wood 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)
23/4" plywood subfloor(3/4")
32x12 wood joists at 16" o.c.(11.25")
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 56
Load Bearing
Yes
Total Thickness
14.62"
Source / Publisher
UL (Underwriters Laboratories)
Design Number
W128
Assembly Type
Floor/Ceiling
Test Standard
ASTM E119
Construction Group
Light Frame
Number of Layers
6 layers

Applicable Codes

IBC 2024 Table 722.1IBC 2024 §722

Construction Summary

2x12 wood joists at 16" o.c., 3 layers of 5/8" Type X gypsum board ceiling

Material Layers

LayerMaterialThickness
1Floor coveringvaries
23/4" plywood subfloor3/4"
32x12 wood joists at 16" o.c.11.25"
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.