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Home / Assemblies / UL J105
UL J1052-hr Fire RatingJoint System
Mineral WoolDesign

Head-of-Wall Joint — Cementitious System

UL-listed 2-hour fire-rated head-of-wall joint system. Head-of-Wall Joint, 1/2" max width, Cementitious mortar fill with mineral wool backer.

Cross-Section Diagram

12FIRE-RATED JOINTSECTION · NOT TO SCALE2 LAYERSsee legend for ① ② ③
Legend
1Mineral wool backer(3")
2Cementitious mortar fill(1/2")

Specifications

Fire Rating
2-Hour
Load Bearing
No
Total Thickness
Varies
Source / Publisher
UL (Underwriters Laboratories)
Design Number
J105
Assembly Type
Joint System
Test Standard
ASTM E1966
Construction Group
N/A
Number of Layers
2 layers

Applicable Codes

IBC 2024 §714IBC 2021 §715

Construction Summary

Head-of-Wall Joint, 1/2" max width, Cementitious mortar fill with mineral wool backer

Material Layers

LayerMaterialThickness
1Mineral wool backer3"
2Cementitious mortar fill1/2"

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.