B
HomeLibrariesCopilotSearchProjectsBookmarks
FeedbackHelp Desk
Libraries
Building Codes
Code LibraryIBC — BuildingIRC — ResidentialIFC — FireIPC — PlumbingIMC — MechanicalIFGC — Fuel GasIECC — EnergyNEC — ElectricalModel Codes
Specifications
CSI SpecificationsDOT SpecsTransit SpecsUSACE
Standards
TransportationRailroadFire SafetyAccessibilityStructural
Tools & References
DiagramsAssembliesProductsCalculatorsChecklistsPermits
PricingLog in
Home / Assemblies / UL C126
UL C1261-hr Fire RatingJoint System
Mineral WoolDesign

Through-Penetration Firestop — Cementitious System

UL-listed 1-hour fire-rated through-penetration firestop system. Through-Penetration Firestop, 1" 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(1")
2Cementitious mortar fill(1/2")

Specifications

Fire Rating
1-Hour
Load Bearing
No
Total Thickness
Varies
Source / Publisher
UL (Underwriters Laboratories)
Design Number
C126
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

Through-Penetration Firestop, 1" max width, Cementitious mortar fill with mineral wool backer

Material Layers

LayerMaterialThickness
1Mineral wool backer1"
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.