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 D168
UL D1684-hr Fire RatingFloor/CeilingLoad-BearingSTC 39
Steel JoistFiberglass BattDesign

Steel Joist Floor/Ceiling — 3 layers Spray-applied fireproofing

UL-listed 4-hour fire-rated steel joist floor/ceiling assembly. Open-web steel joists at 48" o.c. with R-19 fiberglass batt, 3 layers of Spray-applied fireproofing ceiling.

Cross-Section Diagram

1234567FLOOR/CEILING ASSEMBLYSECTION · NOT TO SCALE7 LAYERSsee legend for ① ② ③
Legend
1Floor covering(varies)
22" concrete on steel deck(2")
3Open-web steel joists at 48" o.c.(14.0")
4R-19 fiberglass batt
5Spray-applied fireproofing(1-1/2")
6Spray-applied fireproofing(1-1/2")
7Spray-applied fireproofing(1-1/2")

Specifications

Fire Rating
4-Hour
STC Rating
STC 39
Load Bearing
Yes
Total Thickness
20"
Source / Publisher
UL (Underwriters Laboratories)
Design Number
D168
Assembly Type
Floor/Ceiling
Test Standard
ASTM E119
Construction Group
Non-Combustible
Number of Layers
7 layers

Applicable Codes

IBC 2024 Table 722.1

Construction Summary

Open-web steel joists at 48" o.c. with R-19 fiberglass batt, 3 layers of Spray-applied fireproofing ceiling

Material Layers

LayerMaterialThickness
1Floor coveringvaries
22" concrete on steel deck2"
3Open-web steel joists at 48" o.c.14.0"
4R-19 fiberglass batt—
5Spray-applied fireproofing1-1/2"
6Spray-applied fireproofing1-1/2"
7Spray-applied fireproofing1-1/2"

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.