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 D149
UL D1491-hr Fire RatingFloor/CeilingLoad-BearingSTC 49
Steel JoistDesign

Steel Joist Floor/Ceiling — single layer 5/8" Type C gypsum board

UL-listed 1-hour fire-rated steel joist floor/ceiling assembly. Open-web steel joists at 48" o.c., single layer of 5/8" Type C gypsum board ceiling.

Cross-Section Diagram

1234FLOOR/CEILING ASSEMBLYSECTION · NOT TO SCALE4 LAYERSsee legend for ① ② ③
Legend
1Floor covering(varies)
22-1/2" lightweight concrete on steel deck(2-1/2")
3Open-web steel joists at 48" o.c.(14.0")
45/8" Type C gypsum board(5/8")

Specifications

Fire Rating
1-Hour
STC Rating
STC 49
Load Bearing
Yes
Total Thickness
16.12"
Source / Publisher
UL (Underwriters Laboratories)
Design Number
D149
Assembly Type
Floor/Ceiling
Test Standard
CAN/ULC-S101
Construction Group
Non-Combustible
Number of Layers
4 layers

Applicable Codes

IBC 2021 Table 722.1IBC 2024 §722

Construction Summary

Open-web steel joists at 48" o.c., single layer of 5/8" Type C gypsum board ceiling

Material Layers

LayerMaterialThickness
1Floor coveringvaries
22-1/2" lightweight concrete on steel deck2-1/2"
3Open-web steel joists at 48" o.c.14.0"
45/8" Type C 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.