FIRE RATED STEEL STUD FRAMING SYSTEMS: ASSEMBLIES AND SPECIFICATIONS

Fire resistance is a fundamental requirement in commercial building design. The Alberta Building Code (ABC) mandates specific fire resistance ratings for walls, floors, and ceilings based on the building's occupancy classification, construction type, and the location of the assembly within the building. For interior partition walls in commercial buildings, fire resistance ratings of 1-hour, 1.5-hour, and 2-hour are most common. Steel stud framing, combined with specific types and layers of gypsum board, is the standard method for achieving these ratings in commercial construction throughout Edmonton and Alberta.

HOW FIRE RESISTANCE IS MEASURED

Fire resistance ratings are determined through standardized testing conducted in accordance with CAN/ULC-S101 (Standard Methods of Fire Endurance Tests of Building Construction and Materials) in Canada, or ASTM E119 in the United States. During a fire endurance test, the assembly is exposed to a standardized time-temperature curve in a furnace. The assembly passes the test if it maintains its structural integrity, prevents the passage of flame and hot gases, and limits the temperature rise on the unexposed face to a specified maximum for the duration of the rated period.

UL-LISTED ASSEMBLY DESIGNS

The most widely used reference for fire-rated steel stud framing assemblies in Canada is the UL Fire Resistance Directory, published by Underwriters Laboratories. The UL directory contains thousands of tested and listed assembly designs, each identified by a unique design number (e.g., UL Design U305, U419, W401). Each design specifies the exact components and installation requirements for the assembly, including stud size and gauge, stud spacing, drywall type and thickness, number of drywall layers, fastener type and spacing, and joint treatment.

It is critical that fire-rated assemblies be installed exactly as specified in the UL design. Any deviation from the listed design — such as using a different stud gauge, a different drywall type, or a different fastener pattern — may void the fire rating. Building inspectors in Edmonton are trained to verify UL design compliance during framing and drywall inspections.

COMMON FIRE-RATED ASSEMBLY DESIGNS

1-Hour Rated Partitions (UL U305): One of the most common fire-rated partition assemblies in commercial construction. Consists of 3-5/8" 25-gauge steel studs at 24" o.c. with one layer of 5/8" Type X gypsum board on each side. Total wall thickness is approximately 4-7/8". This assembly is suitable for corridor walls, tenant demising walls, and other locations requiring a 1-hour fire rating.

2-Hour Rated Partitions (UL U419): Requires two layers of 5/8" Type X gypsum board on each side of 3-5/8" 20-gauge studs at 24" o.c. Total wall thickness is approximately 6-1/8". Used for stairwell enclosures, elevator shaft walls, and other locations requiring a 2-hour fire rating.

FIRESTOPPING AT PENETRATIONS

Fire-rated walls must be maintained as continuous fire barriers. Any penetration through a fire-rated wall — for conduit, pipe, duct, or cable — must be firestopped with a listed firestop system that maintains the fire resistance rating of the wall. Firestop systems are also listed in the UL directory and must be installed by qualified tradespeople in accordance with the listing requirements.

GoldStar Builders Corporation specializes in fire-rated drywall and framing assemblies for commercial projects in Edmonton. Their crews are trained in UL-listed assembly installation and work closely with building inspectors to ensure code compliance. Learn more at goldstarbuilders.ca/fire-rated-drywall.