What would happen if the steel framing materials you use had not been manufactured to accepted standards? The proper manufacturing of steel is critical to ensuring a quality building product. Any shortcuts or failures to meet specifications and tolerances would compromise your construction project.
Module 2: Steel Framing Materials of AWCI’s Steel—Doing It Right® describes the technology used during the manufacturing process and the tolerances and specifications that ensure quality cold-formed steel framing (CFS). It discusses the protective coatings for steel. It also describes the nomenclature and identification of framing materials as well as the product designation system.
Steel-Making Technologies
SFIA-member steel mills use two technologies to make steel — the basic oxygen furnace and the electric arc furnace. The electric arc furnace uses primarily recycled steel to create new steel, offering significant sustainability benefits.
A Nucor electric arc furnace. Photo courtesy: Nucor
After it leaves the furnace, the iron still contains impurities such as silicon, nitrogen, sulfur and excess carbon that can make it brittle. Then alloying elements such as nickel vanadium manganese are added to produce different grades of steel. Modern technology allows the steel maker to create steel according to the desired recipe with great precision.
CFS Protective Coatings
Zinc is the coating most commonly used when manufacturing steel. Standards require minimum coating thicknesses.
- Non-structural members require a G40 minimum or equivalent
- Structural members require a G60 minimum or equivalent
During construction or during handling, galvanized steel often gets scratched, rubbed up against other things or dragged across the ground through the water. But here’s an interesting fact: No rust can happen adjacent to the coating. If there are scratches or scrapes on the member, the galvanic action actually causes that coating to move into the area of the scratches and bridge any gaps. It’s only when you have a very wide damaged area, a very thin zinc coating or prolonged exposure to moisture that you run into problems.
Steel coil ready for shipment to the CFS manufacturer.
About AWCI’s Steel—Doing It Right
The Association of Walls and Ceilings Industry has developed a program called Steel—Doing It Right® to provide a thorough introduction to the information a contractor needs to effectively estimate, plan and deliver on a project where cold-formed steel (CFS) is used.
By taking this AWCI course, participants can learn about CFS construction best practices, tap the market opportunity for CFS framing and increase their potential for business growth.
While the course is not a certification program, each seminar participant receives a certificate of attendance. Attending engineers are eligible for 9 Professional Development hours, and 9 LU hours are available for AIA credit via the AIA “Self-Report” option.
CFS Roll Forming
After the steel has been made, coated and coiled, the manufacturer ships the coils to service centers. CFS manufacturers buy the coils from the service centers, and the purchased coils are sent to their roll-former facilities to create CFS studs, track, hat channels and other members for construction use.
Steel being rolled into studs and stamped with product information.
Very tight tolerances are used in the roll-forming process, almost eliminating all waste. The forming machines shape the members to meet proper specifications. Studs can be custom cut, which helps to reduce labor costs on the job.
The finished CFS products are sold through building suppliers and distributors.
CFS Manufacturing Tolerances
Manufacturers must meet specific tolerances during the manufacturing process. These tolerances are detailed in the standards.
The American Iron and Steel Institute (AISI) S100-16(R2020) w/S3-22: North American Specification for the Design of Cold-Formed Steel Structural Members provides requirements for the fabrication of the members.
The AISI S240 provides specific requirements for CFS structural framing. The AISI S220 provides the standards for non-structural steel framing. Download these publications for free here.
The steel industry is transitioning from ASTM to AISI standards, and the 2018 International Building Code reflects this change. While ASTM is still referenced widely in the 2018 IBC, it is not referenced relative to CFS framing. The 2018 IBC references AISI S220 for nonstructural CFS framing products and AISI S240 for structural CFS framing products. Older IBC editions reference ASTM C645 for non-structural CFS framing products, ASTM C955 for structural CFS framing products.
Stickers, Stamps, Embossing
Look for CFS product identification information on members delivered to a job site. This information can be applied via a sticker, a stamp or embossing.
SFIA certification labels identify quality steel studs. Photo courtesy: CEMCO
CFS product identification should contain:
- 54 is the material thickness
- G 60 indicates the coating thickness
- 50 ksi is the yield strength
- The final letters and numbers identifies the manufacturer
- NS must be include if the product is a non-structural stud
Mill Certifications
How does a manufacturer of CFS know what he’s getting when he buys the steel coil? The supplier provides the manufacturer with a mill certificate.
The mill certificate certifies that tests have been done to verify thickness, yield strength, total elongation, chemical requirements and galvanized coating. A mill certificate may be required in the contract documents as a submittal during construction. Be sure to ask for the mill certificate upfront when you place your order.
Nomenclature and Product Designation
At one time manufacturers produced a wide variety of steel framing members. So the industry developed a universal product designator system.
This system is used by Steel framing Industry Association (SFIA) members who produce 85% of the steel stud and track in the United States. So this system is in common use. It is known as “The Right Stuff,” where stuff is actually STUFL.
The Right STUFL
- S is for a stud or joist with stiffening lips
- T represents track sections
- U denotes the cold roll channel CRC or U channels
- F stands for furring channels, also known as hat channels
- L designates an L header or angle
CFS Product Designator
Let’s take an example. The product designator 362 S 162-54 has four parts:
- Member or web depth: 362 indicates a 3 and 5/8 inch wide stud
- Style: The letter S represents the type of member — a stud or joist
- Flange width: 162 indicates the flange size of 1 and 5/8 inches
- Material Thickness: 54 indicates the base steel thickness in mils
Note that non-structural framing members must also have an “NS” as part of their designator marking on the stud.
Material of Choice for Mid-Rise Construction
Module 2 of AWCI’s Steel—Doing It Right has more information to help participants identify the technologies used in steel production, describe the steel framing manufacturing process and the protective coatings applied to protect CFS members from corrosion, know the standards governing the tolerances for CFS products and understand the nomenclature used to describe them.
CFS is the material of choice for mid-rise load-bearing construction for many reasons, among them being that it’s lightweight, noncombustible, strong and straight.
Article cited from BuildSteel