FAQ on Cold-Formed Steel

Here are answers to many common questions about steel framing. These questions are organized by subject but you may find the subject you’re interested more quickly by conducting a simple search. If you use Explorer as your browser, just press Control and the “F” key at the same time (Ctrl+F), then type in the word or words that describe the subject about which you would like more information.

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• General Technical Questions
• Wall Members and Systems
• Corrosion
• Definitions

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Question: Does steel framing product need to have some approval on them or anyone can buy the production line and manufacture the studs and track according to the building codes and materials of let's say the city of Los Angeles CA? What does it take to become a manufacturer of steel framing?

Answer: There is no specific process for becoming a manufacturer of steel framing, and there are several levels of manufacturers out there. At one end of the spectrum are the manufacturers who have bought a machine, and begin rolling material from coils or forming material on a brake press. Some of these manufacturers have no quality control program, no testing program, and sometimes buy their coils and sheets without mill certifications or test reports. On the other end of the spectrum, members of the Steel Stud Manufacturers Association (SSMA) are required to maintain an in-house quality control program, turn in annual audits, and have all of their material either mill certified or tested. Also, all material is required to be marked in accordance with the applicable building code. The marking requirements are different for different codes, but all require some form of marking.

The real question is what sort of requirements are in place in the specific jurisdiction where you are interested in installing your framing members. You mention the city of Los Angeles: they require specific research reports and verification calculations be submitted, and will issue a research report such as the one issued to SSMA (http://www.ssma.com/cola_2004.pdf). Other jurisdictions may require nothing other than a manufacturer's material certification, stating that the material complies with code. The American Iron and Steel Institute has developed a series of standards that have been adopted into the building code. The AISI's Standard for Cold-Formed Steel Framing - General Provisions gives a list of some of the requirements for framing members: compliance with specific ASTM standards, manufacturing tolerances, marking requirements, and corrosion protection. This is a start. From there, you should check with the specific jurisdiction to see what additional requirements are in place before framing materials may be used in a structure.

Although not a code requirement in all jurisdictions, I strongly urge you to set up a quality control program for your incoming material and manufacture, if you are considering manufacturing steel framing. Guidelines for this program are available from the International Code Council Evaluation Service at http://www.icc-es.org/Criteria/index.cfm. The Acceptance Criteria that apply to framing members are AC10 and AC46. Note that the SSMA does not provide guidelines for setting up framing operations, and in fact does not admit members unless they have already been manufacturing and selling steel framing for at least two years. There is an association for rollformers that may be able to give you additional information on equipment and manufacturing: the Fabricators & Manufacturers Association, at www.fmanet.org.

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Question: Where can one find additional information regarding header design?

Answer: For addition information regarding header design, additional design information can be found by contacting the Center for Cold-Formed Steel Structures, [email protected] or the Steel Framing Alliance technical hotline, 1-800-79 STEEL.

Question: Are there specific provisions in the 2003 IBC for the anchorage of load bearing exterior and non load bearing exterior light gage metal walls to the foundation? What do you recommend?

Answer: There are not specific provisions in the International Code Council's International Building Code (IBC) for anchorage of cold-formed steel framed walls; but there are provisions in the International Residential Code (IRC) for these walls. The IRC not only has details for this connection, but references the Standard for Cold-Formed Steel Framing - Prescriptive Method (AISI 2001) for anchorage, which is typically anchor bolts through the bottom track at 4' on center. For non-prescriptive construction, there are several different methods for wall anchorage that are acceptable depending upon the load and the seismic zone. The most common method is powder actuated pins. Companies like Hilti and ITW Ramset have technical data on the holding power in structural steel and concrete; for the bearing in cold-formed steel, use the bolt bearing equations in chapter E of the North American Specification for the Design of Cold-Formed Steel Structures (AISI, 2001). These also may be used for other anchorage to concrete, such as expansion bolts, threaded anchors (such as Tapcon and Kwik-Con,) Spike anchors by Powers Rawl, and others. Recent developments in epoxy anchors have made them very popular with cold-formed steel framing; they can be installed in the exact location required, and the edge distance and spacing restrictions are less than the expansion anchors.

Question: Must an L-header extend over and be attached to each king stud if there are multiple king studs?

Answer: No. The Standard for Cold-Formed Steel Framing - Header Design only requires that the L-header lap over one bearing stud at each end.

Question: In certain applications, such as with two adjacent windows, it is desired to run one header over both openings. How would such a multi-span header be designed?

Answer: The Standard for Cold-Formed Steel Framing - Header Design applies only to single-span conditions. Multi-span headers would need to be designed in accordance with the AISI North American Specification for the Design of Steel Structural Members.

Question: How do I calculate the deflection of a header beam?

Answer: According to the Commentary on the Standard for Cold-Formed Steel Framing - Header Design, a conservative estimate of the vertical deflection of back-to-back or box headers can be based on the full moment of inertia of the two C-shape sections alone. The procedure to calculate the vertical deflection of an L-header is undefined because the L-header is an indeterminate assembly consisting of two angles, cripple studs, and track sections interconnected by self-drilling screws. However, the test results indicate that the measured deflections at an applied load that equal to the design load was less than L/240, which should be acceptable in most applications.

Question: What load combinations are appropriate for the design of a header?

Answer: The Commentary to the Standard for Cold-Formed Steel Framing - Prescriptive Method for One and Two Family Dwellings provides a detailed description of the loads, load combinations and design checks that are appropriate for headers. The appropriate load combinations are:

Question: When assembling a back-to-back or box header, must the track directly beneath the C-shaped sections face up or down?

Answer: The Standard for Cold-Formed Steel Framing - Header Design allows the track directly beneath the C-shaped sections to face either way. Typically, the track would face down when cripple studs and a head track are used to frame the opening and would face up when the opening extends to the bottom side of the header beam and no cripple studs and separate head track are needed.

Question: When using steel framing in fire rated wall systems, is the thickness of the steel the minimum, or the maximum? I understand that steel transmits heat, so I thought that the thickness shown might be the maximum.

Answer: Each type of header offers certain advantages and disadvantages; however, the relatively new L-header offers significant material, fabrication and installation savings. Due primarily to the limitations of the testing that has been performed; the Standard for Cold-Formed Steel Framing - Header Design limits L-headers to a maximum span of 16 feet. L-headers also have limited uplift capacity and, therefore, may not be suitable for certain high wind areas.

Question: Can the moment capacity of the header beam be based on a composite section of the C-shape sections plus the track above the header beam, the track beneath the header beam, and/or the cripple studs and head track beneath the header beam?

Answer: The Standard for Cold-Formed Steel Framing - Header Design requires a track section above and beneath the C-shape sections and prescribes their connection to the C-shape sections with 2 No. 8 screws at 24" on center. Intentionally, this screw spacing does not provide adequate restraint to sufficiently engage the track sections to act compositely with the C-shape sections. This would require a much closer and cost prohibitive screw spacing and would need to be designed in accordance with the AISI North American Specification for the Design of Steel Structural Members.

Question: Why doesn't the Standard for Cold-Formed Steel Framing - Prescriptive Method for One and Two Family Dwellings seem to require a check for wind uplift on back-to-back or box headers?

Answer: Within the applicability limits of the Prescriptive Method, uplift due to wind was checked and was found to never control the selection of back-to-back or box headers. Therefore, the tables only consider gravity loads.

Question: Must my header design conform to the design rules contained in the Standard for Cold-Formed Steel Framing - Header Design?

Answer: Yes. The Standard for Cold-Formed Steel Framing - Header Design has been adopted by reference in the 2003 ICC and NFPA building codes and thus is legally required when the local building code adopts the these building codes. Headers that fall outside the applicability limits of the limitations of the Header Design standard must be designed in accordance with the AISI North American Specification for the Design of Steel Structural Members.

Question: When using steel framing in fire rated wall systems, is the thickness of the steel the minimum, or the maximum? I understand that steel transmits heat, so I thought that the thickness shown might be the maximum.

Answer: The thickness shown in the UL listings is the minimum. See the info from the UL website below on cold-formed steel framing.

Question: In the UL listings for fire ratings, the thickness is given in gauge. I know that some of the tests were done many years ago, and thicknesses and tolerances may have changed. Are the thicknesses still current?

Answer: In the UL listings for fire ratings, the thickness is given in gauge. I know that some of the tests were done many years ago, and thicknesses and tolerances may have changed. Are the thicknesses still current?

Steel Studs

The dimensions and gauge of steel studs are minimums. The hourly ratings apply when the steel studs are of a heavier gauge and/or larger dimensions than specified in a Design. The superimposed load of bearings walls utilizing steel studs shall be based on the capacity of the studs as determined by the 1986 edition of the AISI Specification for the Design of Cold Formed Steel Structural Members with the December 11, 1989 Addendum.

Metal Thickness

Unless otherwise indicated in the individual designs, the following minimum metal thickness tables shall apply where a metal gauge designation is stated. Metal gauges are no longer referenced in ASTM Standards. It is still an industry practice to specify steel components by gauge. Because many of the designs contained herein refer to metal gauge the following information is to be used as a guide where field questions occur. The tables shown herein are to be used as a reference and the local Authority Having Jurisdiction shall be consulted if discrepancies exist between these tables and a local code requirement. Due to structural considerations and fire performance considerations the minimum thickness tables are different for steel deck (floor or roof), load bearing studs and non-load bearing studs.

The minimum thickness for load bearing steel studs is based upon ASTM C955-96, "Load-Bearing (Transverse and Axial) Steel Studs, Runners (Tracks) and Bracing or Bridging for Screw Application of Gypsum Panel Products and Metal Plaster Bases". The color code denoted by the ASTM Standard is also shown below. For load bearing steel studs, the minimum bare metal thickness shall be as follows:

For non-load bearing studs, the minimum thickness is based upon the gauge conversion table found in the 1997 Uniform Building Code. For non-load bearing steel studs, the minimum bare metal thickness shall be as follows.

For additional information on steel-framed wall and floor-ceiling assemblies, there is a searchable directory on the Steel Framing Alliance website, at www.steelframing.org. Also, for additional information on the details and limitations of these systems, go to the UL web information page on these assemblies:

Question: Can mold grow on steel studs?

Answer: That's a good question, and one that requires a little background for the answer.

Mold requires three things to grow:

Steel does not contain any organic material, and therefore cannot support mold growth. However, if someone or something has left a residue of organic material on the steel framing, there is a chance that given the right conditions, mold could grow.

As with any framing material, the best practice is to keep the steel studs dry. Even if they get wet during construction, or there is a one-time event such as a pipe bursting in a wall, there should be no long-term problem if the cavity is dried out properly. It is persistent wetting, such as a steady plumbing or roof leak, which causes the greatest risk of supporting mold. Even then, the mold will most likely grow on organic surfaces, such as the paper facing of the gypsum board or wood framing members, rather than steel. In steel framing, when everything is clean and dry, there will be no opportunity for the mold to grow.

Note that the Steel Framing Alliance has an excellent publication on this issue: listed under the - About Steel Framing - bar on the home page, go to -Issue Papers - for a free download of the issue paper on mold.

Question: Wouldn't enamel coated steel provide better rust protection for a steel frame home rather than galvanized steel.

Answer: Enamel painted steel without a galvanized coating below does not provide a better protection. The reason is that zinc, through its sacrificial galvanic action, can "heal" cuts, scratches, and abrasions in the steel. With the rough handling that construction products receive, as well as the cutting, drilling, shearing, and fastening of members, the coating gets cut and scraped away. The galvanized coating works better than the enamel at covering areas that are cut or scratched.

Some of the very best coatings for steel products are painted over galvanized. The automotive industry has come a long way over the past 20 years in providing better coatings, and this is what they use in several applications. If for some reason the paint is cut or scratched, the zinc below the paint can help provide protection, and reduce the chance of blistering where moisture gets below the paint surface and rust progresses.

Enamel over galvanized would be a very effective coating for steel framing. However, due to the cost, not many manufacturers make such a product. There are some specialty coil coaters that will paint material to be rolled into framing members. As part of the interior exposed drum wall in the Georgia Dome, studs were galvanized, painted, and then covered with a thin sheet of protective plastic before they were rolled into the "C" shape. As installers put the framing into place, they removed the plastic. After over 10 years of exposed, in-place service, these studs (which can be seen from the seating area and playing field) are still in excellent condition.

Please see "Corrosion protection for life."

       Definitions         Back to top

• AISI American Iron and Steel Institute
• ASCE American Society of Civil Engineers
• AWCI Association of the Wall and Ceiling Industry
• CASE Council of American Structural Engineers
• CCFSS Center for Cold-Formed Steel Structures
• COFS Committee on Framing Standards
• CFSEI Cold-Formed Steel Engineers Institute
• COS Committee on Specifications
• CSSBI Canadian Sheet Steel Building Institute
• LGSEA Light Gauge Steel Engineers Association, a Council of the Steel Framing Alliance - Today re-named CFSEI
• MBMA Metal Building Manufacturers Association
• MCA Metal Construction Association
• NAAMM National Association of Architectural Metal Manufacturers
• NAHB National Association of Home Builders
• NCSEA National Council of Structural Engineers Associations
• SFA Steel Framing Alliance
• SSMA Steel Stud Manufacturers Association
• STCA Steel truss and Component Association
• WTCA Wood Truss and Component Association