General Cold-Formed Steel Framing FAQs

 

What standards govern the manufacture and physical requirements of cold-formed steel products?

View ClarkDietich's Material Certification Page for more information on code approvals and performance standards.

What is an Equivalent (EQ) Drywall Stud?

Gauge equivalent drywall framing must meet the minimum performance requirements of conventional drywall framing. ASTM and AISI define conventional drywall framing studs as basic C-shaped members. These basic members do not take advantage of today's roll-forming and steel making technologies that enhance the shape and strength with greater efficiency. ProSTUD employs these technologies and exceeds the performance of conventional drywall framing.

Visit ProSTUD's "What is an EQ Drywall Stud" web page for more information.

For interior framing, what is the difference between composite and non-composite limiting heights tables?

Composite limiting height data can be applied to walls where gypsum board is installed on both flanges of the stud for the full height of the wall. Non-composite conditions are common in all structures. When the gypsum board stops at the ceiling level, but the stud continues to the deck, it is a non-composite condition.

Visit our ProSTUD Drywall Framing Limiting Heights Tables web site to determine which limiting heights table you should use.

When is it required to use lateral bracing on an interior wall?

Typically lateral bracing is required in a non-composite condition (described in the question above), above the location of where the gypsum board stops, or in a wall where gypsum board is placed only on one side.

Visit our ProSTUD Drywall Framing Limiting Heights Tables web site and click on the non-composite section for more information.

What are the bracing requirements for curtain wall framing?

Curtain wall framing is braced by the normal attachment of wall facing materials to both sides of the studs. However, the use of wall facing materials for bracing should be given consideration during construction. Normally, sheathing is applied to the exterior of the studs, but the inside flanges are left unbraced until the interior is finished. Prior to the installation of interior board, high winds can cause stud damage due to the lack of interior bracing.

Steel strapping, installed horizontally on the interior flanges at a maximum of six (6) feet on center, in conjunction with the sheathing, will brace and protect the stud framing during construction. If mechanical bracing is required, it can be either steel strapping run horizontally on both sides of the studs and attached to each flange, or cold-rolled channel run horizontally through the stud punchouts and attached to each stud web. The maximum spacing for mechanical bracing of curtain wall framing is six (6) feet on center.

See our lateral bracing details in our CAD Framing Details for more information.

What are the bracing requirements for combined (axial and transverse) loaded studs?

Wall framing with combined loading is subject to vertical loads during construction, and prior to being fully braced by the wall facing materials. To ensure the framing is adequately braced during construction, mechanical bracing is required to be installed concurrently with the framing. Mechanical bracing can be either steel strapping or CRC (Cold-Rolled Channel) run horizontally through the stud punchouts and attached to each stud web. The maximum spacing for mechanical bracing of steel framing with combined loading is four (4) feet on center.

See our lateral bracing details in our CAD Framing Details for more information.

What are the bracing requirements for floor joists?

The top flange of floor joists shall be laterally braced by the application of floor sheathing fastened to the joists. The diaphragm effect of the floor must be judged to be structurally adequate for the lateral bracing of the top flange. In addition, joist bridging should start and end with two (2) spaces of solid bridging. Between the start and end spaces, a repetitive pattern of five (5) spaces of strapping, on the laterally unbraced flange, followed by one space of solid bridging can be used. Joist bridging should be placed as follows:

Span Bridging Required
< 14 ft           one row at mid-point
14 to 20 ft   two rows at third points
over 20 ft    one row every 6 ft

See our lateral bracing details in our CAD Framing Details for more information.

What fire/sound rating can be achieved while providing cold-formed steel framing in wall, floor or ceiling assemblies?

Since the steel stud or floor joist is one part of a wall or floor/ceiling system, actual wall and floor assemblies are tested for their fire resistance while maintaining their structural integrity by various approved testing agencies throughout the country.

For interior framing reference ProSTUD's UL & STC Ratings web site.
See our Fire & Acoustic Support Docs web page for other resources.

In an engineering sense, when is 50ksi material required in lieu of 33ksi material?

The 33ksi or 50ksi refers to the "grade of steel" or its yield point. This is a material property for strength, not for stiffness or resistance to deflection. Generally speaking, 50ksi material tends to be more likely required in high-load applications (heavy floors, heavily loaded load-bearing studs, load-bearing headers). 50ksi is rarely required in curtain wall applications. Some markets or specifications require 50ksi for material 16 gauge and above. 33ksi steel will be specified unless the customer indicates 50ksi at time of the order.

What allowable deflection should be specified for curtain wall applications?

The main purpose of specifying an allowable stud deflection for curtain wall framing is actually for determining what is an acceptable deflection for the wall facing materials. A metal stud is ductile and therefore can perform at a wide range of deflections. Wall facing materials tend to be more brittle (Brick, Stucco or EIFS), and thus have a more stringent maximum allowable deflection. The project architect or project specifications should note what the allowable deflection is for a given wall facing material.

For more information on curtain wall framing, view our Curtain Wall Sizing Sheet.

What floor live load should I use for a joist application?

The nation's model building Codes, IBC and IRC have minimum required floor live loads (PSF). The Codes, for example, use a 40 PSF floor live load for residential, 50 PSF floor live load for offices and a 125 PSF floor live load for light storage.
View our floor joist sizing sheet for common live and dead loads. Since these are minimum required loads, higher loads may be required for a specific project.

If stamped shop drawings are required for the project, how much time is required to get a full engineering package with a state stamp?

Lead times for engineering consultants typically range from 2-6 weeks depending on the complexity of the project. In addition, after our ClarkDietrich Engineering Service Team receives the contract documents (architectural drawings, structural drawings and owner's specification), a proposal or contract (which includes cost and schedule) is prepared by the design team. Using 4 weeks as an average backlog, it is best for the customer to allow for 5 weeks of preparation for a final stamped engineering package.

Contact ClarkDietrich Engineering Services at (877) 832-3206 for obtaining stamped engineering packages.

What determines whether or not punched versus unpunched webs should be provided?

Wall framing members need punched webs to accomodate plumbing and electrical lines. However, heavier loaded members such as floor joists and headers are not as likely as wall framing members to require punched webs; therefore, they may conservatively be ordered with unpunched webs. When a heavily loaded framing member has a web punch located at or near a bearing support, it is advised to bring this condition to the attention of the project engineer, in order for him/her to check the web's strength at this location.

I am building a steel joist/load-bearing wall system. Do the joists need to be in line with the load-bearing studs below?

The short answer is YES. Typically, the top track will not have sufficient bending strength to allow offset joists. However, if the joists will be offset from the load-bearing studs below, a structurally adequate distribution member needs to be provided between the joists above, and the load-bearing studs below. It is advised to have the project engineer specify the distribution member system.

Are screw connections required by the industry instead of welded connections?

The AISI Specification for the Design of Cold-Formed Steel Structural Members includes design guidelines for BOTH screw and welded connections. In other words, both methods, generally speaking, are equally acceptable. What usually determines screw versus welded connections are project specific conditions or the contractor's preference for means of fastening.

For screw values into ProSTUD Drywall Framing, click here

What are the basic functions of the AISI and ASTM organizations and standards as they apply to the cold-formed / light gauge steel framing industry?

The American Iron and Steel Institute (AISI) publishes the Specification for the Design of Cold-Formed Steel Structural Members. This Specification provides engineers and software developers the various formula for the load carrying capacity of cold-formed steel framing members. The American Society for Testing and Materials (ASTM) provides the minimum and consistent requirements for the material properties used in cold-formed steel framing. In addition, ASTM provides basic guidelines or requirements for the installation of cold-formed steel framing members.

What protective coatings are acceptable for cold-formed / light gauge steel framing in the United States?

ASTM A1003 Table 1 includes the universe of acceptable protective coatings permitted for light gauge steel framing members.

Is it required that stud and track framing members be marked?

Yes, the webs are to be marked at 48" O.C. spacing. ASTM C645 Section 14 identifies the requirements for drywall framing members. Likewise, ASTM C955 Section 12 identifies the requirements for structural framing members.

I am an architect writing my own master specification. Any advice for how to determine what potential stud manufacturers are acceptable?

It is strongly recommended to only include SFIA [Steel Framing Industry Association] or SSMA [Steel Stud Manufacturers Association] member companies especially since they are compelled to follow any applicable product or industry requirements determined to be mandatory by each association. In addition, ClarkDietrich, an SFIA member company, is also an active participant with other very important industry organizations such as ASTM and AISI.

View our Architectural Specifications or Architectural Spec Review Service sites for more information.