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Tile and Stone Applications on Equivalent Gauge (EQ) Steel Framing For Informational Purposes Only

Though relatively new to the U.S. market in comparison to conventional flat steel studs, Equivalent Gauge (EQ) studs account for nearly 90 percent of drywall studs manufactured today and have largely displaced conventional nonstructural steel framing mem bers in distribution. Ranging from a base metal thickness of 0.019 in. to 0.024 in. (0.5 mm to 0.6 mm), EQ Studs are lighter and thinner than the 20 gauge drywall (0.030 in [0.77 mm]) and 20 gauge structural (0.032 in. [0.84 mm]) studs that traditionally have been used behind tile and stone installations, but in some cases may still meet the demanding requirements of these systems. WHAT IS AN EQ STUD? ASTM C645, the code-referenced standard governing nonstructural steel framing members, sets a minimum base metal thick ness of 0.0179 in. (0.77 mm) (4.3). However, section 9.2 of the standard also allows the use of studs fabricated with thinner materials if it meets the performance requirements in the ASTM standard for nonbearing interior walls with gypsum panels (AC86) and conforms to the limiting height tables in ASTM C754. In order for a stud that is thinner than the proscribed C645 minimum to be allowed it must have a bending moment – or point where the stud buckles – that is equivalent or greater than its traditional counterpart. Manufacturers must provide sufficient data to enable calculation of design performance. Equivalent Gauge (EQ) studs utilize a combination of manufacturing technology and steel chemistry to achieve these neces sary results: • Reinforcing ribs are added to the web and flange of the studs to increase the stiffness. • High strength steel, typically twice the minimum of 33 ksi (230 MPa), delivers higher tensile strength at a lower weight. Industry association code compliance certification programs, such as that managed by the Steel Framing Industry associa tion, also impose additional requirements on EQ stud manufacturers. For example, all SFIA certified products must have: • Published composite limiting heights tables in accordance with ICC-ES AC86-10 • Published screw data (shear and pullout) and must pass the screw spin out performance test in ASTM C645 • Must meet the corrosion protection requirements of ASTM C645. Current TCNA Handbook methods state that tile and stone must be installed over conventional 20 gauge structural (0.0329 in. [0.84 mm] metal thickness) metal studs. In addition, 20 gauge drywall studs (0.030 in. [0.77 mm] metal thickness) studs were frequently used in place of the structural studs because of availability and potentially lack of knowledge by the installer. Both studs have performed satisfactorily over the years. As an alternate path, a simple performance standard can also be used by the design professional and framing contractor to achieve the same result. Provisions include: 1. The wall framing should meet a deflection limit of L/360 for the rated load based on the properties of the stud alone. 2. The wall studs must be adequately braced by cladding or lateral bridging to resist the applied loads and meet the applicable code(s). 3. The framing members must have a G60 or equivalent coating. 4. The framing members must pass all the fastener requirements (spinout and pullout strength) of the applicable wall stud standard. 5. Use of appropriate equipment with proper type and placement of fastener. RECOMMENDATIONS FOR THE TILE CONTRACTOR: It is the responsibility of the design professional and framing contractor to ensure that wall assemblies for tile and stone finishes are designed and assembled to meet performance requirements, and all manufacturers of EQ studs will have the technical data needed for design and confirmation of performance requirements. Although EQ studs are relatively new to the U.S., one or both of these techniques have been used for decades to manufacture cold-formed steel framing in countries around the world.

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NTCA Reference Manual | 2024 / 2025

Chapter 2 | Substrates