Structural cold-form / light-gauge studs are used in axial load-bearing walls, curtain walls, interior partitions, floor joists, and roof trusses. Steel is required for most commercial and industrial buildings, and depending on code regulations, residential buildings can also require steel.
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Sizes and Metal Thicknesses
- Web sizes are: 3-1/2” (350S), 3-5/8” (362S), 4” (400S), 5-1/2” (550S), 6” (600S), 8” (800S), 10” (1000S), 12” (1200S), 14” (1400S)
- Flange stud sizes are: 1-5/8”, 2”, 2-1/2”
- Metal thickness for structural application: 97 mils *one thousandth of an inch (12 gauge) the thickest, 68 mils (14 gauge), 54 mils (16 gauge), 43 mils (18 gauge), and 33 mils (20 ga).
- Coating: All US Frame Factory Steel is coated with zinc and either has a coating weight of G90 or G60. This means the zinc coating is 0.90 oz/sqft or 0.60 oz/sqft respectively. For interior, non-load bearing, drywall studs, we use G40 coating or an equivalent Galvanneal coating.
Interior Steel Stud Walls: Sizing
To determine the load-bearing capacity, you’ll need to know the weight of the wall itself, any additional finishes (e.g. drywall, plaster), and any other loads (e.g. shelves, cabinetry). This will help you determine the minimum required size and thickness of the structural studs. According to the International Building Code, interior (non-load bearing) walls must be built to handle an interior pressure lateral load of at least 5 psf perpendicular to the wall. For walls spanning many floors with several exterior openings, loads of 7.5psf to 10psf are used. ClarkDietrich has a helpful table. Their most useful tool is the structural stud look up which will tell you what stud to use for your desired wall height and thickness. Note, the most common stud flange is 1-5/8″.
Exterior Curtain Walls: Sizing
Exterior curtain walls are made of structural studs in commercial or industrial projects. Their purpose is to support exterior cladding such as brick, glass, and stucco. When trying to decide on sizing, the key factors think about are:
- Local building code requirements for size and strength
- Wind Loads (this will involve performing wind load calculations to determine the size and strength of the wall required to resist the wind loads)
- Thermal performance and desired insulation levels
- Structural support required to hold the wall in place.
- The weight of exterior cladding
SteelNetwork has a nice page of framing tables (starting on page 17). I recommend using their tables when sizing Curtain Walls (see photo below).
Floor Joist: Sizing
The International Building Code (IBC) and American Iron and Steel Institute (AISI) provide guidelines for which metal stud floor joists to use and how to space them out. They recommend a maximum spacing of 24 inches on center for metal studs. BMP-Group has a useful table for floor joist sizing. We made an estimating tool that takes your joist spacing and room dimensions and calculates the proper floor joists lengths.
Metal Stud Screws: Sizing
AISI S100-12 North American Specification for the Design of Cold-Formed Steel governs the screw capacity utilized in structural elements. Important factors are the number of screws and pullover values. We’ve only used single #12 screws for each joint or double #10 screws in builds.
Structural Metal Header Sizing
The American Iron and Steel Institute did a great deep dive into box beam design and web stiffeners. There are two types of headers: L headers and Box Headers. They discuss the advantages of each starting on page 32.
The Canadian Sheet Steel Building Institute provides a full sizing table starting on page 79.
Stud bracing is applied for exterior Curtain walls and interior walls frequently adding a lot of sheer strength. This can add a lot of strength without increasing the gauge of studs. Metal Studs can be braced 3 ways.
- Center stud clips with a strap going though the center punch holes
- 2″ metal strap run on the wall face screwed into the flanges of each stud
- Flat strapping on the face of the wall in an X layout.
- For exterior Curtain wall design the is created by Sampson Strong-tie in their page about stud bracing for exterior curtain walls. Half way into the article you can see their sizing table for their center clip stud brace.
- This is a table studs with framing based on 12″ O.C, 16″ O.C, 24″ O.C for interior walls.
Center channel bracing thought hole punches
Flat strap bracing
This small job that has elements discusses, different gauge studs, some 6″ walls. The trusses are structural 20 gauge (362S162-33), the exterior curtain load baring walls are 18 gauge(350S162-43), the headers are made of 6″ 16 gauge (600S162-52) and 350T162-54 track. There is also stud bracing made of 2″ 18 gauge stud bracing. We also have X bracing made of 7.5″ 18 gauge flat strapping. See the 3D Matterport below. These are the structural drawings for this particular house.
CAD and programs for design
CFS-Designer (Cold-Form Steel Desginer) is a program created by Sampson Strong-tie that is basically computerized data base of span charts. You can download a free trail and experiment with a variety of different loads and spans.
US Frame Factory
Thank for checking out our article. We are a small scale roll-form operation in South Louisiana. The whole purpose of this page is simply to share resources we found with builders.