CFS Wall Stud — Cold-Formed Steel Stud Design

Cold-formed steel wall stud design per AISI S100. Combined axial load and bending, local and global buckling capacity for Cee stud sections. Educational use only.

This page documents the scope, inputs, outputs, and computational approach of the CFS Wall Stud tool on steelcalculator.app. The interactive calculator runs in your browser; this documentation ensures the page is useful even without JavaScript.

What this tool is for

Checking combined axial and bending capacity of CFS Cee-section wall studs per AISI S100.
Evaluating local, distortional, and global buckling under combined loading.
Comparing stud sizes, spacing, and bracing configurations for load-bearing walls.

What this tool is not for

It does not design the track, bridging, bracing, or sheathing attachment.
It does not handle CFS studs with punched web openings (punchouts) in full generality.
It does not check fire rating, acoustic performance, or thermal bridging.

Key concepts this page covers

combined axial compression and bending interaction (AISI S100 Section C5)
effective section properties under combined loading
flexural, torsional, and flexural-torsional buckling modes
bracing requirements for CFS wall studs

Inputs and outputs

Typical inputs: stud section (web depth, flange width, lip length, thickness), stud height, stud spacing, applied axial load (from header/roof), lateral load (wind pressure), bracing spacing, and steel yield strength Fy.

Typical outputs: axial capacity Pn, bending capacity Mn, interaction ratio (P/Pn + M/Mn), controlling buckling mode, and whether the stud passes or fails.

Computation approach

The calculator computes the nominal axial capacity using the AISI S100 Direct Strength Method, evaluating local, distortional, and global buckling for the Cee section under uniform compression. The nominal bending capacity is similarly computed for the section under bending about the strong axis. The combined interaction is checked per AISI S100 Section C5.2 using the linear interaction equation. Bracing is assumed to prevent weak-axis buckling between bracing points.

Frequently Asked Questions

What stud sizes are commonly used for load-bearing CFS walls? Common CFS stud sizes for load-bearing walls include 350S162 (3.5-inch web), 400S162 (4-inch web), and 600S162 (6-inch web) in gages 16 through 12 (54 mil through 97 mil thickness). The choice depends on wall height, axial load, and lateral load. For typical 8-10 foot walls in low-rise construction, 600S162-54 studs at 16 inches on center are common. Taller walls or heavier loads require deeper sections, thicker gages, or closer spacing.

How does bridging affect CFS stud capacity? Bridging (horizontal straps or channels connecting studs) prevents weak-axis buckling and torsional buckling, which are the critical failure modes for CFS Cee sections. Without bridging, the unbraced length equals the full stud height, and flexural-torsional buckling typically controls at a capacity much lower than the local or distortional buckling capacity. With bridging at mid-height, the unbraced length is halved and the global buckling capacity roughly quadruples (since buckling load is proportional to 1/L^2).

What is the difference between structural studs and non-structural studs? Structural (load-bearing) studs carry axial loads from above and must be designed per AISI S100 for combined axial and bending under wind or seismic loads. Non-structural (curtain wall) studs carry only lateral loads (wind) and their own weight; they are designed for bending only and can use lighter sections. The distinction affects the member capacity, connection requirements, and the applicable design standard provisions.

Disclaimer (educational use only)

This page is provided for general technical information and educational use only. It does not constitute professional engineering advice, a design service, or a substitute for an independent review by a qualified structural engineer. Any calculations, outputs, examples, and workflows discussed here are simplified descriptions intended to support understanding and preliminary estimation.

All real-world structural design depends on project-specific factors (loads, combinations, stability, detailing, fabrication, erection, tolerances, site conditions, and the governing standard and project specification). You are responsible for verifying inputs, validating results with an independent method, checking constructability and code compliance, and obtaining professional sign-off where required.

The site operator provides the content "as is" and "as available" without warranties of any kind. To the maximum extent permitted by law, the operator disclaims liability for any loss or damage arising from the use of, or reliance on, this page or any linked tools.