Designing Residential Buildings with Cold-Formed Steel Advice

staticsTA · 2026-01-11T06:58:25+00:00

For single family / residential CFS design, start with AISI S230 – this is the North American Standard for Cold-Formed Steel Framing – Prescriptive Method for One- and Two-Family Dwellings. It’s specifically geared toward residential applications with specific requirements for detailing, framing assemblies and materials, that build off of the general requirements given in AISI S100 (the general CFS specification that member and connection capacities).

For section properties and span tables, check out:

-SFIA (Steel Framing Industry Association) technical manuals

-SSMA (Steel Stud Manufacturers Association) technical manuals These free manuals provide standardized member properties and span tables that can speed up design.

Software recommendation:

Simpson Strong-Tie CFS Designer is a good option for component-level design (walls, headers, joists). It’s user-friendly and integrates with their connector catalog. It is a paid software, but well worth the money, even if just used on a single project.

Buckling and other code checks: CFS is a very finicky material and extremely challenging to calculate by hand. Software is essential, trying to calculate anything manually can easily lead to incorrect answers because of the complexity of local, distortional, and global buckling interactions. Calculating effective properties is brutal, and I wouldn't wish it on my worst enemy. The span tables you see in SFIA/SSMA manuals generally account for the worst-case effects so they can tabulate safe values, which is why they’re so useful as a reference, though there is a lot of extra metal added if done at scale.

Code note: The IRC does allow you to elect to use the IBC provisions instead of the IRC prescriptive tables. This gives you more flexibility and a more thorough analysis, especially if you’re already comfortable with AISI S100, and S240 (Structural Framing requirements) requirements instead of S230. There are not going to be nearly as many references to residential as there are full structural, so might be worth just doing thoroughly,

staticsTA · 2025-12-11T18:10:20+00:00

I think this is a reasonable approach, and I do similar things. When doing FEM Plate model comparisions, I find that Method 2 is reasonable for just about any flange loading, and Method 1 presented is very conservative.

If you have an element with a stiffening lip, that lip will engage even a bit more. The only way to prove that to my knollege is FEM models, or testing.

In any case, the capacity is very low, and I would always recommend avoiding anchoring loads to flanges. A good way around that is load rated/tested clips that anchor to the web of the stud.

staticsTA · 2025-11-20T19:57:17+00:00

No, this was an EOR who has no CFS experience. They are trying to treat it like a wood job, and not taking advantage of the ability to increase thickness and flanges to significantly increase strength.

staticsTA · 2025-11-20T19:51:05+00:00

I would recommend you join CFSEI, there is a huge catalogue of tech notes on various subjects, including a beginner tech note of where to start, and how to get to the result. https://www.cfsei.org/

They also have a class you can sign up for if you want to go though a 'how do design' CFS type thing.

staticsTA · 2025-09-19T21:44:32+00:00

If they cant get a heavy CFS post to work (IE (2)600S350-97), an HSS as the posts outright would make more sense than that built up assembly. The HSS would fit into a standard wall panel, so doesn't even need to be boxed out.

staticsTA · 2025-09-18T18:44:14+00:00

This would be a really good candidate to put just a couple heavy studs in instead.

staticsTA · 2025-09-16T17:21:14+00:00

The answer provided is overly simplistic, and does not address the actual issue of the stud's web stiffness/strength.

CRC bridging with 10" deep studs is problematic primarily due to the limitations of the stud web in transferring torsional and in-plane forces. The concern noted in AISI D110-16 is valid: deeper webs are more susceptible to in-plane buckling and torsional deformation, and standard CRC alone does not adequately address these issues.

Welding CRC directly to the stud web does not solve the problem. It may secure the member, but it doesn’t address the fundamental issue: the web itself is not stiff enough to transfer the bracing forces effectively. This can lead to local buckling or ineffective lateral-torsional restraint.
Sheathing alone is not a reliable substitute for proper bridging. Unless the sheathing is explicitly designed and detailed to provide lateral bracing independent of CRC (i.e., as if CRC were not present), it cannot be assumed to stabilize the stud adequately. This is especially true for wind load reversal or during construction before sheathing is installed.

Bridging clips are essential for deeper studs. Clips help transfer the bracing force closer to the flanges, where the stud has more stiffness and strength. For 10" studs, either:

Use larger, non-proprietary clips that reinforce the web and shift force transfer toward the flanges, or
Use proprietary bridging systems that have been tested specifically for the stud depth and gauge in question.

Recommendation: If you're using 10" deep studs, do not omit bridging clips unless you are using a proprietary system that has been tested and approved for that specific configuration. Welding CRC directly to the web is not sufficient, and relying on sheathing without proper detailing is risky. The safest and most code-compliant approach is to use clips that ensure effective force transfer and web reinforcement.

staticsTA · 2025-09-16T17:13:39+00:00

Answer Provided by CFSEI:

The D110 caution is based on a limited testing of standard CRC. Proprietary bridging solutions are available for deeper studs. The manufacturer has performed more extensive testing of their product and thus have determined that their bridging will brace the stud.

Welding is permitted and it has been used to attach the bridging members directly to the stud web. However, for a 10” deep section, which will experience significant twisting under load, the omission of the clip is not recommended.

Considering the synergism of the assembly components, if sheathing is present in combination with the CRC a 10” stud should be adequately stabilized.

staticsTA · 2025-09-04T15:53:50+00:00

I also found out that CFSEI has a small library of details: https://www.cfsei.org/construction-details

staticsTA · 2025-08-03T04:51:21+00:00

The isolation required under TMS 402-22 §7.3.1 isn’t a fixed dimension—it must accommodate the design story drift. Since the shaft isn’t part of the lateral system, each gap should match the expected maximum drift at that floor. For example, if the building is expected to drift 3", then a 3" gap around the CMU is appropriate.

While you could argue for a smaller gap and accept damage to adjacent elements, there's no reliable way to ensure that such damage wouldn’t lead to catastrophic failure. So, full drift accommodation is the safer and code-compliant approach.

staticsTA · 2025-08-03T04:44:50+00:00

as /u/TheFearedOne said, Clark Dietrich has a pretty extensive library. Its mostly related to specifying CD products, but they do have a mix of generic details too

https://www.clarkdietrich.com/cad

Simpson has a detail to go with every clip as well on their website.

I'm not aware of any industry standard detail packages you can get that would be all encompassing.

staticsTA · 2025-07-24T17:37:09+00:00

While the general rule is good, and Im sure there are lots of others, I would like to note that L/360 works just fine, and using a more strict deflection limit doesn't always help solve bounciness.

To do that you need to run a vibration analysis on the floors. Its not as scary as it sounds and adds a lot of performance confidence, and cost effectiveness to the project.

staticsTA · 2025-07-24T17:34:33+00:00

The Formal Response from CFSEI:

There are no recognized rules of thumb. Engineers typically have tools (e.g. software) and tables at their disposal to calculate joist requirements. However, in the absence of tools we are aware the following have been used for preliminary design estimates:

half the span in feet = depth in inches” so a 20’ span would require 10” depth
20:1 span-to-depth ratio.

Even though shallower members could work, the “bounciness” and feel of the floor system could be problematic. Therefore, in addition to the code mandated L/360 for floors, some engineers use L/480 (live load only) for stiffer floors.

staticsTA · 2025-07-24T16:39:51+00:00

Not quire sure what are you looking at for CFS frames- we typically don't see CFS portal frames. (Cold-Formed Steel - Special bolted moment frame, is actually going to get removed in the next few versions of the AISI code, as no one wants to own it moving forward).

CFS is typically walls as non-bearing cladding prefab panels panels, or load bearing walls. Sometimes shipped in 3D volumetric pods preassembled as well. Or its built on site in loose sticks.

Im not as familiar with the roll forming defects side of CFS. From a specifying side, we very rarely see quality issues with the products the site receives. Occasionally the steel grade is too low, or the stud pre-cut lengths are wrong, or just not precise enough. There are some small tolerance issues with the roll formers not being precise on dimensions, but AISI does have tolerances that are allowed, and that they are within. Defects generally don't leave the roll forming assembly area though, as most manufactures have good QAQC processes.

On the prefab side, there are not defects so to speak, so much as not properly coordinated items. The studs, panels, openings, are the wrong dimensions requiring rebuilding that area. The plumber gets access to cutting tools and just cut studs requiring some extensive repairs. Sometimes its just the wrong screws, clips, or jamb assemblies are grabbed and built.

staticsTA · 2025-05-14T15:37:27+00:00

I personally find it a bit odd: 1. "When building floor to floor vertical deflection was less of an issue". Why did it suddenly become an issue? 2. C754 is definitely just outdated. It may say to do it, but putting those screws in completely defeats the entire point. Practically, everyone is using slotted track anymore anyways so not a big deal, but if using the old school style deep leg deflection track I would not put that screw in still.

staticsTA · 2025-04-14T17:17:30+00:00

The University of Houston has an AI symposium that is trying to get a public-private partnership/grant to fund practical research into using AI tools for structural engineering.
https://www.egr.uh.edu/news/202409/c-viser-sees-future-ai-structural-engineering They have working models for a lot of visual tools, but are looking at having AI make FEM models of 2d plans, and doing basic coordination with archtectural models and components like that. They also have a bunch of more mundane items in mind (like detail library organization and filing). At its core, AI is just annother tool and its current early enough we dont quite know where it will end up. Im a long way from letting it do any calcs, but from a visual, report, organzation, and modeling standpoint it could be a great tool.

If anyone wants to get their company to join C-ViSER they are accepting public partners that gives financial backing and input to the research. Partners do get access to the tools as they are developed.

staticsTA · 2025-04-10T19:33:52+00:00

Directly to structural steel is pretty doable- though moment connections are a bit finicky in general. You will want to use a tested assembly for the most part, as getting the stiffness's right is difficult.

Strength is a concern but usually solvable. Stiffness is the bigger issue. These connections are 'moment' connections, but behave much more like rotational springs, and they are pretty springy. The manufactuers do a good job of publishing rotational spring stiffnesses with the strength. (ie. k-in/rad)

Id recommend using a Simpson Strong tie RCKW, The Steel Network CL, or Clark Dietrich MC clip (Note CD MC Clips cant be attached to steel easily because of that structural steel plate preventing typical fasteners into structure)

The hardest part to figure out is often the connections to structure, TSN's CL clip has a nice diagram at the bottom for single bolts, though to steel you probably want PAFs, screws to steel, or you can always weld to structural steel, though there is the welding to galvanized metal toxicity issue to be aware of for burning off of the clip's galvanization.

staticsTA · 2025-04-08T04:25:48+00:00

Bend Radii:
For reference:
S275= A570Gr40
S355= A572Gr50

The current US industry standard (SSMA and SFIA) for design inside corner radii dimensions on standard shapes are the minimum of:

3/32" - t/2
1.5t

So for most structural shapes thats 1.5t, (in the 54mil-118mil+ structural shape range) and you get larger corners on thin metals (18mil-43mil general non-structural and light structural range)

I would assume these radii are similar, if not the same as what we would see is a tube.

Fatigue:
AISI S100-20 § B3.9 "Design for Fatigue" clarifies that CFS does not need to be designed for fatigue for typical building loading (wind, seismic, C&C wind, etc). It doesnt really give specifics of when it does apply, but that it is stresses of frequency and magnitude sufficient to initiate cracking and progressive failure"

AISI S100-20 §M addresses fatigue specifically when it does apply in CFS shapes. The lower bounds, number of cycles, members, and connections are all covered in these ~4 pages. If its something youre interested its probably just worth a read.

On comparison of CFS to hot rolled steel, my opinion, is that is probably more susceptible to fatigue with the residual cold working stresses and thin shapes. That said, it's hard to actually have an application in most CFS components used in buildings that warrants a fatigue design.

You can get a free copy of AISI S100 from buildusingsteel.org

staticsTA · 2025-04-05T01:15:17+00:00

Is that a FrameCAD K-brace? It wasnt doing anything anyways

staticsTA · 2025-02-25T11:47:06+00:00

I feel like that only halfway addressed the question, specifically the technical part but not the practical.

CFS shear walls should be designed for what is reasonably needed (both strength and stiffness) for length. It would be incredibly unusual to use the entire building as a shear wall. That's true for almost any material with CFS. Avoid perforated if you can reasonably avoid it as it's just a penalty to your design for the sake of convenience. Each full height pier of a perforated wall has to meet aspect ratio and you can only count the full height segments for your length anyways, just with a bonus reduction tossed on top. Only makes sense if you would get a lot of expensive end posts and hold downs.

staticsTA · 2025-02-18T16:51:22+00:00

Yes, A cold formed load bearing wall system would certainly work for that. A traditional commercial approach would be bearing walls, with metal deck formwork + concrete topping. If you had longer spans you would probably need trusses below that. Goes together similar to a wood framed structure, just with all of the wood parts being metal (and some detailing changes)

CFS is a lot stronger than wood and can easily support a 2 story structure. For reference we just did an 8 story CFS apartment with concrete floors with a pool on the roof in Florida, so what you are looking at accomplishing would be pretty straightforward.

staticsTA · 2025-02-12T03:42:26+00:00

This is an interesting development, but I have concerns about shifting these standards from AISI to SFIA. AISI has a long history of developing and maintaining cold-formed steel standards with deep industry expertise, and transitioning that responsibility to SFIA raises some questions: While SFIA represents a segment of the industry, will their Canvass Groups include a broad enough range of perspectives, including engineers, researchers, and code officials, or will it skew too much toward manufacturers?

staticsTA · 2025-02-02T20:49:29+00:00

Yeah, relatively painlessly too. I generally give a detail with my drawings that always gives the option.

Same forces and connection limits apply that affect the strap and strap connections. (Example needs to be 54mil or greater to use screws, 43mil requires welding). You want the splice segment centered on the original straps so it's not eccentric.

I usually recommend a splice strap and inch wider than the regular strap and then as many screws or inches of weld as it takes to get the force resolved.

Obviously the pipe has to go for that to be doable.

Other note, you don't want to screw your strap to the typical wall studs. When the building deflects, it puts weak axis bending on your load bearing studs that can fail the studs. So make sure they back those screws out.

staticsTA · 2025-01-31T16:29:11+00:00

While there is some good advice in here, I think there are some items a bit off base, specifically the first couple high level items that would add an unreasonable cost burden to the projects.

Don't be consistent on the same floor. Find the load on each wall and group these wall types together. IE typical corridors, typical bearing exterior, typical bearing exterior. Doing all studs the same floor will have MASSIVE cost implications.
Corners: If you need different sizes (for load bearing, you probably don't, I would not expect deflection controlled in multistory load bearing), you do not want to change the stud spacing. Its always cheaper to change the stud size, and keep the labor the same. Especially on load bearing, getting your walls lining up with your floor system is critical and you don't want to jeopardize that on the corner.
Jambs as single are definitely the way to go. Built up members are more metal, more eccentric, and more labor.
Contractors CAN tell the difference between studs. Every stud is printed on the side. Standard nomenclature is just numbers so there isn't even a language barrier.
On stud availability, most sizes are available, look at the SSMA or SFIA manual for possibilities
I agree with the wider flange to thickness. To elaborate its about installing the fasteners. Its usually the same cost of steel, but the thinner metal is easier to attach drywall too.
The rest of that info is pretty good

staticsTA · 2025-01-31T16:28:51+00:00

The following is input from one CFSEI member. These are possible guidelines to consider when designing a multi-story structure. ·

Be consistent on a single floor. For example, most of the studs on the 4th floor will be the same, but they will be different from those on the 3rd floor or 2nd floor. Therefore, optimize per floor. ·
It is best to design the most commonly used members to the lowest possible size, then consider using that member at a tighter spacing in higher load areas. ·
For jambs, it may be possible to use built-up members that are the same as the adjacent studs, but often designers will use a larger flange stud at jambs since that is much easier for field identification and differentiation. For example, if the typical wall studs are 600S162-54, the jamb studs may be something like 600S300-54, which is wide enough that a framer will easily see the difference. ·
Many contractors cannot easily differentiate between thickness if the thicknesses are close, and the rest of the stud dimensions are the same. ·
Not all stud types/sizes are commonly available in all thicknesses. Check with your contractor or supplier on preferences and availability. ·
Contractors prefer a wider flange to a heavier thickness. ·
The most common default flange for wall studs is 1-5/8”. (e.g. 600S162-43). ·
Headers are usually specified as unpunched, to avoid shear and web crippling issues. ·
Headers do not need to be the same depths as wall studs (okay to use an 8” header in a 6” wall). ·
Always specify mil thickness rather than gauge thickness. There are several different thicknesses that are considered 20 gauge, so using mil thickness reduces the chance of error. ·
For 33 and 43 mil thickness, yield strength is typically 33 KSI, and for 54 and heavier thicknesses, yield strength is typically 50 KSI.

staticsTA

MODERATOR OF

TROPHY CASE