Viability of Cantilevered Cold Formed Stud Wall Framing For Use as Guard Rail 1

[KootK]

Gotta wee problem that needs sorting by the end of the day. It's a patio guardrail system. I'll probably build it out of intermittent HSS with CFM in between. However, I also need to vet the concept of possibly omitting the HSS and just cantilevering the stud work. I know that stud work can be cantilevered (wind sill etc) but I've never done it myself and I've always considered that to be a light load and low importance kind of system. So my specific questions are as follows:

1) Is cantilevered CFM stud at all viable for a guard application?

2) Anybody know of a design guide etc that covers this condition?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[XR250]

I have used these on cantilevered sills. Not sure how they will "feel" for a guardrail.

https://www.steelnetwork.com/Product/StiffClipCL

You could go thru the stiffness calc. they provide and maybe get a better sense of it.

 

[KootK]

That's just what I needed.

Guard Load + Wind = ~4500 lb-in per 6" stud @ 16" o/c. That's looking like a clip on every stud for a reasonable gauge. I'd have to think that HSS @ 6' or so with infill in between would have to be cheaper, right? That's a lot of hardware and anchoring.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[DaveAtkins]

Steel Network also makes a product for exactly your application: Link

DaveAtkins

 

[BridgeSmith]

Not sure of the section properties of the studs, but I would think the system would have to be strong enough for the typical railing load of 200 lb point load applied at 42" above patio surface. My guess is that the lateral strength and stiffness of the top rail cap would determine whether it will be adequate. In other words, is the top rail strong enough and stiff enough to engage the number of studs required to resist the 200 lb horizontal load? (I assume 200 lbs vertical shouldn't be a problem).

 

[jayrod12]

Simpson Strong-Tie has a clip as well for this application
RCKW - Rigid Cold Formed Kneewall connector

 

[T_Bat]

Not sure what, if anything, is below the patio or what the floor is constructed from - but if it's all new construction can you extend the wall studs below up to form the guard? I've used this for some LG mezzanines in the past. May not apply to your situation.

 

[Mjkkb2]

Never done it but used the stiff clip for cantilevered sill. As long as your deck is concrete you can make it work with the clip. I would agree that by the end of the day you'd be better off doing the HSS, not sure how long your deck is but a clip at each stud makes for a lot of labor to connect them.

 

[KootK]

Thanks for the detail T-Bat. Unfortunately, I'm all glass below. Main floor glazing fer miles.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[MikeHalloran]

A former employer had a set of interior restrooms refurbished over a weekend; concrete block outside walls, CF steel interior walls and ceiling. It took an extra two days, because the contractor had brought self-piercing pointed screws, which work very well in the 'light' framing, which I'd estimate at no more than #26 ga thick. His supplier had delivered all the framing in #16 ga, at no extra cost, so he had to predrill every screw, since he had not brought self-drilling screws.

You can jam an icepick or a pocketknife right through the 'light' stuff; I wouldn't trust it for what you're considering.

I don't know how many gages are stocked, but I suggest you clearly specify which one you are designing for.



Mike Halloran
Pembroke Pines, FL, USA

 

[dhengr]

KootK:
One of the biggest problems will be finding places and details and then coordinating that with the stud spacing, so that you can make that cantilever moment connection adequately. That’s not appreciably different than the post connection deficiencies we see on wooden decks. Then, you have the problem of flashing and waterproofing that wall detail at the floor level. The connection hardware others have shown looks like it should work, except for cost and labor. And, T Bat’s detail where you can side lap stud and joist webs and come up with a screwed moment connection looks pretty good.

 

[KootK]

I appreciate all of the responses but I've got what I came for on this one. HSS posts with stud wall infill it is.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Ron]

KootK.....waterproof the hell out of it! All prone to cavity corrosion!

 

[XR250]

I'd have to think that HSS @ 6' or so with infill in between would have to be cheaper, right? That's a lot of hardware and anchoring.

You would think but for some reasons GC's around here say the red iron guys charge waaay more than the light gage quys so they always push for light gage everything.
I have found the anchoring is always the issue in these situations as there never seems to be enough edge distance.

 

[dik]

Further to Ron's comment, any insulation should wrap completely around the upstand and be contiguous with the roof insulation.

Dik

 

[Brad805]

I have found the same as XR. Having it under the GC makes for one less item to coordinate. That said, if there is already a lot of misc steel, your method is a good idea.

 

[KootK]

There is a lot of miscellaneous steel on this one. Precast 2nd floor deck with everything and anything hanging from it. The infill is actually likely to be wood. And that's find by me as I actually prefer that from a durability perspective. With a 2-2x6 sill plate, I've found that I can open up the spacing t 10' o/c posts. Not too shabby.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.