Railing on Metal Stud Parapet

[bookowski]

Can anyone recommend a detail for the following:

One story load bearing cold formed metal stud wall, roof will be accessible and needs a railing. The architect wants the metal stud to form a short curb/parapet (+/-12") with a railing mounted from the interior face of the short stud curb. See attached.

I was thinking of attaching a structural steel angle vertically to the joist below, the angle would be overlapped with the joist below the full joist depth (12"), essentially pushed down to the same top track on the wall below. I'm thinking that there is probably a better detail out there.

 

[bookowski]

Forgot sketch - attached.

 

[XR250]

I am more curious about the connection between the parapet and the roof. Looks pretty flimsy.

 

[a2mfk]

You are going down the right path using steel. Getting the 50plf/200lb lateral load for railings to work out is more challenging than most people think, especially if you are dealing with a light gage steel structure. Also agree with Excel, looks like one of those "magic" cantilevers, but maybe that is just the arch's sketch.

My question is why is the architect doing this? I would think this will look like crap, and why not just extend the parapet up to form a barrier?

 

[Jerehmy]

You're going to have issues with bolt pullout and compression buckling of the cold formed members at the connection of the railing post.

Make it a masonry parapet and this becomes 10x easier.

 

[bookowski]

I haven't checked the steel to CF connection yet but I was also expecting some problems there. I was thinking of adding some plate from the angle along the length of the CF joist to give me a bigger moment arm. Pretty ugly detail though. How would you do a masonry parapet on top of cold formed framing? I've never seen that.

a2 - re: extending the parapet up. When I've done this in the past it has been a curtain wall application where I run past the floor as one member to cantilever, or I've had diagonal kickers/braces back to the floor. Arch doesn't want braces. Can you develop parapet wind loads and/or railing loads by any attachment detail through just cold formed? I'm not too comfortable with CF, it seems very flimsy to me.

 

[ztengguy]

Cant just cantilever the studs up from below??

 

[Jerehmy]

yeah extending the parapet up to 3'-6" would be ideal. just make sure its braced properly with U channels and you should be fine. CF is flimsy when its not braced properly.

Then all you have to worry about is a good connection at the base.

 

[PUEngineer]

I've had to use a similar detail on concrete and steel framed buildings. I can share my experience as to why extending the studs up to handrail height isn't acceptable architecturally....shorter people (kids?) can't see through a metal stud parapet...not my words, just repeating.

I think continuous studs up and past the roof, to whatever dimension the arch is showing, is your best option. Then between those vertical studs, run two horizontal studs, parallel to your top track, one at each of the two anchor locations you have shown. No idea if the forces are manageable, just a thought.

 

[bookowski]

I agree that running the studs past the floor is best. A rookie question but how do you do this in load bearing metal stud? I've only seen platform framing, never balloon. Does the back face of joist frame flush to back side of stud?

 

[dhengr]

Bookowski:
I would balloon frame that top level up to the top of the parapet, and top that with a structural channel, toes down, and well fixed to every stud. This, so that at every handrail attachment you brought three or five studs into place w.r.t. the 50 and 200lb. railing loadings. At each post attachment you should reinforce that stud, and you should tie all the studs back into the fl. jsts. and fl. diaphragm. The detailing for load distribution, and against water penetration gets kinda fussy, but the Arch. wants what he/she wants and can pay for it to be done right, or adjust their wants.

You could put ledger beam (CF channel) on the inside of the studs to pick up the jsts., but the Arch. probably won’t like that even though his want forced this detail. You could line the studs up with the fl. jsts., so that the jst. rested against the back side of the stud web. Then put a seat angle under the jst. as well as attaching the jst. directly to the stud web. You might also need fire blocking at this level, which could be part of the jst. support system. Look through USP’s & Simpson’s catalogs for various hardware choices.