Cold Formed Track Acting as a Ledger

MJC6125 · Aug 19, 2022

In the past I have typically detailed load bearing CFS joists to be attached to CFS studs either through a platform framed bearing connection or by running the joists into the wall cavity and screwing them directly to the side of the wall studs. I have used a track attached to the wall studs like a ledger sometimes, but I have always introduced some additional clip angles to fasten the webs of the joists to the webs of the ledger track. I assume this is still required sometimes based on loading. However, I'm wondering if people omit the clip angle all together sometimes and just rely on the joist to track to wall stud connection similar to how out of plane wind loads are transferred out of wall studs at bottom and top tracks. See image below for reference. Do people try to get these ledger track conditions to work for floor and roof framing with no clip angles?

The reason it seems weird to me is because with wood framing, I always introduce joist hangers at ledgers, but never worry too much about a joist hanger or connector at the top and bottom of wall studs. I was thinking cold formed might be something similar. Do a connector piece for joists, but for wall studs the track connection and those screws are typically sufficient. However, if I input the CFS joists as a wall stud design in the Simpson CFS Designer software, and input the full gravity loads. I'm finding that a track connection seems to work for quite a bit of load. See additional image below. Is there anything I'm missing that makes the design of this detail different for a joist vs a wall stud?

dhengr · Aug 19, 2022

MJC6125:
A good part of the difference should be in the way the two members are normally loaded. The wall stud is normally presses down/up into the tract, screwed in place, and predominantly loaded in compression. While the normal loading of the joist in bending (simple end rotation), and any lateral loading tend to twist the joist out of the track. Thus, the tracks and screws have to deal with these additional loads, over and above the gravity load shear. Then also, the max. wind load (the shear) on a stud is only about 1/3 of the 45 or 50lbs./sqft. on the joist. Finally, the track doesn’t give you much of a bearing length for the joist reaction, and it has very little bending strength in its flange to accept this reaction. Also, remember that many deficient details, in any material, do seem to work in the short term, because they have never seen the max. loads or worst movement (rotation, twisting, etc.) conditions. Look up Dr. Roger LaBoube, P.E., Univ. of Missouri-Rolla, he’s spent his whole life in Cold-Formed Steel and is very knowledgeable; Cold-Formed Steel Structures, by Wei-Wen Yu is a good textbook; and all of the Codes, Commentaries, etc. by AISI.

XR250 · Aug 20, 2022

Also, any out-of-plane load on the studs needs to be resisted not only by your connection, but also by bending of the stud flange - which is not ideal.

MJC6125 · Aug 22, 2022

Thank you for the responses and references. I see the issues your raise.

Also, I did think a little about the bending of the stud flange for leeward wind pressures on the wall. I could see that possibly controlling the design to where a clip would actually be required to the side of the stud, opposite of the way I drew it going to the joist.

Do you have a preferred detail when dealing with CFS rafter/joist framing and CFS walls with a parapet. Do you?:
A. Platform frame, and figure out bracing of your parapet stud some other way.
B. Balloon frame, joists run into the wall cavity and screw to the side of the studs.
C. Balloon frame with a track ledger, doing clips to the joists and the studs?
D. Something else?

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Cold Formed Track Acting as a Ledger

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