2x12 Ledger Supported by 2x6 Studs 1

[BSVBD]

Please see attached...

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1487186758/tips/Ledger_on_Stud_aqwuni.pdf[/url]

I've always hated this detail of supporting joists on a continuous ledger supported by lag screws in the narrow face of studs.

The numbers all work according to NDS (National Design Spec for Wood)... BUT, I've always been uncomfortable with it. I fight it every time.

Any alternate suggestions?

Thank you!

 

[jayrod12]

Notch the ledger into the studs? do you need the full 2x6 depth for the parapet bending?

 

[KootK]

I used to get pressured to do this all the time back in WI. Whenever possible, I steel it towards platformed framing and some means of stabilizing the parapet. In addition to the lag bolting issue, getting the diaphragm shear out to the exterior sheathing is an issue too. You either ignore it, install a ton of blocking, or go up and over the parapet. All icky.

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 hate this detail as well. I usually add a Simpson H10 to the stud and nail it into the roof deck or top of the joist to resist the pullout. Can also use an LTS12 if you lay it out right.
Also, you need to block between the studs to get the roof diaphragm shear to the outside face of the wall. (ugh - just saw Kootk said that already)
Simpson has some thin screws that have design values for the skinny face of a stud. Seems like a bad idea to put a 3/8" lag in the narrow portion of a stud - even with pre-drilling.

 

[calvinandhobbes10]

Have you ever actually seen it built this way, as bypass studs?

Double top plates and another parapet stud wall is how I've seen it built repeatedly, and what I go with. Agree with the issues about parapet stabilizing and diaphragm transfer, but I'd much rather give a direct-bearing load path for the permanent, sustained gravity load carried by the joists and then do some hoop-jumping to deal with the temporary wind loads.

 

[dik]

Bad detail... KootK and diaphragm loading pretty much says it all. Should ask the designer how he is going to achieve this...

Dik

 

[dhengr]

BSVBD:
I’d be really tempted to let the 2x12 ledger into the 2x6 studs by 1.5" (balloon framing style) to gain ledger bearing on the stud. You can’t expect full cap’y. out of 5-3/8" lag screws, 2" apart, and loaded parallel to the grain, in the narrow edge of a 2x stud grade stud. The stud will likely split lengthwise. Then, I’d be tempted to lower the 2x12 ledger so the LVL’s or TJI’s can bear atop the ledger and pass along side the studs. Provide web blocking on the TJI’s so you can nail their webs to the studs. Maybe consider strapping the top chord on the TJI’s to the studs with some hardware, watch top chord end spliting. On the other side of each 2x6 stud, I’d scab a 8 or 10' long (vert.) 2x4 stud, better than stud grade, from the double top pls. on the parapet on down, to start to take care of the parapet loads, and protect the main stud at that nasty notch and the max. bending condition. Then, you need some attention to careful spacing coordination and possible some special detailing around TJI’s and corner stud framing at each end of the bldg.

 

[BSVBD]

THANK YOU all for your replies.

Together, you've helped me convince my supervisor and the General Contractor to provide full-height, by-pass, parapet studs and shoulder studs to support the TJI and LVL joists. In addition, I will provide blocking between all joists and adjacent parapet studs to stabilize the joist ends at bearing.

I feel MUCH better!

Thank you!

 

[sandman21]

A let-in ledger is by far the worst way to support joist, just climb in the roof and see all the splitting. I would not use lag screws, if you want to use screws use Simpson SDS, personal use 16d to attached the ledger to studs. You need blocking to transfer the load to the plywood, which is the same blocking you would need to add if you platform framed them, no real additional work.