Residential Roof Opening Header Connection 3

[waytsh]

Hoping you residential regulars can give me some guidance on this one. Builder is adding a large dormer to an existing roof. He will be cutting four rafters to create a 10' wide opening. The rafters are on a 12:12 slope and headed off with three plies of 2x8's. I am looking for the best way to orient the header and design the connection to the supporting rafters which are also (3)-2x8's. Please refer to the attached drawing for reference. As far as I can tell, Simpson does not make a hanger that will fit this condition and be able to handle a load both vertically and laterally. Thoughts?

 

[kmart30]

Looks like a couple A35's will do the trick but I dont know what your loading calls for....

 

[JAE]

Could you use two A35's on each side. Simpson shows capacity in two directions.
For the lateral force F2, you can only use it if the load is toward the clip while the far side clip, being pulled, wouldn't participate.

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[kmart30]

hey JAE....I beat you to it!

 

[JAE]

Well done!!!

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[waytsh]

Thanks guys! You were both quick on the draw. The load demand in the F1 direction would be 270 pounds and in the F2 direction would be 1,240 pounds. If I rotate the header 45 degrees.

 

[Nor Cal SE]

Based on the 1240-lb load, it seems the A35's won't have the capacity in the F2 direction, nor is it likely that any other similar off-the-shelf Simpson clip pair with similar form and shape. It might be worth specifying a custom 1/8" or 3/16" angle each side with a couple thru bolts.

 

[CANPRO]

Keep in mind that you have sheathing and probably some strapping on the underside of your header to help with the F2 force.

 

[dhengr]

Waytsh:
Orient the top header to match the framing plane of the roof rafters, etc., not standing vert. with a ripped/sloped top, and other difficult framing cutting.. Then, to take care of your F2 loading, why not frame the opening with a trimmer rafter, much like you would frame a large window or sliding door opening with a trimmer stud to pick up the headers. Trimmer studs are variously called shoulder studs, jack studs, cripples, and other names, and they fit up under the header along side a full length (king) stud. Jack rafter is probably not appropriate here, they are a completely different animal.

 

[waytsh]

dhengr, understood about the orientation of the header. I will align so all the rafter cuts will be square cuts. As for the trimmer rafter you mention I am not sure I follow. We will be creating an opening through the roof so the dormer can be accessed from the bonus room in the attic area.Here is a screen shot of my RISA model to show what I am planning.

Where would these trimmer rafters be placed without restricting the opening?

 

[jayrod12]

I believe dhengr meant this

 

[waytsh]

Nor Cal SE, if I would go this route would I just run through the checks for the failure mechanisms specified in the NDS chapter on Dowel-Type Fasteners? Is there another reference for designing this type of connection. Thanks.

 

[waytsh]

Ah yes, jayrod12, that makes sense, thanks for the clarification.

 

[Nor Cal SE]

Waytsh, yes, that is what I was thinking. However, others have since listed some good options that might be better than my own.

 

[waytsh]

I did end up using the trimmer rafter in combination with the A35 clips. Great suggestions by all. Thank you for the help!