Author Topic: PFH: Dropped Header vs. Raised Header  (Read 4644 times)

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Offline Medeek

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PFH: Dropped Header vs. Raised Header
« on: March 15, 2014, 12:14:24 PM »
My questions with portal frames, nailing patterns and IRC vs. engineered shear wall design led me to an engineering forum that has been dissecting my previous PFH design.  However, the interesting thing is that there has been little consensus among the engineers on the "correct" way to frame these three garage doors.  I've discovered that many structural engineers are not very familiar with the IRC in general and many of them also dislike the portal frame method as shown in the IRC. 

So to get a different perspective on the problem I thought I might post the following two options in this forum as well to see what the builder community has to say on the matter.

I've done my best to design these two options so that they are in line with the IRC2012 braced wall provisions.  I have not shown all the details but just the general layout of the framing on the foundation.

Option 1 has three portal frames: one double portal frame, two single portal frames with a pony wall framed on top of each (dropped header).

Option 2 is very similar however it has the main LVL headers pushed up to the bottom of the double top plate and then a smaller header at the bottom of the filled in framing for the garage doors (2x6). 

The idea behind option 2 is that the primary headers are better laterally braced (think direct wind loads on the garage doors).  Whereas with option 1 the pony wall creates a hinge that allows the wall to buckle out of plane.

As far as lateral strength (shear strength) either option would be sufficient.

Which of the two methods would be easier to frame?  Any other thoughts?



Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline Don_P

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Re: PFH: Dropped Header vs. Raised Header
« Reply #1 on: March 15, 2014, 05:05:46 PM »
This is a link to the Dropped Header Design Guide;
http://i-joist.org/pdf/WIJMA%20Dropped%20Header%20Design%20Guide%20(11-7-07).pdf

That said, I lean towards jamming the header up tight to the top plate for out-of-plane lateral bracing, the difference in framing labor isn't much different either way, there are a few more sticks in #2.

Very few RDP's bother to keep up with the codes... and I'll follow my Mama's advice  :) To a large extent they operate outside of the prescriptive portions of the code. I am curious about the other methods they suggested.

Offline hpinson

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Re: PFH: Dropped Header vs. Raised Header
« Reply #2 on: March 16, 2014, 06:27:47 AM »
My garage is framed as in #1, with 2x6. The garage exterior is covered in Stucco.  Over the years it is interesting to see where the stress fractures in the stucco occur. They generally follow the short vertical top 2x6's that are above the header. Almost every 2x4 shows a stress crack. They move a tiny bit every time the garage door opens and closes.

Offline Medeek

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Re: PFH: Dropped Header vs. Raised Header
« Reply #3 on: March 16, 2014, 07:45:21 AM »
My garage is framed as in #1, with 2x6. The garage exterior is covered in Stucco.  Over the years it is interesting to see where the stress fractures in the stucco occur. They generally follow the short vertical top 2x6's that are above the header. Almost every 2x4 shows a stress crack. They move a tiny bit every time the garage door opens and closes.

Are the crack lines horizontal where the pony wall meets the garage door header?  Can you take me a quick snapshot and post it?
Nathaniel P. Wilkerson, P.E.
Designer, Programmer and Engineer

Offline hpinson

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Re: PFH: Dropped Header vs. Raised Header
« Reply #4 on: March 16, 2014, 07:50:27 AM »
I can, but is it going to be a day or two before I can get to it.  Saint Patrick's day is demanding for Irish Dancers and musicians!