Gable end framing -- hinge effect?

[rothbard]

I looked back through this forum and didn't find any examples of the 1 story 20x30 being built with balloon framed gable ends.

I was wondering if maybe others had found some way to mitigate the hinge effect as seen above when wind force acts upon a platform framed end?

the 20x30 single story design has an open beam ceiling.  This doesn't leave a diaphragm or support I can think of to stop the above hinge effect at the gable end other than staggering the sheathing.

Curious if I had missed something?  The plans don't call out baloon length studs here either.  I looked for any details providing hinge support.  I'm going to plan on just baloon framing the 2x6 gable end all the way to the roof I guess since those ends aren't "load bearing" as the roof is steep enough at 10:12 that the ridge board has essentially no downward force.

I found this particular video of the same consideration for a similar design

[rothbard]

Thought about this some more.  Approach looks like it can be split per publication I found that suggest ceiling diaphragm only needs to go 40% of width down the length of the building to brace the hinge.  Therefore rear gable will be platformed and front will be balloon framed.

I know no one probably cares, but if years and years from now someone else is building the single story 20x30, take note to consider altering the plans to platform frame the rear wall, braced by the attic diaphragm.  And then to frame the front cathedral gable end with balloon/rake wall from top to bottom.  

Note: not engineering advice

[Don_P]

R602.3  Studs shall be continuous from support at the sole plate to a support at the top plate to resist loads perpendicular to the wall. The support shall be a foundation or floor, ceiling or roof diaphragm or shall be designed in accordance with accepted engineering practice.

That whole section is worth studying 

[rothbard]

Thanks Don!

Yep that is exactly what I was worried about and thank you for showing the place where they point it out. 

The single story 20x30 plans has a 8' ceiling on one end so it looks like the ceiling diaphragm has it covered to platform frame the back.

On the other gable end of those plans has an open beam ceiling which means per 602.3 there I need to go the full ~16' with the studs from sole plate to the roof.  That means thankfully only one of two gables needs the full span rake.  Fortunately the design does not have that gable end as supporting a ridge beam so the studs can use the non load bearing length.

Maybe I've missed it but the single story 20x30 materials list doesn't ANY studs beyond 8'.  I might recommend that if I haven't missed something, they might make note of the need for longer studs if it is built with the open beam as designed.

Also really appreciate your prior posts going back.  They were instrumental in convincing me to do the full perimeter cmu foundation.

[Don_P]

Do confirm that you do not need to design the ridge as a supported beam.

R802.5.2 Ceiling joist and rafter connections.
Where ceiling joists run parallel to rafters and are located in the bottom third of the rafter height, they shall be installed in accordance with Figure R802.4.5 and fastened to rafters in accordance with Table R802.5.2(1). Where the ceiling joists are installed above the bottom third of the rafter height, the ridge shall be designed as a beam in accordance with Section R802.3. Where ceiling joists do not run parallel to rafters, rafters shall be tied across the structure with a rafter tie in accordance with Section R802.5.2.2, or the ridge shall be designed as a beam in accordance with Section R802.3.

[rothbard]

Roger that.  Will put the ceiling joists in the back parallel at the bottom of the rafter, and the ties in the open ceiling in the bottom 1/3 of the rafters so that the ridge does not become a beam.