Pony/Cripple Wall Hinge

[youngblood30]

I recently had a look at a set of plans with a new 2x framed pony/cripple wall(about 12-18" tall) built on top of an existing 2x framed wall(9' tall) for a 2nd floor addition. They clearly just wanted more ceiling height on the first floor while constructing the new 2nd floor addition on top of the pony wall.

It looks like a local architect stamped this but I don't see any details to address the clear hinge point this creates. I know this is done a fair amount with foundation walls up north but without kickers or balloon framing I don't see how this can work especially in a higher wind zone. What gives here?

 

[phamENG]

Sounds like a good example of why we carry errors and omissions insurance!

Seriously, though - good catch. Being in Florida, that could be a big deal. I'm in Coastal Virginia, and I've seen walls built like that that have failed at the hinge. Now, was anything else done? Did they strip sheathing down the wall and lap it with plywood? Did they strap every stud? There's ways of convincing yourself it'll work, but the only way I've ever been happy with it is pulling off the top plate and adding full height studs.

 

[XR250]

I've done the strapping both sides of the wall on a 12" extension. Didn't feel great about it but it passed the "shake test" pretty nicely. I agree that cutting the top plate and sistering is the way to go.
I have also lapped the cripples studs across the face of the floor joists to create a moment connection in order to brace the hinge.

 

[kissymoose]

I'm dealing with this right now actually. To increase the ceiling height of an existing house we're going to attach the studs to the sides of the 12" deep joists. The additional height is only a foot, so the moment required to fix the studs to the joists is about 100 ft-lbs which can easily be done with a few nails between the studs and joists. And the 1.6 load duration factor really makes it easy.

 

[KootK]

Clever. Almost like a tall OWSJ bearing seat.

 

[youngblood30]

kissymoose...so you would need a stud to support the flr. joist and one nailed to the side of it all sitting on the existing top plate? I wouldn't think the nails would also take the vertical loads as well as the moment...maybe I am seeing it differently...would love to see a detail on this.

 

[kissymoose]

 

[phamENG]

Nice detail, kissymoose. I think I'd want to see the existing sheathing pulled down at least 2 feet and then run the new sheathing up. Can't point to a quantifiable proof that it's required - I'd do it in the name of continuity between existing and new.

 

[youngblood30]

Nice! That is what I was seeing...they used floor trusses which would require an extra bearing stud and the face nailed stud would need to get notched at the top where the horiz. ribbon board runs...I guess you could stop it short and just make sure you have enough nails. Very nice detail tho...thanks for sharing.

 

[kissymoose]

Thanks KootK.
PhamENG - That's a good point, I can appreciate doing so.

 

[KootK]

Can't point to a quantifiable proof that it's required

I think that I can, at least for the general case where there's diaphragm shear at play.

 

[phamENG]

Touche. There's probably an uplift load path issue, too - especially if there's an overhang.

Rephrasing: I haven't put in the time to quantify a reason to do it, but even doing so I'd do it in the name of continuity between existing and new.