FTAO straps

[FloydLloyd]

Any thoughts about applying the FTAO straps to the inside of the wall, sheathing on the outside?
10x12 porch addition, loads are moderate, strap tension 680 lbs, hold downs 450lbs, unit shear on piers ~ 200 plf. Sheathing is blocked.
Thanks for your response,
D

 

[phamENG]

I don't like it. Those things are sketchy enough (don't get me wrong, I love 'em and spec' 'em)...I want that tie force directly at the sheathing. Asking it to pass in and out of studs and poorly cut blocking and getting all the fasteners just right? No, thanks.

 

[JoshPlumSE]

Conceptually, there isn't a problem with it. But, like phamENG, I haven't seen it done this way and it gives me the "ick". It should be cheaper and easier to put it on the outside. Is there an architectural consideration that is preventing this?

 

[CURVEB]

Search APA for this topic. There is a paper where they discuss this issue.

 

[CURVEB]

Long story short, I believe it is permitted as long as you have solid blocking between the strap and the sheathing, and nail the sheathing to the blocking to transfer the force.

 

[KootK]

I like exterior better as well but am fine with the interior option if that's what it takes to make people happy. After all, a beam-column in tension is a much better thing than a beam-column in compression. Depending on the gauge of those straps, interior side fastening may not make a friend of your drywaller however.

 

[driftLimiter]

I would think about edge nailing the plywood to the members that have a strap on the back side. Full depth blocking members used like this need to be able to develop the strap capacity on the sheathing.

 

[manstrom]

I allow on the inside. Then I can see that they actually installed them. If it's outside, then it's under tyvek and I can't see anything.

In a perfect world, outside (on sheathing) is better.

I'd should look up the APA paper.

 

[FloydLloyd]

Thanks for responses.
Its a single opening wall, and the two end 'piers' are 21". Blocking is required for piers less than 24".
I couldn't decide if the straps on inside represents an eccentric condition. Seems like that creates shear flow through the blocking which is fine. I'll take a look for the APA article on this subject.
I like the idea of nailing the sheathing to the blocking opposite the straps.

ICYMI - Just in case you haven't seen the APA FTAO calculator (and I don't know how you could design an FTAO wall without it) here's the link.

Yesterday was FTAO, today is a cantilevered diaphragm. Contractors are keeping me busy.

Thanks again.
D

 

[KootK]

Full depth blocking members used like this need to be able to develop the strap capacity on the sheathing.

Does the strap tension not need to be developed into the sheathing regardless of which side of the blocking the strap is installed? Your comment has me worried that I'm not grasping something important about the load path used in FTAO system.

 

[KootK]

I like the idea of nailing the sheathing to the blocking opposite the straps.

Me too from a fastener congestion perspective. With the strap under the exterior sheathing, I worry that the fasteners from the sheathing to the blocking will wind up right on top of the fasteners from the straps to the blocking and wind up disintegrating the blocking (good reason for more skookum blocking).

I couldn't decide if the straps on inside represents an eccentric condition. Seems like that creates shear flow through the blocking which is fine.

I would say that your intuition with that is pretty much spot on. The eccentricity would be resolved by way of toe nail or clip connections at the ends of the blocking as I see it. Only the studs at the start and end of the strap run would "feel" an unbalanced, out of plane load as I see it.