Anchored CMU Veneer Above 30' Height Limit

[Guastavino]

All,

I saw a couple old threads on this that were great, but they are closed and I'd like to take up the issue again. I'm designing a wood framed building (including wood shear walls) with a CMU decorative veneer. The top of wall elevation is consistent (small sloped roof) at 42'. I understand the use of the 30' limit in Chapter 6 of TMS-402, but I'm curious about what people consider the "Alternative design" in TMS-402-08 section 6.2.1 allowing unlimited height.

My thoughts:

1. 42' doesn't concern me as long as I take in to account wood shrinkage, CMU thermal expansion, CMU shrinkage, and inform the architect to account for such details.
2. I know shelf angles to wood are used, but I feel like that is potentially more problematic than going an additional 12'. Those detail introduce wood creep, proper angle installation, expensive difficult to build details, etc.

I'm curious what other things you all would consider for the rational design using 6.2.1, and if you've used it successfully?

Thanks,

Nick

 

[concretemasonry]

rwp -

Are you suggesting a reinforced veneer that spans 13'-4" vertically?

A veneer is usually based on a back-up (CMU or steel stud) with adjustable ties that transfer the horizontal loads back into the basic structure.

It has been done with some CMU or clay veneers, but the detailing is very tricky.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[rwpe]

No...I was responding more to the idea of the 30 foot limit. I agree that ties are needed for the veneer.

 

[Guastavino]

rwpe, I would argue the ties connected to the wood stud backing are what brace the veneer. Then the floor diaphragms brace the wall studs. As for the code requirement, I understand it to be solely a height requirement measured from the foundation.

 

[Guastavino]

So back to this topic:

1. Attached are the elevations of some of the walls. I'm concerned about the veneer cracking at these window locations. What do you all think?

2. I'm still considering using the alternate method of the MSJC, IE supporting the veneer only off the foundation and going above 30'. The BIA (brick folks) have an article on how to do that. It's CMU veneer (decorative stuff), and not brick, but same concepts apply except it will shrink instead of grow.

3. What if I did a combination of supporting the veneer off the structure at the windows at each level, and off the foundation at the areas where the wall goes full height.

Just so everyone knows. The 1'-4" wide Piers between windows are backed with (2) 6x6 glulam posts that support 3-ply 1.75"x14" LVLs at floor levels. So there is a meaty core. Windows are 8'-0" wide.

Any comments?