Brick Veneer Height?

[SteelPE]

Forgive the rudimentary/shortness of this question as I have to run out the door in a minute.

I am currently working on a project that is a tall 2 stories and is made up of 8 different cladding materials (a real nightmare). One cladding material they are using is veneer CMU and veneer brick. The code being used is IBC 2015. The project has large openings which is requiring a hung lintel system over some sections of the building (I say some because… see comment about 8 different siding materials above). We have some sections of brick veneer “piers” around the building that are full height and other sections with mass CMU/brick veneer and others that go over large curtain wall systems.

Currently this CMU/brick veneer is topping out at 33’-0”. My question is in regards to the code height limit of 30’-0”. Do we really need to relieve the brick veneer that is over the 30’-0” limit (I know the code allows gables to go to 38'-0")? It’s just so close. In some areas, due to the architectural layout, there is just nothing to support the brick on (due to floor openings and stairs).

 

[dhengr]

SteelPE:
There isn’t anything magic or sacrosanct about the height of 30’, it’s the number they selected, in a height range they knew had worked over the years, thus the gable exception. I would get with the AHJ right away, with a real meaningful prelim. plan for handling these problems, to show that you are serious about handling them properly. Then, you will come back when the plan and details are fully developed for final approval and acceptance. The intent is to know that you won’t just be turned down outright, to find out what particular items they would need addressed for acceptance, and to get the ball rolling without springing any surprises on any of the parties involved, owner, Arch. GC, AHJ, you, etc.

As I see it, the biggest problems will be flashing, control joints btwn. different materials, differential movement of various materials, etc. More than code min. brick ties of the best quality and movement potential, to a sufficient backing structure, etc. Lintels and the like will need special attention, and all of this should be really well detailed, spec’d. and managed/inspected. With 15 different subs. working elbow to elbow, on just the 8 different exterior cladding materials, this is going to take some serious planning, detailing, coordination and inspecting. With your prodding and direction, to protect and control what you can possibly do (and your liability too), this should mostly fall to the Arch. After all, it’s his baby and if it is ugly that’s not your fault. If you can go to the AHJ, in later meetings or at permit time, showing buy-in from all parties, you might give him some reason to go along with it. Otherwise, you are just going to have 5 design entities and 15 subs all pointing fingers at each other when things go south. I’ve seen some real nightmares on large bldgs. projects where differential movement and proper joining of different cladding materials was not properly addressed.

 

[masonrygeek]

Actually, there are no height limits for a brick veneer/concrete block backing in TMS 402. If you notice the 30' height limitation is for BV/SS and BV/WS. But... you still should consider the differential movement between the veneer and backing. Generally, whenever you are close to maximum height, I would look at three things (including all of the items mentioned by dhengr): the type of tie, the amount of differential movement and the top of wall detail.
You shouldn't use corrugated wall ties, but specify adjustable type ties which are very common. (in fact, IMHO there is never a place for corrugated ties in commercial construction).
Consider the differential movement at items that penetration through the wall such as windows, balconies, etc. With 33' there isn't a lot of differential movement like there would be if you were trying to go 50'. Look at how the windows are attached and potentially provide a larger soft joint around the window.
What type of coping or top of wall detail is used? Again, the brick veneer will be growing and the block backing will be shrinking. Is the amount of differential movement accommodated in the detail?

A good source of info on this is BIA's Tech Note on cavity walls (TN28D)

https://www.gobrick.com/docs/defaul...documents/technicalnotes/tn28d.pdf?sfvrsn=46.

 

[SteelPE]

Thanks for the great information.

I don't know how much if any of the items you two listed I have any control over. I can say that the section we have going up without structural relief is CMU backed.... without any windows (see attached).

On the attached elevation the stair well is encased in CMU and runs between grids B.9 and B.4 We have structural steel that runs from A - B.4 and B.9-D along this elevation. We plan on having a hung relieving angle from A-B.4 but have nothing to attach to from B.4-B.9. FC-2 is a dark colored metal siding material.

 

[masonrygeek]

Seeing your elevation gives me a better idea of what you are working against. I would say, since you have to support the brickwork above the main entry glazing, just make that a shelf angle (I like that term better than relieving angle) all the way across as shown in the attachment. I'm not sure how the wall turns back at B.9, but the angle could turn with the wall and be attached to the block backing (I think that is what you said is between B.4 and B.9). Then you have the brick piers that can expand and contract without impacting the brick above the shelf angle and you would meet the prescriptive code minimums. I think you *could* just have a shelf angle or fixed lintel just above the main entry glazing with vertical expansion joints on both ends and just have the remaining masonry bear on the foundation, but that's your choice.

Oh, and tell the architect to place a bond break or flashing between the CMU base and the brick veneer since they are materials that move differently. Otherwise, the brick will expand and crack the CMU.