Masonry Expansion/Contraction Joints

[Hercul3s]

Is it necessary to have Expansion/Contraction joints in CMU backup block walls in a Composite Wall construction? (Brick Veneer and Backup Block)
In other words: if the CMU is not exposed to weather and is an "interior" item, are vertical joints still necessary?
I couldn't find a code section that addresses that clearly.
Thanks!

 

[XR250]

You need them in the brick. If you don't have them in the CMU as well in a composite wall I would think weird in-plane shear forces and maybe bowing could happen.

 

[JAE]

Yes - joints are required.

Attached is a fairly old document - shows spacing recommendations for interior and exterior conditions.
The MIA Masonry Engineering Handbook recommends a spacing of 25 ft. or a maximum length/height ratio of 1 1/2 whichever is smaller....independent on whether the wall is interior or exterior.


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[thaidavid40]

And since the brick veneer will be attached with ties to the CMU backup wall, the brick joints should align with the CMU joints. Though you could have additional joints in the brick beyond those that you have in the CMU.
Dave

Thaidavid

 

[concretemasonry]

There is a difference between a composite wall and a cavity wall with rigid foam in the cavity.

If you use an "eye and pintel" system, the exterior wythe sees different conditions than the interior (temperature/moisture) and can perform well. The ties allow the differential lateral movement of the wythes. Joint reinforcement with diagonal elements and welded brick ties acts differently.

Dick

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

 

[Hercul3s]

Thanks guys!
Sorry for the late response - I was away during holidays!

 

[MikeE55]

Definitely use control joints or you will end up with shrinkage cracks in the block. Brick will expand over time, but the cmu will shrink. I have seen many jobs where the control joints were omitted, and the cmu formed shrinkage cracks.

 

[JLNJ]

I agree that contraction joints are a must in CMU walls.

I espouse the idea that you can increase the length between joints if you have joint reinforcement.