CONTROL JOINTS

Might someone there be able to help me locate information, maybe in the Building Code Requirements and Specifications for Masonry Structures as to the placement of CJ's in 4" cmu on 6" cmu knee walls? The architect we are working with cites the National Concrete Masonry Institute as requiring CJ placement/location at a length to height ration of 1.5 to 1 so we are expected to put CJ's every 6'. This doesn't make sense to me, 25+ years in the biz and this is a first for this situation. Hoping the MSJC has provided some direction other than the NCMI? 

While the location of control joints is required in concrete masonry work TMS 402/602 do not discuss the location and design of them. NCMA is the resource for that information. There are several reasons for properly locating and installing these control joints. There are a couple of ways of determining locations. One is the use of engineering to determine the spacing and size of the control joints. This is the responsibility of the project engineer. This method uses the coefficient of shrinkage and other aspects of the cmu to determine the size and location. The other method is the empirical method which is described in NCMA TEK 10-02D. Table 1 in this TEK shows a 1.5 height X length as the location. But with shorter walls of less than +/- 16' a maximum of 25'-0" is recommended. If your designer does not locate the joints I would recommend using a 22-24'-0" spacings per Table 1. I am attaching other Tek Notes for you to use or pass on to the project engineer. Since you have a 4" cmu veneer I am including NCMA TEK 10 04 for veneers. I hope this works for you. If you need to discuss this further please call me.

Be Safe and RAISE the LINE.
Jerry Painter, FASTM

Additional Information: 
NCMA TEK 10-02D
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NCMA TEK 10 04