huangyhg

masonry control joints at intersection walls
trying to determine which is correct... our general notes read such that a masonry control joint shall be placed at all masonry wall intersections. however, we also show a typical detail for a t-shaped intersection where t-shaped horizontal joint reinforcement is called for to maintain horizontal joint reinforcement continuity - thus making it impossible to provide a vertical control joint at the location. the same question would also apply to corner conditions.
from my limited number of site visits, i don't recall seeing vertical control joints at these locations. however, it would seem to make sense if they were located there to prevent cracks from temp/shrinkage and movement. we typically specify joints be placed at 20 feet on center, but other than the general note, do no make reference to providing them at corners or intersections.
any advice or suggestions would be greatly appreciated!
corners and intersections of structural (load bearing or shear walls) walls should be tied together with no joint. we normally put joints and tie together walls where partition walls intersect a structural wall.
also provide joint and tie where two walls join but are supported by different foundations (for example frost wall foundation and thickened slab). this is to provide for possible differential movement.
i would apply your general note to t intersections only. it is much more common for cmu corners to be fully bonded, (with intersecting horizontal joint reinforcing) than to have a true control joint.
t intersections are handled in a variety of ways, and can be somewhat confusing with respect to whether they function as control joints or not. the pca "concrete masonry handbook" has a section "intersections" that does a nice job of sorting thru this. you can have a fully bonded or tied intersection with mortar joint, or a 2 way control joint whereby you use sealant in lieu of mortar joint, with no ties or joint reinforcing crossing the joint. you can also have a one way control joint by using sealant, with a 1/4" "z" strap (say 2" end legs, 24" long). the strap provides lateral support for the (continuous) abutted wall, but has enough flexibility parallel with the abutted wall to allow the abutted wall to move without distressing the intersecting wall.
concur with mrengineer, as i have shown "z" staps at corners. it is interesting to note featherlite, national concrete masonry association does not specifically address this in tek 5 9a cmu corner details, tek 10-2b control joints for cmu walls - empirical method or tek 10-3 control joints for cmu walls - alternative enginered method. tek 10-2b does show joints 1/2 control away from corners, between main & intersecting wall (assume main wall is load bearing and other is partition wall or this would not apply), at changes in wall height, at pilasters and changes in wall thickness and adjacent to openings. if you review noted references it should help in providing adequate control joints in cmu walls which is not an exact science, but does require good engineering judgement, using national concrete masonry association recommendations. hope this helps.

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