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MASONRY WALL CONTROL JOINTS

To control shrinkage cracking, control joints should be placed and spaced to divide walls or wythes into a series of rectangular panels. Control joints should also be placed in areas of high stress concentration where cracking is most likely to occur. Normal spacing and desirable locations for control joints are noted in the table below. Control joints should not be located at openings due to construction and performance problems and minimum reinforcement requirements. For non-structural partitions, the minimum reinforcement around openings will consist of one No. 4 bar at each side and at the top and bottom of each opening. Reinforcing bars will extend 24 inches beyond the edge of the opening.

Vertical Spacing of
Joint Reinforcement
With 2-#9 wires
(in.)		 Maximum Ratio
of Panel
Length to
Wall Height
(L/H)		 Maximum
Spacing of
Control Joints
(ft)
None218
16324
8430


Recommended control joint locations

a. At regular intervals as noted in table above.
b. At changes in wall height or thickness. (This does not include at pilasters.)
c. Near wall intersections in "L", "T", and "U" shaped buildings at approximately 50% of the spacing required above.
d. At other points of stress concentration.


Control Joint Details
(1)A keyway or interlock will be provided across control joints as a means of transferring lateral shear loads perpendicular to the plane of the wall. Transfer of bending moments or diagonal tension across control joint keyways or interlocks should not be assumed. Control joints should be weathertight.
(2) Control joints in concrete masonry unit walls will be continuous and vertical. Control joint details must provide an uninterrupted weak plane for the full height of the wall, including intermediate bond beams and masonry foundation walls.However, reinforcing steel in structural bond beams must be continuous through control joints. Control joints need not extend into reinforced concrete foundation walls.
(3) Control joints divide walls into panels which are separate structural elements. Hence, locations of control joints effect the relative rigidity of wall panels and, in turn, the distribution of lateral (seismic or wind) forces and the resulting unit stresses. Therefore, adding, eliminating or relocating control joints, where the lateral load resisting system is sensitive to control joint location, will not be permitted once the structural design is complete.
(4) The control joint location criteria above applies to all walls exposed to view where control of cracking is important. For walls not exposed to view, a control joint spacing of four times the diaphragm to diaphragm height or 100 feet, whichever is less, may be used.


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