Page 169 - Masonry and Concrete

Masonry Construction Techniques
168 CHAPTER FIVE

should be recessed from the face of the
3
BUILDING PAPER wall about 4 in. so the joint can be
caulked after the wall is finished.
GROUT FILL
Control Joints: Control joints are contin-
uous, weakened joints designed to accom-
modate the natural shrinkage of concrete
masonry in such a way that cracking will
occur in straight lines at these joints rather
RAKE AND
than at random locations (Figure 5-30).
CAULK JOINT
Control joints also must incorporate a
tongue-and-groove type key so that adjoin-
ing wall sections resist wind loads
together, but still expand and contract
CONTROL
independently. Control joints in concrete
JOINT UNIT
masonry walls that are required to keep
out moisture must be sealed against leak-
age. To do this, the mortar is raked out
before it hardens to a depth of 1/2 in. to
RAKE AND
3/4 in., which will allow caulking for
CAULK JOINT
weather resistance. Concrete masonry
always shrinks more than it expands, so
even though control joints contain mortar,

PREFORMED they can accommodate thermal expansion
GASKET and contraction which occurs after the ini-
tial curing shrinkage.
If joint reinforcement is located in every
other bed joint, space control joints at three
times the wall height (e.g., for a 6-ft.-high
wall, space control joints at 18 ft. on cen-
RAKE AND
CAULK JOINT ter). If joint reinforcement is located in
every third bed joint, space control joints
FIGURE 5-30
1
at 2- 2 times the wall height (e.g., for a 6-
Concrete masonry control joints. (from Beall, Chris- ft.-high wall, space control joints at 15 ft.
tine, Masonry Design and Detailing, 4th edition, on center). Joint reinforcement should stop
McGraw-Hill, New York).
on either side of a control joint. It should
not continue through it.

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