Page 253 - Masonry and Concrete

Masonry Veneer

252 CHAPTER SEVEN

METAL STUD ANCHORS WOOD STUD
ANCHOR
FIGURE 7-3
Masonry veneer anchors.

are random, this method of attachment allows greater flexibility in the
placement of anchors for proper alignment with mortar bed joints.
Where a masonry veneer is attached to concrete masonry backing,
such as an above-grade foundation wall, the anchorage is usually in
conjunction with the horizontal joint reinforcement used to control
shrinkage cracking in the CMU. For walls in which the backing and
facing wythes are both of concrete masonry, three-wire joint reinforce-
ment can be used (Figure 7-5a). Two of the longitudinal wires are
embedded in the face shell bed joints of the block and the third wire is
embedded in the veneer bed joint. If the wythes are laid up at different
times, however, the three-wire design makes installation awkward.
Three-wire joint reinforcing should also not be used when insulation
is installed in the cavity between wythes because the wires are too stiff
to allow for differential thermal movement between the backing and
facing wythes. For walls in which the backing and facing wythes are
laid at different times, walls with clay brick facing and CMU backing,
or walls which contain insulation in the cavity between wythes, joint
reinforcement with adjustable ties allows differential movement
between wythes and facilitates the installation of the outer wythe after
the backing wythe is already in place (Figure 7-5b). The adjustable ties
may be either a tab or hook and eye design.
In Seismic Zones 0, 1, and 2, masonry veneer anchors may be
spaced not more than 32 in. on center horizontally and support not
more than 2.67 square feet of wall area. Since the anchors are attached
to the studs and must be embedded in the mortar joints, the stud spac-

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