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Offsets and Setbacks. Parallel walls will expand toward
an offset, rotating the shorter masonry leg, or causing
cracks within the offset, as shown in
Figure 4a
. Place
expansion joints at the offset to allow the parallel walls to
expand, as
Figure 4b
illustrates. Expansion joints placed
at inside corners are less visible.
Openings. When the spacing between expansion joints
is too large, cracks may develop at window and door
openings. In structures containing punched windows and
door openings, more movement occurs in the brickwork
above and below the openings than in the brickwork
between the openings. Less movement occurs along
the line of openings since there is less masonry. This
differential movement may cause cracks that emanate
from the corners of the opening, as in
Figure 5
. This
pattern of cracking does not exist in structures with
continuous ribbon windows.
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