Page 474 - Forensic Structural Engineering Handbook
P. 474
MASONRY STRUCTURES 13.19
Because concrete masonry has net contraction (shrinkage), control joints in concrete
masonry widen. They may, therefore, be filled with mortar or grout but must be free of rein-
forcement, stiff flashing, and debris. Because clay masonry has net growth, expansion
joints in clay masonry must be free of mortar, reinforcement, stiff flashing, and debris.
Figures 13.4 through 13.18 illustrate masonry crack patterns. Grimm 18 discusses
masonry design for crack control. Movement joints should be placed at the following loca-
tions: at beam soffits; under shelf angles; at wall intersections; at horizontal intervals of
FIGURE 13.4 Facial separation cracks.
Small diagonal tension
cracks in vertical array
Corner expansion Shelf angle discontinuous at corner Corner expansion no expansion joint
No shelf angle-
Shelf angle with expansion joint
Elevation
FIGURE 13.5 Differential vertical movement at corners due to discontinuity of shelf angle.
