I have seen many masonry walls built with one-third bond instead of the traditional half bond in a running bond pattern. When is one-third bond used?
One-third bond is used whenever the length of the unit is three times the depth of the unit. This is the case with Roman, Norman, and utility modern brick units, which are nominally 12 inches long and 4 inches deep. It is also true with nonmodular units that are nominally 3 inches deep, 9 inches long, and 3 inches high. The one-third bond is needed to properly form corners, offsets, and returns at windows. In these situations, the brick units are turned 90 degrees so that the end of the brick is exposed. This will determine the bond pattern. The one-third bond gives a different appearance and a different character to the masonry wall.
It is sometimes the depth of the unit that will determine the bond pattern. The thickness of the 3-inch-deep nonmodular units is approximately 5/8 inch to 3/4 inch less than standard modular units. This makes the walls slightly lighter and can permit the use of wider cavities when, due to space constraints, the overall thickness of the wall must be minimized.