What additional step is required when constructing a stack bond pattern block wall, compared to a common bond wall?

When constructing a stack bond pattern block wall, the requirement for joint reinforcement to be added to every second course is essential for structural stability. In a stack bond wall, each block is aligned directly on top of each other without overlapping, which results in less lateral strength compared to a common bond wall where blocks are staggered.

The lack of overlap means that the wall is more vulnerable to cracking and shifting. Therefore, adding joint reinforcement helps to enhance the wall's overall strength and stability, allowing it to better resist lateral forces, such as wind or seismic activity. This reinforcement typically involves using steel reinforcement bars or mesh placed within the mortar joint every second course, providing necessary support and aiding in the structural integrity of the wall.

Other options do not specifically address the structural requirements needed for stack bond walls. Adding insulation, using larger blocks, or incorporating more mortar into the mix would not adequately compensate for the lack of bond strength created by the formation of a stack bond pattern.