Which type of bond is considered the weakest?

The weakest type of bond among the options provided is indeed the stacked bond. This type of bond is characterized by its alignment where bricks or stones are laid directly on top of each other in straight, horizontal rows without any offset. Because the stacked bond lacks any staggering of the joints, it creates vertical lines of weakness throughout the structure. This can lead to reduced structural integrity, making it susceptible to issues such as cracking and settling, compared to other types of bonds that provide enhanced strength and stability through staggered placements and interlocking patterns.

In contrast, the other bond types—such as running, Flemish, and concave bonds—have designs that interlace bricks or stones in ways that distribute loads more evenly and bolster the overall strength of the wall or structure. By reducing vertical joint lines and providing interlocking mechanisms, these bonds increase resistance against structural stress. This understanding is crucial for anyone involved in construction, as choosing the appropriate bond can directly affect the durability and safety of the construction project.