It doesn’t mean that when one thing is not common, it is no longer right.
Perhaps this principle applies to a lot of areas in our lives, but here I will use it in the context of concrete hollow blocks (CHB) laying – because stack bond is so misunderstood, particularly in the Philippines, that most people who have no idea about masonry think it is laughable matter, convinced that it is a wrong way to build a wall. First of all, it is not wrong, it is just not common.
But what is this stack bond anyway?
In technical terms, stack bond is “any wall where the overlap of a masonry unit over the block below is less than one quarter of the length of the block.” In other words, this looks like a wall that is just stacked together in almost perfect, if not perfect, alignment. It is for this reason that this layout is requested: aesthetics. This is contrary to the more common pattern of CHB laying which is the running bond, deemed more acceptable by many.
The running bond, as the name suggests, is the pattern in which the CHB is installed in a running fashion, never lining up with each other when stacked. It is usually created by placing a CHB at the 1/3, ½, or ¼ of the course above and the course below, creating an overlap where no two units are aligned by their left or right edges (or head joints). This is the most common type of masonry worldwide due to its better performance in terms of structural integrity versus the stack bond.
According to the National Concrete Masonry Association (NCMA), two key considerations in the masonry bond patterns is its impact on the compressive and flexural strength of a block wall. However, generally, the running bond is the standard because of its design.
The running bond is about twice as strong in flexure when spanning horizontally as when spanning vertically. Meanwhile, stack bond walls have approximately the same strength regardless if spanning vertically or horizontally having the joints aligned in either direction.
So what does this mean?
If a client wishes to have stack bond as wall, it will involve more cost for the reinforcement to achieve the same strength as the running bond. That is not essentially wrong – someone just wants the wall to be a bit stylish but still within the standards of masonry.