**Step Cracks in a Concrete Block Wall **
Vertical movement in a concrete block or brick wall might appear as either vertical cracks but more often as step cracks in which the crack pattern follows the mortar joints between the masonry units in a stair stepping pattern.
Step cracks are very common in concrete block walls. It is not unusual for cracks to originate as horizontal cracks, and over time, begin to step down, or up, along the mortar joints.
Typically, there is a tremendous amount of pressure pushing from the outside, whether it be expansive soil, tree roots or other catalysts.
If there is no pressure coming from the exterior, sometimes the wall bearing the load of the house simply cannot handle the weight, and begins to fatigue.
Unlike horizontal or vertical cracks where the opposing sides of the crack are pulling away from each other, in a step crack your wall is pulling apart from itself in all four directions and needs to be stabilized accordingly.
At this point, there is very little structural integrity left in the wall, and it needs to be stabilized as soon as possible. If bowing of the wall has not already occurred, it will most likely begin soon thereafter.
Hope this helps