This is a common question that your friends at A-1 Foundation Crack Repair field on a recurring basis. Step cracks are very common occurrence in concrete block walls. A recurring form of home foundation damage is 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 weakens over time. Make sure to not collocate excessively heavy objects such as safes, major appliances, cinder block, etc.
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.
Of course step cracks threaten commercial property as well. We specialize in commercial foundation crack repair as well.