Vertical crack in soldier course brick mortar joint

[PSUengineer1]

The attached photo shows a vertical crack in soldier course brick veneer mortar joint, where the soldier coursing meets the running bond brick veneer. Stair-step cracks are in the brick veneer below this area, which are probably from foundation settlement.

What is the cause of the vertical crack in the attached photo? Could it also be from settlement? thermal expansion of materials? No steel lintel observed above window. Not an expansion joint issue (this is a small ranch house). I am looking for a general description of the cause of the crack. thanks.

 

[oldestguy]

Not having a photo of the whole wall, but seeing sun this area, likely the whole wall moves horizontally some due to typical expansion and contraction of brick walls.
The small zone left of the crack likely is restricted some as compared to other wall sections [possibly due to what sits on it. Does not seem to be settlement related. Stair-step cracks are not always settlement related, but can be expansion-contraction related.

 

[dhengr]

PSUengineer1:
I see a window/door opening head and jamb area on the left, along with three courses of normal brick in the upper left corner, as fill courses, at the end of the soldier course of brick. This is a brick veneer, I assume. Mortar bond is normally not as good on head joints (vert. jnts.) as it is on bed joints (horiz. jnts.). I think something is pulling to the left at the upper left corner of the two courses of normal brick, and they are kinda rotating, counterclockwise, about the left end of the second mortar course down, thus opening up the (vert.) head jnt. along with a bit of the adjacent bed joint. Some horiz. force at the head of the window might be enough to do this: a structural header at it’s bearing/reaction; the head trim with all that caulking. There is no vert. loading on those two courses of bricks to counteract this horiz. loading. There could also be some relative horiz. movement, left and right, at the window jamb, as suggested by the oldestguy. That would induce the rotation too.