What are the two likely causes of step cracking above a window in an exterior brick veneer wall?

Step cracking above a window in an exterior brick veneer wall is often indicative of structural issues related to the masonry's support during events such as settlement or excessive load. One significant cause of step cracking is a short lintel. A lintel is a structural element that spans an opening, such as a window, and bears the weight of the materials above it. If the lintel is too short for the opening, it may not adequately support the weight of the bricks and can lead to cracking as the brickwork settles.

Additionally, rusted lintels can also contribute to such cracking. As metal lintels corrode over time, they can expand, leading to stress in the surrounding brick. This stress can cause the bricks above to crack and create the step pattern that is typically seen in these situations.

Thus, the presence of either a short or rusted lintel is likely to result in structural inadequacies that manifest as step cracking above windows in brick veneer walls.