Rusting steel lintels over windows typically cause what type of cracks in masonry?

Rusting steel lintels over windows lead to horizontal cracks radiating from the corners of the windows due to the expansion of the rusted steel. As steel rusts, it undergoes a significant increase in volume, which exerts outward pressure on the surrounding masonry. This pressure causes the masonry to crack horizontally as it tries to accommodate the expanding material.

The particular stress concentration around window corners typically exacerbates this phenomenon, as these areas are often weaker points in the structure. Thus, the manifestation of cracks is most observable in a horizontal pattern radiating from these corners, indicating direct damage related to the compromised lintel support. Understanding this relationship between rust and the resulting structural damage helps inspectors identify potential maintenance issues in masonry buildings.