What could cause a chimney to lean above the roof?

A chimney that leans above the roof can often be attributed to deteriorated mortar joints. Over time, the mortar that holds the bricks or stones of the chimney together can weaken due to weather exposure, moisture infiltration, and other environmental factors. As the mortar deteriorates, it loses its ability to properly bond the masonry elements, which can lead to structural instability and the chimney beginning to lean. This compromised structure can make the chimney at risk of further damage, and it raises safety concerns, especially if it becomes susceptible to collapse.

While the other factors may also play a role in the overall condition of a chimney, they do not directly lead to leaning as significantly as deteriorated mortar joints. Old age may contribute to wear and tear but does not inherently cause leaning without the specific issue of mortar failure. High winds can affect a chimney’s stability, particularly if the structure is already compromised, but it’s not typically a primary cause of leaning. Lack of paint does not influence the structural integrity of the chimney, although it may lead to other forms of deterioration, such as rust in case of metal components. Therefore, focusing on the condition of the mortar joints is essential in understanding the primary reason for a chimney's lean.