What is the primary purpose of control joints in masonry?

Control joints in masonry are primarily designed to accommodate thermal expansion and contraction within the material. As temperatures change, masonry can expand when heated and contract when cooled. Without control joints, the stresses induced by these movements could lead to cracking or structural failure. The incorporation of control joints allows for this natural movement, effectively reducing the risk of damage to the masonry and maintaining the integrity of the structure.

While aesthetic appeal, structural support, and drainage play significant roles in masonry work, they are not the primary function of control joints. The main goal is to manage the inevitable movements that occur due to temperature fluctuations, ensuring that the masonry remains durable and resilient over time.