What is the primary purpose of an expansion joint in stucco?

The primary purpose of an expansion joint in stucco is to allow for thermal expansion and contraction. As temperatures change, materials expand when heated and contract when cooled. Without expansion joints, the stucco could crack or become damaged as it tries to accommodate these natural movements. The expansion joint provides a buffer, allowing the materials to move freely and reducing the risk of structural damage.

While aesthetic appeal, structural support, and reducing installation time are important considerations in construction, they do not address the specific function that expansion joints serve in accommodating thermal movements. This makes the choice centered on managing expansion and contraction the most relevant and critical reason for the inclusion of expansion joints in stucco applications.