What is the primary function of a control joint in masonry?

The primary function of a control joint in masonry is to control cracking. Control joints are specifically designed to accommodate the natural expansion and contraction that occurs in masonry materials due to temperature changes, moisture variation, and other environmental factors. By providing a predetermined location for the material to crack, control joints help prevent random cracking throughout the masonry structure, which can compromise its integrity and aesthetic appearance.

Masonry can be susceptible to cracking due to its rigidity, and without these joints, stress from movement can lead to unsightly fractures. The implementation of control joints helps maintain the structural integrity of the masonry while allowing for necessary movement, thus ensuring longevity and durability in construction.

While control joints might have secondary benefits related to aesthetics, drainage, or load-bearing aspects, their primary and most significant role is in managing the cracking that can occur in masonry due to internal and external stresses.