A control joint is a groove cut into a concrete slab to force shrinkage cracks to form in a straight, planned line instead of randomly. It manages the natural movement of curing concrete before any coating goes on.
A control joint is a groove cut or formed into a concrete slab to create a planned weak point where the slab will crack as it shrinks during curing. Rather than cracking randomly, the concrete cracks cleanly along the joint, keeping the surface looking intact.
Why Control Joints Matter Before Coating
Concrete naturally shrinks as it cures and continues to expand and contract with temperature changes. Control joints manage that movement, and any coating installer needs to know their locations, since joints typically need to be honored or filled rather than coated straight over.
Control Joint vs. Expansion Joint
A control joint manages shrinkage cracking within a single concrete pour and is usually cut partway through the slab. An expansion joint separates two different sections of concrete entirely, using a compressible filler to allow for movement between them, such as where a driveway meets a garage floor.
Practical Tips for Handling Control Joints
Inspect and photograph all joint locations before coating, and decide upfront whether you will honor the joint through the coating or fill it with a flexible joint filler. Never coat directly over an unfilled joint expecting it to stay put, since movement underneath will eventually crack the coating above it.
