Concrete Floor Control Joints

Typical concrete garage floors may not always include control joints, but in most cases they are present and must be properly addressed before applying an epoxy floor coating  system. Control joints, also known as contraction joints, are intentional “planned cracks” designed to manage the natural shrinkage of concrete as it cures and to help prevent random cracking, ensuring long-term durability and coating performance.

When present, control joints often appear as a large plus sign (+) pattern that divides the garage floor into multiple sections. These joints may be V-shaped grooves approximately 3/8” wide formed during the initial concrete pour, or more commonly, saw-cut joints about 3/16” wide and up to 1” deep created 18–24 hours after the concrete has partially cured. Proper identification of these joints is critical for achieving a professional epoxy installation, strong adhesion, and a seamless, long-lasting finish.

Both types of control joints run from one end of your garage floor to the other. Simply put, “control joints” are in a concrete floor to control the direction the concrete will crack in. The concrete WILL crack! Because concrete cracks with expansion and contraction, these joints create a weakened line in the concrete that encourages cracks to follow the line within the joint.

Control joints help control cracking and relieve stress by directing movement along a planned path, preventing cracks from traveling unpredictably across the surface of your concrete floor. This reduces the risk of unsightly spider web cracking and helps maintain a clean, uniform appearance for your epoxy or concrete coating system.

They also allow adjoining concrete slabs to expand and contract without damaging each other, improving the overall structural integrity and long-term performance of the floor. The bottom line is simple: concrete control joints are essential and must be properly honored to ensure a durable, professional-quality epoxy floor installation.

Flake floor control joint handling

Concrete floor control joints should be thoroughly cleaned of all dirt, dust, and debris prior to coating. Any chipped or damaged edges should be repaired using our high-strength KreteBond Concrete Crack Filler, then ground flush and straight with an angle grinder to maintain uniform joint width and clean, professional lines for optimal epoxy adhesion.

During a typical epoxy flake floor the multicolor flakes, and clear topcoat are applied over the surface and may naturally flow over the edges and slightly into the joint. The final appearance will depend on the joint condition and installer technique, but proper preparation ensures a consistent, high-quality finish.

After the flakes have been fully broadcast and cured, the control joints must be reopened and cleaned out. Use a floor scraper or putty knife to carefully cut along the joint and remove any excess flakes or coating buildup. Once the joints are clean and defined, proceed with applying the protective topcoat for a durable, professional-grade epoxy floor system.

NOTE: A completely smooth surface where control joints are filled and hidden, is not recommended. Due to natural concrete expansion and contraction, stress can transfer through the slab and cause cracking in the epoxy base coat, flake layer, and topcoat, compromising the long-term durability and performance of the coating system.