Honoring Concrete Control Joints
What control joints are, why they matter, and how to handle them when you install a DIY epoxy flake floor.
What Are Concrete Control Joints?
Typical garage and basement concrete floors might not have “control joints.” However, in some cases, control joints will be present and must be dealt with accordingly.
If control joints are present, they usually look like a big plus sign (+) that divides your garage floor into what appears to be four separate concrete slabs. These joints can be deep 3/8" wide V-shaped grooves made during the pouring of the concrete, or saw cuts, usually a minimum of 3/16" wide and 1" deep, made 18–24 hours after the concrete is semi-cured.
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 that encourages cracks to follow the joint.
This discourages cracks from following a more resistant line across the surface, eliminating spider-web cracks in an otherwise clean floor. Control joints also help prevent adjoining slabs from damaging each other as they expand and contract.
The bottom line: concrete control joints are needed and should be honored, meaning, not tampered with prior to an epoxy floor coating.
How to Handle Control Joints in a Flake Floor
Concrete floor control joints should be cleaned out of dirt and debris, and chipped edges patched with our crack filler. Repaired edges should be ground straight in-line with the control joint using an angle grinder for joint-width uniformity.
A typical epoxy flake floor or decorative metallic epoxy floor installation allows the epoxy, optional color flakes, and clear coating to flow over the edges of the control joint and possibly into the bottom of the joint. How neatly this is done depends on the actual joint and the installer.
Once the flakes have been broadcast and cured, the control joint should be cleaned and overlaying flakes removed. Use a floor scraper or putty knife to cut into the joint and cleanly remove flakes over the joint. Once all excess flakes have been removed, the garage flake floor top-coat can be applied.
NOTE: For a completely smooth concrete floor where the control joints are to be hidden, we do not recommend it. Do this at your own risk. The natural contraction and expansion of the concrete can crack the base-coat epoxy, flake chips, and top-coat over a filled control joint.
Ready to Prep and Install?
Now that you know how to honor your control joints, get your concrete prepped and roll out your weekend floor.