Almost every concrete floor has some cracks — concrete cracks; that's what it does. The question isn't whether cracks exist, but which ones need attention before a coating goes over them. Some are harmless and coat fine with proper prep; others signal a problem that has to be addressed or the coating will fail with the crack. Here's how to tell the difference.
Hairline and Shrinkage Cracks
Fine hairline cracks from normal concrete shrinkage are common and usually stable. They don't move, so a coating bridges them fine after proper surface prep. They may show faintly through a solid or metallic finish and disappear under a flake broadcast. These don't need structural attention — just the normal profiling every coating requires.
Wider or Moving Cracks
Cracks wider than a hairline, or cracks that open and close with the seasons, are a different matter. A moving crack will telegraph through a coating and eventually crack it, because the coating can't flex with the movement. These get evaluated and repaired — typically routed and filled with a flexible material — before coating. Ignoring a moving crack just hides it temporarily.
Displacing or Settling Cracks
If the concrete on one side of a crack is higher than the other, or a crack is widening over time, that points to settlement or a structural issue. Coating over it without addressing the cause means the coating fails as the slab keeps moving. We tell you honestly when a crack needs a structural look before any coating or resurfacing — see our joint filling vs. crack repair guide for the distinction.
Repair Is Part of Prep
Crack repair that's needed is built into the quote and the prep, not added after we start. We assess the cracks during the estimate, specify what each needs, and include it in your written price. The goal is a coating that bonds to a sound, stable surface — and that means addressing the cracks that matter before the coating goes down.