How Pros Fix a Pitted or Spalled Garage Floor Before Coating It
Pits, craters, and flaking chunks do not disqualify your slab from a coating - but they do dictate the first half of the job.
A pitted garage floor can absolutely be coated - after it is repaired, and never before. Pitting and spalling are the most common conditions we find on older slabs around Waukegan, and the repair sequence is well established: grind the floor open, cut back anything unsound, fill with the right repair mortar, then build the coating over a solid surface. Skip the repair step and the coating maps every crater; skip the grinding and the repairs themselves let go. This is the half of the job that happens before anything glossy appears, and it is where a floor that lasts gets made.
What you are looking at: pitting vs spalling
The two get lumped together but they are different injuries. Pitting is surface erosion - dozens or hundreds of small holes where the cement paste has been eaten away, leaving exposed sand and fine aggregate. Around here the usual driver is salty meltwater and freeze-thaw cycling; the mechanics are covered in our road salt guide, so we will not repeat them. Spalling is bigger material loss - flakes, sheets, or chunks breaking away, often at control joints, slab edges, or over rusting wire mesh. The material-science background lives under spall if you want it. For repair purposes the question is the same for both: how deep does the unsound material go?
Step one: grind and find the truth
You cannot assess a damaged floor by looking at it. The diamond grind that starts every proper install is also the diagnostic: it strips the weak paste and shows exactly where sound concrete begins. Light pitting often half-disappears under the grinder. Deeper damage gets its edges cut back to solid material - a repair feathered onto crumbly edges is a repair that pops out. This is also the point where an honest installer either confirms the floor is a repair-and-coat job or tells you the deterioration runs deeper; we wrote up how that call gets made in resurfacing vs replacement.
Step two: fill with materials built for it
Professional crews fill pits and spalls with fast-setting repair mortars - polymer-modified cementitious products or polyurea fillers, depending on depth and location. What matters about them:
- Bond strength. They grip ground concrete and cure harder than the surrounding paste, so the repair becomes the strong spot, not the weak one.
- Speed. Most reach grindable hardness in under an hour, which is how repair and coating fit in the same install day.
- Compatibility. The base coat chemically accepts them, so the coating runs continuously over slab and repair alike.
Joint and crack treatment happens in the same pass - routed, filled, and flattened so the finished floor reads as one surface. After the fills are ground flush, the slab is effectively resurfaced: flat, sound, and open-pored, ready for base coat.
TL;DR
Pitting and spalling are surface injuries, and surface injuries are repairable. The sequence is grind, cut back to sound concrete, fill with fast-setting repair mortar, grind flush, then coat. In a flake finish the repairs vanish completely. The floor to worry about is the one someone coats without doing any of this.
Pitted floor? Get it repaired and coated in one job
Free on-site assessment - we tell you exactly what your slab needs.
Step three: coat over sound concrete - and hide the history
With the surface rebuilt, the coating goes down as it would on any prepped slab: polyurea base coat, flake broadcast, polyaspartic topcoat. On a repaired floor the full-flake finish earns its keep twice - it protects the slab from the salt that caused the damage, and it visually erases the repair map. Homeowners who watched us patch thirty pits in the morning routinely cannot find one of them by evening. That whole sequence, from grind to topcoat, is what our garage floor repair and resurfacing service covers, and it feeds directly into the standard coating install.
What repair adds to the job
Repair scope is one of the honest variables in any coating quote - a floor needing forty fills takes more material and hours than a clean slab. Size, damage extent, and finish choice are the levers; the full breakdown is on our garage floor cost page. What we will say plainly: repairing during the coating job costs a fraction of what waiting costs, because pitting compounds every winter it stays open. A free quote gets you a real number for your actual floor, measured on site, before any work starts.