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A single crack, a delaminated patch or a worn hollow does not necessarily mean the whole floor must be recoated, but not every defect can be patched the same way either. Spot repair only lasts when the repair method matches the damage type and the substrate underneath is still sound enough to hold the patch. This article presents the patching and recoating process for each common damage type.
To avoid confusing this article with the overview: the article Localized Epoxy Floor Repair: Patching and Recoating Individual Areas presents the overall sequence from diagnosis to handover. This article goes into what differs between damage types — patching is patching, but cracks, delamination, worn hollows and oil contamination are not handled the same way.
General note: system-specific parameters for each Kadier coating system (coat thickness, curing time, chemical resistance) apply per the official manufacturer technical documentation when available. This article only gives a general process framework and does not replace that documentation. Standards TCVN 9014:2011 and TCVN 12574-2018 are used as general reference bases where relevant.
1. Classify the damage before patching
Do not size the patch area by feel, and do not patch before knowing how far the damage goes. Inspect visually, tap lightly to listen for hollow sounds in delaminated areas, and scrape a test edge to see whether the epoxy coat still bonds to the substrate or has fully separated.
- Hairline surface cracks: only the coating layer is cracked, the substrate below is intact. Usually handled by joint filling and localized recoating.
- Through-coat cracks, cracks following substrate joints: the crack runs deep or follows construction joints in the concrete. The substrate joint must be treated as well, not just the surface fill.
- Delamination, blistering: the coating has separated from the substrate, possibly due to substrate moisture or a weak substrate. The entire delaminated area must be cut out, and the moisture cause addressed before patching.
- Worn hollows, deep scratches forming ruts: common on forklift routes, forklift turning points and heavy rack feet. They need levelling before recoating, not just a new coat over the hollow.
- Oil or chemical contamination: the surface is discoloured, softened or will not bond to new coating. It must be cleaned and adhesion tested before coating, or the patch will delaminate together with the contaminated spot.
2. Patching process by damage type
2.1. Surface cracks: fill, then recoat
Widen the crack mouth slightly so the filler can bond, remove all dust, fill fully with a filler compatible with the coating system in use, wait for curing, grind flat, then recoat over the patched area, feathering a reasonable distance beyond the filler edge so the fill line does not show.
2.2. Through-coat cracks: treat the substrate joint first
Cut along the crack down to the concrete substrate, clean it, treat the substrate joint according to its type (expansion joints need elastic material, not rigid fill as for ordinary cracks), then fill, prime and recoat. Rigidly filling a joint that is still moving will reopen the crack in exactly the same place.
2.3. Delamination, blistering: cut out the entire damaged area
Mark out an area slightly wider than the visible delamination edge, cut out all separated coating, grind the substrate inside the patch area, check substrate moisture and treat moisture if needed, then rebuild the full coat system from primer to topcoat. Patching over a delaminated area without cutting it out will let the patch edge delaminate outward.
2.4. Worn hollows: level flat, then coat
Grind the worn area clean, level it with mortar or a suitable self-levelling layer (see LevelFlow — Self-Leveling for areas that need high flatness), wait for curing, grind flat, then recoat. Coating directly over a hollow only gives the hollow a new colour; it does not remove the hollow.
2.5. Oil contamination: clean, test adhesion, then coat
Remove oil by a suitable method, wash clean, let dry, grind a test area and check adhesion over a small area before coating widely. If the test coat still peels, that area needs deeper substrate treatment; do not try to hide it with a thick coat.
3. Recoating the patched area: joints and colour
The two most visible features of a patch are the joint line and colour mismatch. To limit them, feather the patch edge by abrasion instead of leaving a sharp edge, feather the topcoat outward gradually instead of stopping abruptly, and use the same coating system and colour code as the existing coat. Even then, a new patch may differ slightly in colour from a floor that has been in use for years — say this in advance to the operations team, especially in display areas and main walkways. For roller-applied systems, see RollCoat — 3-Coat Roller System; for areas needing anti-static protection, patching must preserve system continuity, see StatGuard — Anti-Static.
4. When spot repair is no longer enough
Move to recoating a whole zone or the full floor when: damaged areas are scattered across the floor, total damaged area is large relative to the zone, damage recurs at the same spot after every repair, or the substrate underneath is weak over a wide area. The principle is: patch while damage is still localized, recoat fully once damage has spread — the criteria for deciding on full recoating are the subject of a separate article in the same epoxy floor maintenance and repair category.
5. Acceptance of the patched area
Before returning the patched area to use: visually inspect the whole patch and its joint lines, check flatness in levelled areas, check adhesion by pull-off testing where the area has strict requirements (see Pull-Off Adhesion Testing for Epoxy Floors), and only allow vehicles through after the coating has cured sufficiently per the technical documentation of the system in use. Record the location, damage type, materials and patch date in the floor log so the next inspection has a basis for comparison.
6. Common patching mistakes
- Patching over delaminated coating without cutting out all separated areas.
- Rigidly filling an expansion joint that is still moving.
- Skipping the primer, coating directly onto freshly ground substrate or levelling mortar that has not cured.
- Using a different system or colour from the existing coat, then expecting the patch not to show.
- Letting forklifts run over the patch before the coating has cured sufficiently.
Frequently asked questions
Is spot repair as durable as full recoating?
If the substrate is still sound and the repair method matches the damage type, the patched area can be used normally. Durability drops when the wrong repair is used for the damage type or the substrate below is already weak.
Will the patched area show?
It usually remains visible on close inspection, especially a slight colour difference from the old floor. Feathered edges, feathered coating and the same system and colour code keep the patch as discreet as possible.
Should small cracks be patched without help?
Small, dry, non-spreading surface cracks can be handled simply, but through-coat cracks, delamination, blistering or oil contamination should be assessed by the installation contractor, because a wrong repair can let damage spread.
If your factory floor has many damaged spots at once or recurring damage, send a request through the epoxy floor coating quote page or contact Kadier for a survey and advice on the right patch-or-recoat option.
Illustration: Anna Tarazevich / Pexels (not a Kadier installation project).
