Common Failures: Delamination, Bubbles, Fish-Eyes, Peeling, and How to Prevent Them

Failure Diagnostics: Start With a Simple Split

Most epoxy floor failures trace back to one of two buckets: (A) surface/bond issues or (B) mixing, application, and environment issues. Your first job is to classify the symptom correctly before you start grinding or recoating.

A. Surface/Bond Issues (Adhesion Problems)

• Failures that lift from the concrete (or lift in sheets) usually point to contamination, weak concrete, or an adhesion break between coats.
• Clues: coating releases cleanly from the slab; underside of coating looks dusty/dirty; concrete surface looks polished or chalky; failure follows tire paths, oil spots, or edges.

B. Mixing/Application/Environment Issues (Cure/Flow Problems)

• Failures that stay bonded but look ugly or feel wrong (bubbles, fish-eyes, roller marks, soft spots) usually point to viscosity, technique, temperature, or ratio errors.
• Clues: coating is stuck to the slab but has craters, pinholes, streaks, or rubbery areas; defects are uniform across the floor or match batch boundaries.

Fast Triage Checklist (What to Observe Before Touching Anything)

Delamination: Root Causes and Prevention

Delamination is loss of adhesion between coating and concrete or between coats. It can show up as peeling, flaking, or large sheets releasing.

Root Cause 1: Contamination (Bond Breakers)

Even small amounts of oil, silicone, tire dressing, curing compounds, or airborne shop contaminants can prevent wetting and adhesion. Delamination often starts in “hot spots” (parking bays, under compressors, near doors).

• Prevention: treat contamination as localized until proven otherwise; isolate and test suspect areas; keep silicone sprays, lubricants, and tire shine out of the space during coating.
• Diagnostic tip: if the underside of the peeled coating looks glossy or has a distinct dirt/oil pattern, suspect contamination.

Root Cause 2: Weak or Unsound Concrete (Cohesive Failure)

If the concrete surface is weak, the epoxy may bond to it but the concrete itself breaks. You’ll see concrete attached to the underside of the coating (the coating “wins,” the slab loses).

• Prevention: identify weak, chalky, or friable zones early; remove until sound substrate is reached; don’t “seal in” dust.
• Diagnostic tip: look for sand-like concrete on the back of delaminated pieces and a rough, torn slab surface.

Root Cause 3: Missed Recoat Window / Intercoat Adhesion Loss

If a coat cures past its recoat window, the next layer may not chemically bond. Without proper abrasion and cleaning, layers can separate under traffic.

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• Prevention: track recoat windows per product; if you miss it, mechanically abrade to a uniform scratch and remove dust before recoating.
• Diagnostic tip: delamination occurs between layers (primer/base or base/top), not at the concrete interface; you may be able to peel the top layer off leaving the lower coat intact.

Bubbles and Outgassing: Root Causes and Prevention

Bubbles can be trapped air, solvent pop (in some systems), or outgassing from concrete pores as the slab warms and expands.

Root Cause 1: Warming Slab (Classic Outgassing)

When concrete temperature rises after coating begins (morning sun on a slab, heaters turned on, doors opened to warm air), air in the pores expands and pushes into the wet film.

• Prevention: apply when slab temperature is stable or falling; avoid direct sunlight on the slab during application; keep doors closed if warm air will hit a cool slab and then warm it.
• Diagnostic tip: bubbles are worse in sun patches, near exterior doors, or in areas that warm first.

Root Cause 2: Coats Too Thick (Film Skins Over)

Thick coats can “skin” on top while gases are still trying to escape, locking bubbles in place.

• Prevention: follow spread rates; don’t try to make one coat do the job of two; keep consistent squeegee pressure and backroll timing.
• Diagnostic tip: bubbles cluster in puddles, low spots, or along pour ribbons where material sat thick.

Root Cause 3: Aggressive Rolling or Overworking

Fast rolling, dry rolling, or repeatedly going back over tacky material can whip air into the coating.

• Prevention: maintain a wet edge; use the correct roller cover and loading; stop backrolling once the film starts to set.

Fish-Eyes (Cratering): Root Causes and Prevention

Fish-eyes are circular craters where the coating pulls away from a spot, usually due to low-surface-tension contaminants like silicone or oil. They can also come from airborne contamination settling into wet epoxy.

Root Cause 1: Silicone/Oil on the Surface

• Prevention: keep silicone-based products out of the space; avoid using contaminated rags, mop heads, or buckets; isolate detailing products (tire shine, spray lubricants) far from the job.
• Diagnostic tip: fish-eyes often appear quickly after rolling and may be concentrated near workbenches, garage door tracks, or areas where sprays are used.

Root Cause 2: Contaminated Tools or Airborne Overspray

• Prevention: use dedicated, clean rollers and mixing tools; don’t run aerosol lubricants, WD-type sprays, or silicone caulks in the same airspace during coating.
• Diagnostic tip: fish-eyes appear in a pattern that matches where you set tools, staged materials, or where airflow carried contaminants.

Roller Marks and Texture Lines: Root Causes and Prevention

Roller marks are visible lap lines, stipple differences, or ridges that remain after cure. They’re usually a flow/leveling problem, not an adhesion problem.

Root Cause 1: Viscosity Too High (Cold Material or Late Pot Life)

As epoxy warms/cools and as pot life advances, viscosity changes. Thickening material won’t level, so roller texture freezes in.

• Prevention: stage batches so you’re not rolling near end-of-pot-life; keep material at recommended temperature; pour out promptly rather than letting it build heat in the bucket.
• Diagnostic tip: marks worsen toward the end of a batch or in areas rolled last.

Root Cause 2: Technique (Dry Rolling, Poor Overlap, Wrong Roller)

• Prevention: keep roller loaded; use consistent overlap; backroll in one direction for uniform texture; use the roller nap recommended for the product and floor profile.
• Diagnostic tip: lines follow roller width and overlap rhythm; edges/cut-ins may look different than the field.

Soft Spots, Tacky Areas, and Poor Cure: Root Causes and Prevention

Soft spots are areas that remain rubbery, tacky, or easily gouged after the rest of the floor cures. This is most often a mixing/ratio or batch handling problem.

Root Cause 1: Ratio Errors (Off-Ratio Mix)

If Part A and Part B aren’t proportioned correctly, the polymer network can’t form properly. The result is under-cured epoxy that may never fully harden.

• Prevention: use marked containers or calibrated measuring; never “eyeball” partial mixes; keep consistent batch sizes.
• Diagnostic tip: soft zones align with a specific batch boundary, a cut-in mix, or a “small touch-up” mix.

Root Cause 2: Incomplete Mixing (Unmixed Material on Sides/Bottom)

• Prevention: scrape sides and bottom during mixing; consider a two-container transfer mix method for critical coats (mix, transfer, mix again) when allowed by product instructions.
• Diagnostic tip: sticky streaks or swirls; soft areas shaped like where you dumped the bucket or where you cut in.

Root Cause 3: Temperature-Related Cure Slowdown (Not a Ratio Error)

Cool conditions can make epoxy feel soft longer. The key difference: it should steadily improve with time and warmth, not remain permanently gummy.

• Diagnostic tip: entire floor is slow, not isolated patches; hardness improves day by day.

Repair Playbook: Step-by-Step From Assessment to Recoat

Repairs fail when you treat symptoms cosmetically. Use this sequence to decide whether you need a spot repair, a section rework, or a full recoat.

Step 1: Identify the Extent (Map It)

• Mark all defects with tape or marker: delamination edges, bubble fields, fish-eye clusters, soft spots.
• Tap test for hollow areas (coin or small hammer) and outline the “drummy” zones.
• Decide if the issue is localized (one bay) or systemic (entire floor or entire batch).

Step 2: Determine Failure Plane (Where Did It Let Go?)

• Concrete interface failure: coating releases from slab → focus on contamination/weak concrete and re-profile.
• Intercoat failure: top layer peels off lower layer → focus on missed recoat window or surface between coats.
• Cure defect without delamination: bubbles/roller marks/fish-eyes but bonded → focus on sanding and recoat strategy.

Step 3: Mechanical Removal (No Shortcuts)

Remove all compromised material until you reach sound, well-bonded coating or sound concrete.

• For delamination: grind beyond the visible edge into firmly bonded material to avoid a weak “lip.”
• For soft spots: remove all under-cured epoxy completely; do not coat over tacky material.
• For bubbles/fish-eyes/roller marks: sand or grind to remove craters/ridges and create a uniform mechanical tooth for the next coat.

Step 4: Re-Profile the Repair Area

• Feathering to a razor edge is unreliable. Aim for a tapered transition with enough surface texture for the next coat to grip.
• If the surrounding coating is glossy or beyond recoat window, abrade it to a uniform scratch pattern where the new coat will overlap.

Step 5: Clean the Area (After Grinding)

• Vacuum thoroughly; dust left behind becomes a bond breaker.
• Use the manufacturer-approved wipe/clean method for the system; change rags frequently so you don’t smear contaminants back on.

Step 6: Spot Prime (When Needed)

Spot priming helps seal exposed concrete and equalize absorption so your patch doesn’t “sink in” or flash differently.

• Prime bare concrete areas and any porous repair mortar zones.
• Keep primer within the sanded/abraded boundary so you don’t create a glossy halo that could telegraph through.

Step 7: Patch/Build and Respect Feathering Limitations

• Feathering limitation: thin edges tend to show as a witness line and can chip under traffic. Plan to overlap with a full coat when appearance matters.
• For small cosmetic defects (light roller marks or minor bubbles): sand smooth and apply a thin recoat over a wider area to blend.
• For fish-eyes: remove the cratered film and address contamination source; otherwise the defect can repeat in the recoat.

Step 8: Choose a Recoat Strategy

Practical Mini-Workflows (Examples You Can Follow)

Example 1: Peeling in One Parking Bay

1. Outline peeling and hollow zones; scrape-test the edge to see if it releases from concrete.
2. Grind until you reach sound concrete (or sound bonded coating) plus a margin beyond the edge.
3. Re-profile the exposed slab; vacuum and clean.
4. Spot prime exposed concrete; allow proper cure.
5. Rebuild coats in the bay, then apply a wider blend coat or full topcoat to avoid a visible patch boundary.

Example 2: Bubbles Concentrated Near the Garage Door

1. Confirm pattern matches warming/sun exposure and thicker ribbons.
2. Sand/grind to remove bubble peaks and open pinholes; vacuum.
3. Recoat when slab temperature is stable or falling; avoid thick puddles and keep spread rate consistent.
4. If pinholes remain after sanding, plan a sealing coat before the final finish coat.

Example 3: Soft Cut-In Strip Along One Wall

1. Press with a fingernail and compare to cured field; if it stays gummy, treat as under-cured.
2. Remove the soft strip completely (scrape/grind) until only hard, well-bonded material remains.
3. Clean thoroughly; rebuild with correctly measured, thoroughly mixed small batch.
4. Overlap into abraded surrounding area; consider a full-wall-to-wall recoat if the sheen difference is unacceptable.

Documentation System: How to Pinpoint Causes on Future Projects

When a failure happens, the fastest way to prevent repeats is to document conditions and batch details so you can correlate defects with time, temperature, and material handling.

What to Record (Minimum Viable Job Log)

• Project map: sketch the floor and label sections (Bay A, Bay B, etc.). Mark where each batch was poured and rolled.
• Product details: manufacturer, product name, part numbers, and lot/batch numbers from containers.
• Mix details: batch size, exact ratio method (full kit vs measured partial), mix time, whether you did a transfer mix, start/finish times.
• Application details: spread rate targets, tools used (squeegee notch, roller nap), number of workers, and sequence.
• Environmental snapshot: slab temperature, air temperature, relative humidity, and whether sun/heaters/doors changed conditions during the coat.
• Recoat timing: time between coats and whether abrasion was done (and with what grit/tool) if outside window.

How to Use the Log to Diagnose

• If defects align with a specific batch boundary on your map, suspect mixing/ratio/pot life handling.
• If defects align with sun patches, door openings, or heater cycles, suspect outgassing or viscosity/leveling changes.
• If defects align with known contamination zones (parking, equipment area), suspect bond breakers and target removal/containment.

Simple Template You Can Copy

JOB LOG (Epoxy Floor)  Date: ____  Address: ____  Crew: ____  Substrate: ____  Area: ____ sq ft  Product System: ____  Lot #: ____  Primer/Base/Top: ____  Batch Size: ____  Mix Start/End: ____  Pour Time: ____  Roll Time: ____  Slab Temp: ____  Air Temp: ____  RH: ____  Notes (sun/heaters/doors): ____  Defects Observed (location + time): ____