The 5 Most Likely Reasons Your Epoxy Peeled Up

1. Moisture Vapor Pushing the Coating Off the Slab

Moisture is the #1 cause of large‑sheet delamination. If vapor pressure builds under the coating, it lifts the epoxy cleanly off the concrete — exactly like peeling vinyl flooring. Sources confirm moisture intrusion is a leading cause of peeling.

Signs this is the cause:

• Peeling starts near control joints or edges

• Bubbles or blisters before peeling

• Damp smell or dark spots in humid weather

• No vapor barrier under the slab (common in older garages)

2. Poor Surface Prep (Too Smooth, Dirty, or Contaminated Concrete)

If the concrete wasn’t mechanically profiled (diamond‑ground), the epoxy has nothing to grip. Even invisible contaminants — oils, silicone, cleaners — block adhesion. This is one of the top causes listed in all sources.

Signs this is the cause:

• The underside of the peeled epoxy looks smooth

• You see dust, paint, or old sealer still on the slab

• The concrete looks shiny instead of rough like 60–100 grit sandpaper

3. Applying Epoxy Over a Sealer or Old Coating Without Grinding

If the slab had:

• Cure‑and‑seal

• Acrylic sealer

• Old paint

• DIY epoxy …then the new epoxy bonded to the coating, not the concrete. When that weak layer lets go, the whole system peels up like linoleum.

4. Incorrect Mixing or Application Conditions

Improper mixing ratios, cold temperatures, or high humidity can prevent epoxy from curing correctly. Sources note that under‑mixed or improperly cured epoxy loses adhesion and peels.

Signs this is the cause:

• Soft or rubbery spots

• Glossy areas that never fully hardened

• Strong ammonia smell days later

5. No Primer or Wrong Primer

Primers are designed to soak into the concrete and create a chemical anchor. Skipping primer — or using the wrong one — increases the chance of sheet‑style delamination