Key Takeaways
- Bad prep, not bad product, causes nearly every premature coating failure.
- Acid etching is not enough on most garage concrete. Mechanical grinding or shot blasting is the modern standard.
- Moisture testing is non-negotiable. Skip it and you’ll watch the coating bubble within months.
1. Acid Etching Instead of Grinding
Muriatic acid opens the very top layer of concrete, but it can’t reach previously sealed or polished slabs, and it can’t profile to the CSP 2 to 3 most resin systems need. Diamond grind every garage floor unless the contractor specifically certifies acid etching for the product in use.
2. Skipping Moisture Testing
Concrete wicks moisture up from the soil. A 12-hour plastic sheet test or a calcium chloride test is free and tells you if you need a moisture-vapor primer. Skip it and the coating delaminates inside a year.
3. Ignoring Cracks and Spalling
Coating over open cracks just telegraphs them through the finish in 6 to 12 months. Chase cracks, fill with a flexible polyurea crack filler, then grind flush before primer.
4. Not Vacuuming After Grinding
Grinding leaves micro-dust that kills adhesion. Pass with a HEPA vacuum, then a tack rag, then a final vacuum. If a wet rag picks up gray powder, vacuum again.
5. Wrong Mix Ratio
100% solids epoxy is unforgiving on mix ratio. Off by 5 percent and the floor stays soft. Use the kit’s volume markings, not eyeballs, and stir for the full time the data sheet calls for, scraping sides and bottom.
6. Bad Flash Times Between Coats
Recoating too early traps solvent and uncured resin. Recoating too late breaks the chemical bond and creates a mechanical bond only. Both shorten lifespan. Follow the product data sheet (PDS) for the temperature you’re installing at.
7. Installing Outside Temperature Limits
Most epoxy systems specify a 50 to 90 F slab temperature, not air temperature. The slab can be 10 to 20 degrees colder than the air on a sunny day. An infrared thermometer takes the guesswork out.
Quick Prep Checklist
- Test for moisture (12-hour plastic sheet or calcium chloride).
- Grind to CSP 2 or 3 (or shot blast).
- Repair cracks and pitting; grind flush.
- Vacuum, tack, vacuum.
- Check slab temp with IR thermometer.
- Mix by ratio, stir full time, scrape sides.
- Watch flash times to the PDS.
FAQs
How rough should the concrete be after grinding? A CSP 2 (light grit sandpaper feel) is fine for most 100% solids systems. Polyaspartic-only direct-to-concrete systems often want CSP 3.
Do I need a primer? If your concrete tested high for moisture, or it’s old, dusty, or oil-contaminated after grind, yes. Otherwise the basecoat doubles as primer.
Can I install in winter? Yes, with heated buildings, slab warming mats, or polyaspartic chemistry rated for low temperature.
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