How to Prep Floors, Edges, Corners, and New Concrete Before Installing Epoxy Flooring
When it comes to epoxy flooring, the success of your installation depends on proper surface preparation. Customers often ask: Should I use shot blasting or diamond grinding? How do I handle corners and edges? What about new concrete patches or ramps? Let’s break it down.
Shot Blasting vs. Diamond Grinding
Both shot blasting and diamond grinding are excellent ways to prepare a concrete surface for epoxy coatings.
- Shot blasting uses steel shot to clean and profile the surface. It creates an aggressive texture and is especially effective for large, open areas.
- Diamond grinding uses rotating diamond segments to abrade the surface. It leaves a flatter profile and is a good option when you need precision or when shot blasting isn’t practical.
The choice often comes down to the size and condition of the floor. In many cases, contractors will use both methods—shot blasting for the main area, followed by grinding for touch-ups.
What About Corners and Edges?
No blaster or grinder reaches all the way into tight corners and along edges. That’s where hand tools come in.
- A wood floor edger or hand grinder can handle most edges.
- For stubborn corners, a scaler (an air hammer fitted with needle-like points) works especially well.
- In tough spots, even a sharp chisel can help remove weak or unsound concrete.
The good news: corners typically don’t see heavy traffic, so the goal is simply to make them sound and as well-prepared as possible.
Avoid Concrete Patches Under Epoxy
It’s tempting to repair ramps, height transitions, or cracks with regular concrete. But we don’t recommend it. Concrete patches are prone to cracking and loosening over time, creating voids beneath your epoxy system.
This risk is even greater in facilities dealing with chemical vapors—such as former dry-cleaning plants with PERC contamination—because trapped vapors can accelerate deterioration of weak patches.
The Better Solution: Epoxy Mortar
Instead of concrete, we recommend making repairs with an epoxy mortar. Mix Epoxy.com Product #12 Primer with silica sand to form a strong, durable patching compound. This bonds tightly to the existing slab and is fully compatible with your epoxy coating system.
This approach ensures your “ramp” or patch area blends seamlessly with the rest of the coated floor—and stays solid for years to come.
Understanding the 28-Day Rule
A common question is whether epoxy primers can be applied to freshly poured concrete. The answer: not yet.
The 28-day cure time is a requirement of the concrete itself, not the epoxy. The American Concrete Institute (ACI) sets this standard to ensure concrete reaches full strength before coatings are applied.
So, if you’re installing new concrete in part of your floor, coat the existing slab right away, but leave the new section until it has cured for 28 days. Then, come back with the same epoxy primer and coating system. The new section will blend in with the rest of the floor.
Key Takeaways
- Use shot blasting for aggressive profiling and diamond grinding for precision.
- Prep corners and edges with hand tools like grinders, scalers, or chisels.
- Avoid patching with concrete—use an epoxy mortar made from #12 primer and silica sand instead.
- Follow the 28-day cure rule for new concrete; it’s about the concrete, not the epoxy.
By following these guidelines, you’ll create a strong, continuous epoxy floor that resists chemical attack, handles traffic, and protects your concrete substrate for the long term.
For more detailed information
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Posted by Norm Lambert 
