What Kind of Preparation Is Required for an Existing Concrete Floor Before Coating?

Concrete coatings—whether epoxy, polyurea, or polyaspartic—can completely transform your garage, basement, or patio. But here's something most homeowners don't realize: the key to a long-lasting, professional-quality floor isn’t just the product—it’s the prep work.

Even the highest-quality coating can fail if the concrete surface isn't adequately prepared.

In this post, we’ll walk you through the steps involved in preparing an existing concrete floor before applying any coating. Whether you're researching before hiring a pro or just curious about the process, here’s what you need to know.

Step 1: Cleaning the Concrete

Preparation starts with a deep clean to remove:

• Dirt and dust

• Oil or grease stains

• Paint or adhesive residue

• Any existing sealers or coatings

How it’s done:

• Sweeping and vacuuming the surface

• Degreasing with commercial cleaners or etching agents

• Pressure washing (if applicable)

Why it matters: A coating needs to bond directly to clean concrete. Oil, moisture, or dirt can prevent adhesion, leading to peeling or bubbling later on.a

Step 2: Moisture Testing

Concrete may look dry—but it can hold moisture below the surface. Excess moisture is one of the biggest reasons coatings fail.

How it’s done:

• Plastic sheet test (taping plastic to the floor for 24 hours to check for condensation)

• Moisture meters or calcium chloride tests for more precise readings

Why it matters: Moisture can break the bond between the coating and concrete, causing blistering or delamination. If a moisture barrier is needed, it must be addressed before coating.

Step 3: Repairing Cracks & Imperfections

Coatings will highlight every flaw in the concrete if not corrected first.

Typical repairs include:

• Filling cracks, pitting, or spalling

• Patching holes or surface damage

• Leveling uneven spots or transitions

Materials used:

• Epoxy crack fillers

• Concrete patch compounds

• Self-leveling underlayments (if needed)

Why it matters: Coating over damaged or uneven concrete won’t just look bad—it could also lead to premature wear or trip hazards.

Step 4: Mechanical Surface Profiling

This is the most critical step—and the one that separates DIY jobs from professional-grade results. The goal is to open the pores of the concrete so the coating can soak in and create a strong chemical bond.

Methods include:

• Diamond grinding – Most common and effective

• Shot blasting – Used for heavy-duty prep or large industrial areas

• Etching (acid wash) – Sometimes used for DIY epoxy kits, but less effective than grinding

Why it matters: A properly profiled surface ensures maximum adhesion, durability, and longevity of your coating.