Epoxy Surface Preparation Guide

Proper surface preparation is the single most important step in installing any epoxy resin system. You can choose the best product in the world, mix it perfectly, and still have a failure if the surface is not prepared correctly. This page gives you a practical, field-tested guide to epoxy surface preparation so that your epoxy floors, walls, tanks, and secondary containment systems have the best chance of long-term success.

Use this guide any time you are wondering how to prepare concrete for epoxy, whether you are installing a light-duty coating, a mid-range chemical-resistant system, or a Novolac system for extreme exposure. Always read the product-specific technical data sheet in addition to this general information.

1. Start with a Sound Substrate

Epoxy is not a band-aid. It will not turn weak, crumbling, or contaminated concrete into a good floor. Before you think about coatings, make sure the substrate is:

Structurally sound – no loose, punky, or scaling concrete.
Dry. Many of our products are moisture tolerant, but a damp surface interferes with the penetration of the epoxy.
Free of heavy oil, grease, or contamination that can migrate back to the surface.

If the concrete is badly deteriorated or contaminated all the way through, you may need to remove and replace it, or install a resurfacing system designed for that purpose before you apply any coating.

2. Cleaning and Degreasing

Most problem jobs start with contamination. Epoxy likes clean, dry, porous concrete. Anything that sits between the concrete and the coating – oil, grease, curing compounds, old sealers, tire residues, or cleaning chemicals – can cause peeling or bonding loss.

For contaminated slabs:

Use an appropriate degreaser or cleaner to break down oils and grease.
Scrub with mechanical agitation (floor machine, stiff brooms, or brushes) – not just a mop.
Rinse thoroughly and remove the dirty water. Do not leave soaps or cleaners on the surface.
Allow the floor to dry completely before moving on to mechanical preparation.

If there is a previous sealer, paint, or unknown coating, plan on removing it rather than trying to coat over it. Epoxy bonds best to clean, profiled concrete – not to questionable old material.

3. Mechanical Surface Preparation

For most epoxy floor systems, the preferred method of surface prep is mechanical. The goal is to create a clean, sound surface with a profile similar to medium sandpaper – often described in the industry as the proper Concrete Surface Profile (CSP).

Common methods include:

Shotblasting – the best choice for many industrial floors. Provides a uniform, controllable profile.
Diamond grinding – useful where shotblasting is not practical, or for edging and detail work.
Scarifying or scabbling – used for heavy removal or very rough concrete that needs to be re-profiled.

Whichever method you choose, remove all dust and loose material afterward by vacuuming with an industrial vacuum equipped with proper filtration. Sweeping alone is not enough for good epoxy adhesion.

4. Moisture, Vapor, and pH Considerations

Moisture is another common cause of epoxy problems. Even a well-prepared surface can fail if there is excessive moisture vapor pressure coming up through the slab.

Before installing any epoxy floor coating:

Check for obvious signs of moisture – dark, damp areas, efflorescence, or a white powder on the surface.
If needed, perform a moisture test that is appropriate for your project and local standards.
Make sure there is no active hydrostatic pressure or free water coming through the slab.

Extremely high pH from moisture intrusion can also attack some coatings over time. If you suspect moisture problems, ask Technical Support for recommendations on moisture-tolerant primers and systems designed for those conditions.

5. Crack Repair, Joints, and Patching

Once the surface is clean and profiled, repair any defects before coating:

Cracks – rout or chase cracks as needed and fill with an appropriate resin or patching material.
Spalls and holes – repair with epoxy mortar or other recommended patching systems.
Joints – honor moving joints; do not bridge active expansion joints with rigid epoxy.

Repairs should be cured, ground flush, and prepared with the same surface profile as the surrounding concrete. This keeps the coating thickness even and reduces “picture framing” around patches.

6. Final Cleaning Before Priming

After mechanical prep and repairs, perform a final cleaning step:

Vacuum thoroughly to remove dust and fines from the surface and joints.
Inspect under good light – the surface should look uniform, clean, and lightly textured.
Remove any remaining debris, tape, or masking that might interfere with rolling or squeegeeing.

At this stage, the floor should be ready for primer. Avoid walking on the surface with dirty boots or tracking oil back onto the slab. Treat it like a finished surface from this point forward.

7. Environmental Conditions for Installation

Even with perfect surface preparation, poor conditions can ruin a job. Before mixing epoxy:

Verify that substrate, air, and material temperatures are all within the recommended range.
Check that relative humidity and dew point are suitable so that condensation will not form on the surface.
Protect the area from sudden temperature swings, drafts, and exposure to moisture during cure.

Each epoxy system has specific temperature and recoat window requirements. Always follow the product’s technical data sheet for mixing, application, and cure schedules.

8. Basic Checklist – Is the Surface Ready for Epoxy?

Before you open Part A and Part B, ask yourself:

Is the concrete structurally sound and free of loose material?
Has all oil, grease, curing compound, sealer, and old paint been removed?
Does the slab have a clean mechanical profile suitable for epoxy?
Are moisture and vapor conditions acceptable for the system you plan to install?
Have cracks, spalls, and joints been properly treated?
Is the surface clean, dry, and dust-free?
Are temperature and humidity within the limits for your product?

If you can answer “yes” to all of these, you are ready to move on to the epoxy installation guide for the specific system you are using.

9. When in Doubt, Ask

Every job is a little different. If your project involves unusual chemicals, heavy thermal shock, extreme abuse, or concrete in poor condition, please contact Technical Support before you start. It is much easier to adjust the system before installation than to repair a failed floor later.