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Epoxy Over Urethane: Techniques and Tips for a Flawless Finish


When it comes to achieving a flawless finish with epoxy over urethane, understanding the right techniques and tips is crucial. This article will guide you through everything you need to know to ensure a durable and beautiful result.

Before we dive deep, here’s a quick summary for those looking for fast answers:

  • Epoxy can be applied over urethane, but surface preparation is key.
  • Surface must be cleaned and roughened (usually with 100-grit sandpaper) to ensure proper adhesion.
  • Avoid using epoxy over water-based polyurethane directly; it’s better to use oil-based polyurethane.

In this guide, we will explore:

  • The properties and applications of both epoxy and urethane.
  • Step-by-step instructions for surface preparation and the application process.
  • Tips to achieve a smooth, bubble-free finish.
  • Solutions to common issues like wrinkling and fisheye blemishes.

By the end, you’ll be well-equipped with the knowledge to handle any epoxy over urethane project confidently.

Benefits of Epoxy Over Urethane - epoxy over urethane infographic brainstorm-6-items

Understanding Epoxy and Urethane

When it comes to flooring, both epoxy and urethane have their unique properties and applications. Understanding these differences is crucial for achieving a durable and flawless finish.


Epoxy is a thermosetting polymer known for its high strength and excellent adhesion to concrete surfaces. It forms a hard, durable coating that is resistant to chemicals, abrasion, and impact. Epoxy is also highly customizable, available in a variety of colors and finishes.

Urethane, on the other hand, is a versatile polymer that can be either thermosetting or thermoplastic. It offers excellent flexibility and UV resistance, making it less likely to yellow or degrade when exposed to sunlight. Urethane is also resistant to abrasion and chemicals, though it is generally softer and more flexible than epoxy.


One key difference between the two is how they bond to surfaces. Epoxy bonds exceptionally well to concrete, creating a strong base layer. Urethane, however, does not bond as well to concrete but adheres perfectly to epoxy. This makes the combination of epoxy and urethane an ideal solution for industrial flooring.

Another difference is their reaction to UV light. Epoxy can yellow over time when exposed to sunlight, while urethane is more UV-resistant, maintaining its appearance longer.


Epoxy is commonly used in industrial settings where a tough, durable surface is required. It’s ideal for warehouses, factories, and garages. Its quick curing time and robust chemical resistance make it a popular choice in these environments.

Urethane is often used as a topcoat over epoxy in areas that require UV resistance and flexibility. It’s excellent for environments exposed to sunlight or requiring a softer, more flexible coating, such as gym floors or outdoor patios.

UV Resistance

As mentioned, epoxy is not UV-resistant and can yellow over time. This is where urethane comes into play. Applying a urethane topcoat over an epoxy layer provides the best of both worlds: the durability and adhesion of epoxy with the UV resistance and flexibility of urethane.


Both materials are durable, but they excel in different areas. Epoxy offers superior hardness and impact resistance, making it suitable for heavy-duty applications. Urethane, while slightly less hard, provides excellent abrasion resistance and flexibility, making it ideal for areas with foot traffic or where the floor might need to flex.

Combining these two creates a flooring solution that is both hard and flexible, resistant to both chemical spills and UV light, and capable of withstanding heavy use for years.

Next, we’ll dive into how to prepare the surface for applying epoxy over urethane to ensure a strong, lasting bond.

Preparing the Surface for Epoxy Over Urethane

Cleaning and Sanding

Before applying epoxy over urethane, proper surface preparation is crucial. Start by thoroughly cleaning the surface. Remove any dust, dirt, and grease using a mild detergent and water. Rinse well and let it dry completely.

Next, you’ll need to sand the urethane-coated surface to create a texture that the epoxy can grip. Use 100-grit sandpaper for this step. Sand the entire surface evenly, paying special attention to any glossy areas, as epoxy needs a rough surface to adhere properly.

For hard-to-reach areas or intricate details, a Scotch-Brite pad can be very effective. These pads are less aggressive than sandpaper but still provide enough abrasion to help with adhesion.

After sanding, remove all dust and debris. You can use a vacuum, followed by a tack cloth to ensure the surface is completely clean. Any remaining dust can interfere with the bonding process, leading to an uneven finish.

Creating a Mechanical Bond

Creating a mechanical bond is essential for a durable finish. After sanding, you need to create a microtexture that the epoxy can latch onto. This involves lightly scuffing the surface to achieve a uniform matt finish.

Use a cushioned sanding block and 320-grit abrasive paper for this step. The goal is not to remove the urethane but to create tiny grooves that will help the epoxy adhere better.

Here’s a step-by-step process to follow:

  1. Lightly Sand: Use the 320-grit abrasive paper to lightly sand the surface. Aim for a uniform matt finish.
  2. Clean Again: Remove all sanding dust using a vacuum and a tack cloth. Ideally, do this in a separate room to avoid airborne dust settling back onto the surface.
  3. Inspect: Ensure the surface is uniformly scuffed and free from any glossy patches.

This preparation ensures a strong mechanical bond, making the epoxy application smoother and more durable.

Next, we’ll guide you through the actual process of applying epoxy over urethane.

Applying Epoxy Over Urethane

Step-by-Step Application Process

  1. Gather Materials: You’ll need epoxy resin, a mixing container, a stir stick, a brush or roller, and protective gear (gloves and goggles).

  2. Mix the Epoxy: Follow the manufacturer’s instructions for mixing the epoxy resin and hardener. Mix thoroughly to avoid any unmixed portions that could cause curing issues.

  3. Apply the First Epoxy Layer: Pour a thin layer of epoxy over the prepared urethane surface. Use a brush or roller to spread it evenly. Work quickly but carefully to avoid bubbles.

  4. Curing Time: Allow the first layer to cure according to the manufacturer’s guidelines. This usually ranges from 24 to 48 hours. Maintain a stable temperature and humidity level during this period to ensure proper curing.

  5. Inspect the First Layer: After the first layer is cured, check for any imperfections. Lightly sand any rough spots and clean the surface again to remove dust.

  6. Apply Additional Layers: If needed, apply additional layers of epoxy. Each layer should be thin to prevent sagging or pooling. Allow each layer to cure fully before applying the next.

  7. Final Curing: Once all layers are applied, let the final layer cure completely. This can take several days, depending on the epoxy brand and environmental conditions.

Tips for a Flawless Finish

  1. Smooth Application: Use a high-quality brush or roller to apply the epoxy smoothly. This helps to avoid streaks and uneven surfaces.

  2. Avoiding Bubbles: To prevent bubbles, mix the epoxy slowly and thoroughly. Apply the epoxy in thin layers and use a heat gun or torch to gently remove any bubbles that appear.

  3. Leveling: Ensure the surface is level before applying the epoxy. This helps the epoxy to spread evenly and reduces the risk of pooling.

  4. Edge Control: Use painter’s tape around the edges of the surface to control the flow of epoxy. This prevents drips and ensures clean edges.

  5. Temperature and Humidity: Maintain a stable temperature (around 70-75°F) and low humidity during the application and curing process. Fluctuations can affect the curing time and final finish.

  6. Patience: Allow each layer to cure fully before adding another. Rushing the process can lead to imperfections and weaker bonding.

By following these steps and tips, you can achieve a durable and beautiful epoxy finish over urethane. Next, we’ll cover common issues you might encounter and how to solve them.

Common Issues and Solutions

Troubleshooting Adhesion Problems

When applying epoxy over urethane, adhesion problems can arise. This is often due to the epoxy not bonding well with the urethane surface. Here are some key steps to troubleshoot and fix these issues:

  1. Identify the Type of Urethane: Epoxy does not bond well to water-based polyurethane. To fix this, apply 2-3 coats of oil-based polyurethane over the water-based layer. This creates a better surface for the epoxy to adhere to.

  2. Test Areas: Before applying epoxy to the entire surface, test it on a small area. This helps identify any potential problems with adhesion or compatibility.

  3. Multiple Coats: If you notice that the epoxy is not sticking well, consider applying multiple coats of oil-based polyurethane. This can improve the bonding surface.

Preventing and Fixing Blemishes

Blemishes such as wrinkling, softening, and fisheye marks can spoil your finish. Here’s how to prevent and fix these issues:

  1. Wrinkling and Softening: These issues can occur if the epoxy reacts with the underlying urethane. To avoid this, ensure that the urethane is fully cured before applying the epoxy.

  2. Fisheye Blemishes: These are caused by surface tension differences, often due to contamination. Clean the surface thoroughly before applying epoxy. Use solvents like isopropyl alcohol to remove any oils or residues.

  3. Proper Mixing: Improper mixing of the epoxy can lead to bubbles and other imperfections. Follow the manufacturer’s instructions for mixing ratios and techniques. Mix slowly to avoid introducing air bubbles.

  4. Application Techniques: Use a foam brush or roller for a smooth application. Pour the epoxy in a thin, even layer and use a heat gun or torch to remove any bubbles that form.

  5. Surface Tension: To prevent fisheye blemishes, ensure the surface is uniformly scuffed. A light sanding with 320-grit abrasive or Scotch-Brite can create the necessary microtexture for a strong mechanical bond.

By addressing these common issues, you can achieve a flawless epoxy finish over urethane. In the next section, we’ll answer some frequently asked questions about this process.

Frequently Asked Questions about Epoxy Over Urethane

Can you put epoxy over urethane?

Yes, you can put epoxy over urethane, but it’s not always straightforward. Proper surface preparation is crucial for a strong bond.

Epoxy and urethane have different chemical properties. Epoxy bonds well to many surfaces, but urethane can act as a barrier. To ensure a good bond, you need to create a mechanical bond by scuffing the urethane surface. Lightly sanding with a 320-grit abrasive or using Scotch-Brite can help. This creates a microtexture that the epoxy can grip onto.

Can I use polyurethane to seal wood before epoxy?

Using polyurethane to seal wood before epoxy is possible, but it comes with risks. Polyurethane can protect the wood and prevent off-gassing, which can cause bubbles in the epoxy. However, epoxy doesn’t bond well to polyurethane, which can lead to adhesion problems.

Oil-based polyurethane is better than water-based for this purpose. Water-based polyurethane can wrinkle or soften when epoxy is applied over it, leading to blemishes like fisheyes. If you choose to seal wood with polyurethane, apply 2-3 coats of oil-based polyurethane and test on a small area first.

Does epoxy stick to urethane rubber?

Epoxy does not bond well to urethane rubber. Urethane rubber is flexible and can interfere with the bonding process. Epoxy is rigid, and the flexibility of urethane rubber can cause the epoxy to crack or peel off.

For applications requiring both materials, consider using them in layers rather than mixing. Apply epoxy first, then urethane rubber over the cured epoxy. This approach leverages the strengths of both materials without compromising the bond.

By understanding these nuances, you can make informed decisions for your projects involving epoxy and urethane. Let’s dive into some common issues and solutions in the next section.


At Rubcorp, we are committed to providing premium solutions for all your surfacing needs. Whether you’re working with epoxy, urethane, or a combination of both, our expert training and support ensure you get the best results every time.

Our mission is to serve our installation and distribution partners with industry-leading products and services. We offer comprehensive training events, like the ones scheduled throughout 2024, to help you master the techniques of applying epoxy over urethane and other advanced surfacing methods.

Why Choose Rubcorp?

  • Industry-Leading Training: Our training sessions are designed to equip you with the skills and knowledge needed to achieve a flawless finish. From surface preparation to final application, we cover every detail.
  • Premium Products: We supply only the highest quality components at the best prices, ensuring your projects stand the test of time.
  • Unmatched Support: Our global support network is always ready to assist you, whether you’re facing a technical challenge or need advice on the best products for your specific needs.

Case Study:
Brian and his team at Rubcorp have supported numerous projects, including those exceeding 500,000 square feet in rubber surfacing. Their expertise and dedication have made them a trusted partner in the industry.

By choosing Rubcorp, you’re not just getting top-tier products; you’re gaining a partner dedicated to your success. For more information on how epoxy and urethane can transform your projects, visit our polyurethane vs epoxy page.

Ready to elevate your surfacing projects? Contact us today to learn more about our premium solutions and training programs.

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Creative Director, Rubcorp Distribution, LLC

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