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Two questions that we are often asked is how to recoat or apply a new coat of epoxy to an older epoxy floor that has already cured and can you apply a clear coat to an older epoxy garage floor coating? If you’ve done a little bit of research on epoxy application, then you know how important floor preparation is. So let’s discuss how to determine if your floor qualifies for a recoat and then how to prep the floor before you do.
When can you apply epoxy over an older coating?
There are many examples of when you can apply a new coat of epoxy over an older cured coating. The most common of these are for people who had previously applied a color coat and now realize that they want the glossy looks and advantages of adding a clear coat.
Sometimes it’s as simple as someone who planned a multiple coat flooring system and waited too long between coats, allowing the epoxy to cure, before applying the next coat in order to get a chemical bond.
Another reason is to renew the clear top coat. After many years of service in a busy garage, the clear top coat of an epoxy floor can start to show its age. With the proper floor preparation, you can add another coat of clear and make the floor look brand new again.
And then finally, you may have an older existing coating that is showing wear from years of heavy traffic and getting thin. As long as the floor is not experiencing any delamination issues, many times you can recoat right over a worn epoxy floor to create a brand new looking finish.
As long as the existing garage floor coating is a 2-part resinous product such as epoxy, polyurea, polyaspartic, or polyurethane, then you should be able to apply an additional coat of a compatible product without issue. However, to be safe you should always consult with the manufacturer of the new coating first.
When not to apply epoxy over an older coat
If the existing epoxy floor coating is peeling up or showing other signs of delamination, then you do not want to epoxy over it. There are bigger issues at play here that are causing the delamination. Applying a new coat of epoxy over such a coating will only lead to more problems. A complete removal of the old coating by grinding would be required.
If the coating is fairly worn with more concrete showing through than there is epoxy, then you will want to start fresh by grinding the floor.
Do not attempt to apply epoxy over existing concrete sealers. These need to be removed first as epoxy will not adhere to them. Also, floor paint is not a good base for epoxy and needs to be removed as well.
How to prep epoxy for another coat
The key to applying a new coat is to mechanically rough up the surface of the older coat to create enough bite for the epoxy to adhere to it. There are a couple of ways to achieve this.
The first is to use 120 grit sandpaper on an orbital sander or pole sander like this one at Amazon
. What you are trying to do is rough up the surface, not remove it. The surface should look deglossed after sanding.
Once done, sweep up the heavy stuff and then vacuum the entire floor with a shop vac. Next, use denatured alcohol on a small towel and wipe down the entire surface. The denatured alcohol will remove all the fine dust particles, evaporate quickly, and make sure that the surface is clean.
The other option is to use a floor maintainer (buffer) with a 100 grit sanding screen. You can usually rent these fairly inexpensively from your local home improvement center. They should have the sanding screens to purchase as well.
This method will go faster than the pole sander and cover a lot of floor quickly if you have quite a bit of square feet to prep. Just remember to occasionally check the sanding screen for wear and to make sure it hasn’t clogged up. After you are done, vacuum the floor and use denatured alcohol as described with the sanding method.
If you have an older clear coat that you want to renew, then you will want to use 80 – 100 grit sandpaper or a 60 – 80 grit sanding screen first to actually remove a small layer of the coating. This will help to eliminate any deeper scratches and/or embedded dirt that has marred the finish.
Do the same if you have a worn coating that is adhered very well but has some spots where the coating has worn through to the concrete. The more aggressive grit will insure that the bare concrete will be prepped properly as well.
Floor prep such as this goes fairly quickly. Once you wipe down the floor with the denatured alcohol, your floor is ready for a new coat of epoxy or floor coating of your choice.
Hi…we coated our garage floor about six years ago. I’m 99% sure we used the professional grade rustoleum epoxy kit with flakes and a clear gloss top coat. It has adhered beautifully. The only issue we had was yellowing the first few feet from the door. Unfortunately, someone in the house thought the yellowing was dirt and used a cleaner that seems to have stripped the coating or something. So now we have areas that are very white, almost look bleached out. When you rub the white areas with a damp cloth you can see the color and flakes below but then it dries white again. From your article and the comments I’m thinking we need to sand with 80-100 grit then re do the gloss. Is that correct or is their something else we can try? Or will that not work? If we need to reapply the gloss should we stick with the rustoleum? Thank you.
Hi Matt. You are correct regarding yellowing of epoxy. It sounds like someone used an acidic based product in combination with a course scrub pad. 120 grit sandpaper works fine for a recoat. You can use 80-100 if there are areas in the floor that have some ground-in dirt or scratches you want to remove. The entire floor will look hazy, but once you apply the new clear coat all the clear gloss will come back. If the Rust-Oleum has performed well up to this point, then you will be fine using that again. If you want something that even better abrasion ratings (longer wear) and that is U.V. stable (will not amber/yellow), then you can apply a high performance polyurethane or single-part polyurea clear coat. We have links in the article to vendors we recommend that carry it. Don’t use polyurethane available from home improvement stores. They are for wood floors and furniture only. Here is an example of excellent polyurethane.
I coated my garage floor with a metallic epoxy, 2 coats primer & 2 coats epoxy. Then I sanded the floor to prepare for an application of a solvent based polyurethane top coat. After a thorough cleaning (sweeping, vacuuming, wet mopping), the final step was to wipe the floor with denatured alcohol. After the top coat dried, there were small bumps over every inch of the garage floor. I am sure these are not air bubbles or dust particles. Precautions were taken. Another website says that denatured alcohol should only be used to clean the floor for water based top coats. Mineral spirits should be used solvent based top coats. Is this correct and, if yes, is it likely the denatured alcohol was the cause of the bumps all over the floor. I don’t want to repeat my mistake. Thank you.
Hi Chuck. No, denatured alcohol should not have an effect with any concrete coating. It’s commonly used for just what you did. We cannot comment on it’s effect on polyurethane for wood floors, furniture, etc. It’s a completely different formula, many of which are oil-based and non of which are compatible with concrete coatings. There is always something that sets off the type of reaction you had though. High humidity can cause polyurethane to bubble like that. So can air moving across the surface or from the coating being applied too thick. If air is moving across the surface, the coating will cure faster at the surface and not allow the solvents to escape fast enough and bubbles will form. If it’s applied too thick, the coating will begin to set up before all the solvents can evaporate out. That is why it’s thin to win for polyurethane – just the opposite of epoxy.
Hi – nice column, we coated our garage floor years ago using Rustoleum with the color chips. We now have some rust in a corner, paint spills, and some bare places where the coating stuck to hot tires. Do I need to strip the whole floor, or can I clean and touch up the rough spots? Thanks for any advice.
Hi Ted. Rust-Oleum does not have touchup kits, so you would be required to purchase a full kit. You can certainly touchup those spots, however, it will be very obvious and they will stand out. Coatings do not blend like paint on a wall does when you touchup. The overlap marks stand out and the color tone will be off.
If you want to use the recoat primer, we recommend first etching the bare spots with the supplied solution from the new epoxy kit and then clean the entire floor surface. You can then apply the primer and then the new coating.
Hello. So i epoxied my floor with the chips then used a glossy clear coat. Some areas are semi glossy and some are less glossy. This was done about 2 months ago. I would like to apply a high gloss finish. What preparations do i need to do. Thanks.
Hi Anderson. You would do as in instructed in the article above. Degloss and rough up the surface with 120 grit sandpaper. Sweep/vac, wipe with denatured alcohol and then apply a new coating.
Awesome thanks