Surface Preparation in Epoxy Flooring: Explaining the different methods

scarifying concrete floor before epoxy coating

All seasoned epoxy applicators will agree that thorough surface preparation is key for the long term success of a successful flooring project. There is nothing more heart breaking for a client to discover his beautiful epoxy floor to start chipping and breaking just a few weeks or months after completing. Most of the time poor surface preparation is the culprit. The substrate had not been properly ground, cleaned and prepared to be able to accept the epoxy.

grinding concrete floor
Diamond tool floor grinding – One of the most common methods

So what constitutes proper surface preparation? Which method is the best? This is a good question as depending on the application in question you may need to approach the problem in a different manner. I have identified several levels of surface preparation according to their mechanical intensity. Some methods (like sanding) are light and barely scratch the surface. Other methods (like scarifying can) be deep and intense.

Sanding – This is the lightest form of surface prep usually done with an angle grinder or a light floor sander. Done with sanding paper (of varying grits) attached to a disc. Such surface prep is only appropriate for re-coat jobs, or if you are just applying a light paint job. Even if you use a rough, low grit sandpaper, the surface scratch will be little

Stone Grinding – These machines were very popular before diamond grinders came out, but I see that epoxy applicators are not using them much these days. Basically this is a heavy floor grinder that has stone tools fastened to the bottom. Works well for a soft concrete surface but it does not grind well on hard concrete or epoxy.

Diamond Grinders – I love diamond grinders because they are so versatile. Most diamond grinders allow easy switching out of diamonds. They can therefore handle all types of floors from soft cement to hard concrete. They can strip old paint layers and clean out oily patches of the floor.  Diamond grinding leaves a much deeper and harsher scratch profile of the floor (compared to sanding) and this therefore enables better bonding of the primer to the floor. I also find if you are dealing with messy and contaminated patches, a bit of persistent diamond grinding is enough to give you a nice clean floor. This is my preferred choice if I’m working with standard floor systems up to 2-3mm. Watch this video to understand how a diamond grinder works

Shot-blasting is a more aggressive method of surface preparation than grinding. It leaves a nice deep profile that makes the bonding conditions for high build flooring systems (3mm and over) ideal. However shot blasting requires very good high quality concrete to work properly. If you try shot-blasting a weak substrate you could very well end up damaging the substrate.

Finally, Scarifying is my solution of last resort. This is a very aggressive form of surface preparation that digs into the surface. Several time when I was faced with horrible looking contaminated floors, using a scarifier saved the day. We were able to clean the surface and apply a new thick heavy build coat.

Scarifying a damaged floor

As a final comment, the thicker the system that you plan to apply the deeper the preparation needs to be. This holds also vice versa. If you scarify a surface, you need a thick coating to cover that surface. A thin epoxy coat will not be able to fully cover the heavily scarred profile.

What are your thoughts on surface preparation? Please leave your comments below! And if you got value from this article, then maybe you should consider our online course for epoxy flooring! You will get many more useful insights and information in this jam-packed course.

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Akis Apostolopoulos

General Manager at Ktisis
Akis has been involved in the manufacturing and application of industrial floor coatings for the past ten years. He runs learncoatings which is an online resource training professionals on the use of epoxy floors. He is also General Manager of Ktisis, a manufacturer of flooring and waterproofing coatings.

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