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Preparing A Garage Floor For A Coating With Onfloor

Ongoing wear and tear can make garage floors old, worn, and stained. But you can enliven your concrete garage floors with a fresh coat of epoxy sealant.

But this isn’t as simple as splashing some paint down on the floor or rolling on some sealer. You want to make sure that your garage floor is properly prepped to appropriately interact with the coating. If you don’t take the time to prepare the floor, your project will likely fail and you can ruin your beautiful, natural concrete.

Poor floor prep is the biggest reason that garage floor coating projects fail. You can have the greatest epoxy product in the world, but it will look damaged and cheap if the floor isn’t prepped properly.

So we’re going to take you through the specifics of the preparation process, so you can have a quick and easy epoxy application.

1. Get the manpower.

Preparing and sealing your garage floor can be done by one person but it’s much more efficient with at least two people. One of the biggest mistakes we see for DIY garage projects is a lack of appropriate manpower and surface preparation prior to applying the coating.

Grinding can be time-consuming for larger floors. If you can’t keep up with these processes, errors are inevitable. There are also fast curing sealers that make it difficult for one person to mix and apply.

We recommend having two or more sets of hands on deck. This helps cover a larger area in a shorter period of time, which minimizes the project length and reduces potential errors.  


Preparing A Garage Floor For A Coating With Onfloor


2. Read through the instructions.

If you’ve chosen the epoxy or paint that you want for your garage floor, you’ll want to read the manufacturer instructions. This will tell you exactly how the floor needs to be prepped.

You want to make sure that you follow these instructions as closely as possible.

3. Check for sealer.

If your garage floor has been previously sealed, this will need to be removed before adding a new coating. Sealer fills in the pores on the surface of the concrete, making it impossible for additional coats to adhere.

Epoxy won’t adhere to sealed or painted concrete at all. Applying paint to sealed floors will create a marbled, uneven appearance that dries in unattractive patterns.

Not sure if your garage floor has been sealed? Do the water test. Simply sprinkle water on the surface of the garage floor. If the water beads up immediately, then there’s a sealer on the concrete. If the water slowly sinks in and turns the concrete a darker color, there is likely no sealer or paint.

4. Do the moisture test.

You can’t apply epoxy or paint to moist concrete. Look on your floors for damp areas, which are usually darker or have beaded water.

You also want to check for efflorescence. This is a white powder that forms when moisture rises up through the concrete and reacts with excess lime and salts. The water then evaporates from the surface, leaving behind a white powder. Efflorescence can also form from humidity and condensation.

If there are visible signs of moisture, you’ll want to conduct a calcium chloride test. Check out how to conduct the calcium chloride test and what it means for your floors.

Even if there aren’t visible signs of moisture, there could be water quickly evaporating through the concrete. Contact Onfloor to learn how to thoroughly check for moisture in your concrete.

Note: Newly poured concrete needs to cure for a minimum of 30 days. Curing helps release moisture so it’s dry and ready for prepping. If you try to add a coating too early, it can trap the moisture inside and ruin the natural material.


Preparing A Garage Floor For A Coating With Onfloor


5. Repair cracks.

Look for any cracks, pits, or spalling in the concrete that needs to be repaired. You’ll want to fill in these cracks to create an even, unmarked floor before adding another coating.

Learn how to repair cracked concrete floors here.

Do not use a latex crack repair product. These are too soft for concrete and epoxy, and they shrink as they age. They are easily broken in garage settings.

Epoxy is self-leveling, but it won’t fill in cracks by itself. If you don’t first fill in the cracks, the epoxy will actually look pitted and darker in the damaged areas of the concrete.

Some companies will tell you to repair cracks after you grind the floor. This can work, but you’ll usually have to re-grind after filling the cracks anyway. Grinding after the repair ensures a smooth, level surface that blends the entire surface seamlessly.

6. Remove stains.

You want to get rid of all oil and grease stains, which are especially common on garage floors. Be especially aware of tire dressing, which acts like a coating-repellent sealer. Check out these interesting concrete stain tips and tricks with the Reader’s Digest.  

You also want to remove all glues and mastics. This gets rid of all of the “gunk” on your floors, leaving only the concrete material itself. This allows for a more level and smooth epoxy coating application.

Check out our Onfloor mastic and glue removal products here.

We recommend the OF16S-H for garage floor preparation. It’s a high-speed machine, 120V power machine, which allows it to remove even the toughest glues and mastics. The machine is easy to use and the high tool speed allows it to achieve production rates as high as 300 square feet per hour.

7. Clean the surface.

Your floors are ready to be “profiled.” Profiling is the process of grinding down the top layers of the concrete garage floor, exposing the pores of the natural material. This allows the epoxy coat or stain to penetrate and adhere to the concrete pores, creating the strongest hold.

There are several options for cleaning your concrete floors: We typically recommend grinding, as it shows better and longer-lasting results and is a very reliable preparation method.

Cleaning Garage Floors OnFloor


Grinding is the preferred method of cleaning and prepping for most professional installers.  

This can be an extensive process, but it shows the greatest results for beautiful garage floors. Learn how to grind your floors here.

We recommend the OF16Pro, which has a variable speed. This means you can grind at the maximum effective tool speed to ensure the smoothest and cleanest floor. It also works well to grind, polish, sand, and resurface—making it the best tool for a number of at-home flooring projects!

Don’t forget to vacuum after you grind the floors. (when vacuuming silica dust, always use a HEPA filtered vacuum and a high-quality dust mask)The vacuum removes all remaining dust and contaminants from the grinding process. Thoroughly vacuum the floor to create a clean space for the coating. If you neglect this step, you could trap dust and dirt under the coating, which can affect the bond and create an unattractive and marked flooring.

Try out our easy to use Dynavac PRO 1600IC HEPA vacuum to quickly and effectively pick up all the dust and dirt in your garage—both after the grinding process and whenever your garage needs a cleaning!


Your floors are clean, grinded, and prepped—now you can apply the epoxy!

You can learn how to paint your garage floor with epoxy here.

Not sure where to start with your flooring project? Not sure you’re prepping the concrete the right way?

Contact Onfloor for a free consult about your floors!New call-to-action