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Why You Should Use an Epoxy Primer for Your Floor

epoxy floor primer

Epoxy floor primer

When to use an epoxy floor primer is a subject that is often overlooked by the average home owner who is investing in a premium garage floor coating.  In fact, many people aren’t even aware that they exist or think that it’s just an added cost that they don’t need.

Epoxy primers provide an abundance of benefits for your coating with some specializing in problems associated with the surface of the concrete itself.  With exception to the inexpensive one-coat epoxy paint kits, if you want to insure that you achieve the best possible adhesion and endurance of your garage flooring for years to come, then you should seriously consider the use of an epoxy primer for your floor.

Benefits of an epoxy floor primer

The benefits of using an epoxy floor primer for your garage are many.  Let’s take a quick look at these to get a better understanding of what they do.

  • They provide for better adhesion to concrete and the subsequent coats of epoxy.  This will result in a longer lasting and more durable garage floor coating.
  • They help to eliminate bubbles and pinholes that can form due to outgassing of the concrete.
  • Some epoxy primers are effective in providing a moisture barrier for garage floors that have light moisture problems such as efflorescence.
  • Most are moisture tolerant and work well when being applied in high humidity areas of the country.
  • They allow for the subsequent  and thicker base and top coats to achieve a higher dry film thickness since they are not soaking into the concrete.
  • Some are specialized such as oil blocking primers.  These are a solvent based primers made to cover concrete that has been contaminated by oil and can’t be completely cleaned.

How epoxy primers work

Epoxy adheres to concrete by forming a mechanical bond within the pores of the surface.  This is why you need to profile the surface by either etching or grinding the concrete.  Primers are designed to penetrate deeper into the pores in order to achieve a better mechanical bond to reduce the chances of delamination of a properly prepared surface.  As a result, it also produces a thinner epoxy film or tie coat that the next coat can chemically fuse with.  This process produces an even stronger bond yet and is why most contractors always use a primer.



Air bubbles and pinholes are created in epoxy from outgassing of the concrete.  Air in the slab will rise due to a temperature increase or change in humidity.  If it does this during the initial application and curing process of the epoxy, it can form bubbles or pinholes when the air escapes.  This is why it is always best to apply the first coat of any epoxy in the later afternoon hours when the air temperatures are decreasing.  It can also happen due to poor mixing of the epoxy or improper back rolling.

Because of their thinner film, primers reduce the likelihood of bubbles and pinholes forming as they soak farther down into the concrete to fill those voids that can hold air and reduce the chances of air finding its way to the surface.  If air does find it’s way to the surface, the bubble will usually pop and then slowly fill back in before curing due to the low viscosity of the epoxy primer.

Since most epoxy primers are water based, the chemical makeup provides for moisture tolerance and as a result some brands can actually be applied to a damp slab.  This is beneficial for the DIY epoxy installation that profiles the slab with acid etching.  Instead of waiting 24 -48 hours or more for the slab to dry completely, you can apply your primer when it’s still damp or if the humidity is up.

Many of these same primers will also form a vapor barrier to ward off the problems associated with moisture that tries to work its way to the surface.  If you think you have a moisture problem, contact the manufacturer first to determine how much moisture you can have in order to use their product.

Finally there is primer for those who thought they couldn’t coat their garage because of oil contamination that could not be removed completely.  Some manufacturers make an oil stop primer that is solvent based and works by actively seeking out and bonding to the oil contaminants embedded in the concrete.  These are usually dark in color however and need to be covered with more than one coat or with a full refusal paint chip application.

Will your epoxy floor coating fail without a primer?  No, if you prepped your floor correctly your coating will not fail.  However, with all the benefits that can be gained from using an epoxy floor primer, it’s hard to come up with an excuse not to.  They are definitely something to strongly consider and most cost less than the standard epoxy formulas due to their thinner film thickness.  If you want the most durable and trouble free coating that you can have for your garage, then the investment for a primer is going to be worth it for years to come.

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Comments

  1. Would you still suggest a primer on a garage floor with a polyaspartic epoxy and a really good profile?

    • Hello Grant. If you have a very good profile that was achieved by grinding, then most polyaspartics do not require a primer. However, always check with the manufacturer. Some applications may require thinning of the first coat and this acts as a primer.

  2. Are there any epoxies that don’t need primer?

    • Hello Miguel. Epoxies do not “require” a primer to work. However, a primer is a wise choice to use for all the reasons mentioned above and is also why professional installers use primer. They can’t afford to put down a coating that they might need to come back and repair at a later date, so they insure the quality of their coating by using it. You can install most epoxies without a primer and have good results if you have prepped the floor properly, but you will not benefit from the additional gains that a primer will provide.

  3. For a basement, should I use water based or 100% solid epoxy? Should I use a primer? If so what kind? I’ve decided on Armorpoxy, Armorgarage, or Budget Bob’s as my 3 possible companies I will order from. I would like this floor to be my permanent floor. Any suggestions? I’ve just heard that Rustoleum Epoxyshield (even the Professional kit) is not very good durability.

    • Hello Jeromy and thanks for visiting our site. Your question depends on how durable you want your floor to be. If you are looking for a high build coating that will give you the best protection for the dollar, then 100% solids epoxy is the way to go. Many manufacturer’s will use a water based primer however since it is not being used as the build coat. Both ArmorPoxy (which goes by ArmorClad for their residential products) and Armor Garage sell and recommend using a primer. Budget Bob’s does as well. ArmorPoxy and Armor Garage provide very good products. Budget Bob’s product changed after his death a few years ago. They do not provide technical data sheets online to compare, so we don’t have an opinion about their product.

      For long term wear, the EpoxyShield kits are not your best bet. The Professional series is better, but it is solvent based and you don’t want to be applying that in an enclosed area of the home. Also if you haven’t done so already, make sure to do a moisture test first since it will be applied in a basement.

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