Skip to content

7 Reasons Why Epoxy Coatings Fail

7 reasons why epoxy coatings failOur team gets asked all the time about why floor coatings fail.   Sometimes it’s for a garage floor that was painted with a big-box store’s epoxy kit.   Other times it’s a commercial service garage where the epoxy just won’t stick.   The reasons can vary, but I’m going to attempt to describe the most common reasons why epoxy coatings fail (this will typically hold true for other types of coatings such as polyaspartic or polyurea). 

Improper Surface Preparation

Too often, an epoxy paint kit from a big box store will instruct the DIY user to just clean the floor or etch it with muriatic acid.   Cleaning along is NEVER enough.   Acid etching, while a valid preparation method, will only work if the concrete’s pores are open enough to allow the acid to react and remove the laitance (the thin cement paste on the very top).  Acid etching will also not suffice for areas of the concrete which are sealed, oil stained, painted or contaminated (with wax, tire shine or other chemicals).

To ensure a proper concrete surface profile (CSP 2 or 3), we normally utilize our shrouded concrete grinders. On rare occasion, we may also shot blast the concrete.  For more information:   Epoxy Floor Coatings: Concrete Surface Profiles Explained

Contaminated Concrete

Even if the concrete is properly prepared, contaminants such as fatty acids (from cooking), silicone, siloxane and acrylics can soak in deep enough to still present an issue for proper coatings adhesion.   Often, heavily contaminated concrete areas must be heavily shot blasted (CSP-4 or greater) or cut/replaced.  

Poor Bond Strength

Contaminated ConcreteThis is one of the areas where professional coatings shine and DIY epoxy paints fail.   A good coating will have an adhesive strength that exceeds the concretes pull-strength.    Most kits fail here, as they are often just an epoxy fortified latex paint or have too many fillers (which make the epoxy easier to roll out and cheaper, but greatly decrease its bond strength).

Insufficient Wicking / Wet-Out

A good coating should “wet-out” the properly prepared concrete – meaning it soaks into all the open pores and surface imperfections created by the prep process.   Materials that setup too quickly, are too thick to impregnate the pores or shrink too drastically during curing will not fully wet-out the concrete.

This issue is often encountered by the “professionals” using the newest, state of the art, 1 day coatings.   These new installers don’t understand that the materials have setup too quickly to actually soak into the concrete – leading to premature failure of the coatings.    This issue is very common with new companies who are trying to do 1 day floors in extremely hot, humid weather.  To learn more, check out:  Garage Floors Coatings: One Day Installations

Moisture Problems

While not typical in garages of Pennsylvania, Maryland and Virginia, there are some situations where a garage may have moisture issues under the concrete slab that effect the ability of coatings to perform properly.   When too much moisture is trying to migrate upward through a concrete slab, it will put pressure on the coatings and, once high enough, that pressure will force either the coatings off the concrete or the coatings will pull apart the near-wear-surface of the concrete.

These problems usually exist due to poor garage floor construction (no stone base under the concrete slab) or due to water migration issues (spouting and down spouts directing water under the garage floor). On occasion, they may exist due to improper grading of the landscaping around the garage.     While very uncommon, our staff does proactively check for these types of issues when evaluating the garage for potential customers.

Excessive Humidity

Excessive humidity during the coatings installation can affect the inter-coat adhesion (the strength of the bond between layers of polymer coatings).   In particular, polyurethane, polyurea and polyaspartic are more humidity sensitive than most epoxies and acrylics.   Too must humidity will cause delamination, cloudiness and improper curing.

When applying coatings, the installers must be aware of the environmental conditions and adjust based upon humidity/dew point, temperature and other weather factors.

Product Mixing Issues

If products are not mixed at the proper ratios and for the proper amount of time, the coatings will not cure properly. In addition, many coatings are sensitive to the amount of air that is entrained during the mix process.


Mike Mincemoyer is the President of Stronghold Floors and one member of the ownership team.   Mike has assisted many residential and commercial customers to determine why previously installed coatings failed and replaced them with proper coatings systems.     He has assisted many homeowners to determine whether coatings were feasible in troubled basements and on-grade slabs.