When polyurea coatings fail, it’s usually due to mistakes in surface preparation, mixing, or application conditions. Issues like delamination, blistering, cracking, and yellowing are common signs of poor installation. These problems often result from:

• Improper surface preparation: Contaminants like dust or oil, smooth substrates, or insufficient profiling prevent proper bonding.
• Moisture issues: High moisture levels or applying too close to the dew point can lead to blistering and poor adhesion.
• Mixing errors: Incorrect ratios or uneven mixing cause curing problems, brittleness, or sticky surfaces.
• Application mistakes: Uneven coatings, excessive thickness, or rushing edges can lead to runs, cracks, or peeling.
• UV exposure: Non-UV-resistant formulas degrade quickly under sunlight, causing yellowing and brittleness.

Proper preparation, moisture testing, and using the right materials are key to avoiding these failures. Polyurea coatings can last over 15 years if applied correctly.

Problems with a Polyurea Concrete Coating (or Polyaspartic)

1. Delamination and Blistering

Delamination happens when the coating separates from the concrete, peeling off in large sheets rather than breaking into smaller chips. With polyurea’s impressive tensile strength, it often comes off in one continuous sheet, making it clear that something went wrong during the installation process. One major culprit? Contamination on the surface.

Surface contamination is the leading cause. Dust, oil, grease, or soluble salts act as barriers, preventing the coating from bonding directly to the concrete. Instead, the polyurea adheres to these contaminants, creating a weak bond that eventually fails. Another factor is a smooth or glossy substrate, which doesn’t provide the roughened texture needed for the coating to grip properly.

Blistering, on the other hand, shows up as raised bubbles or bumps across the surface. This typically occurs when moisture gets trapped beneath the coating. As Marvel Industrial Coatings explains:

"A coating system is only as good as its bond to the substrate".

When water vapor builds up under the polyurea’s impermeable layer, it creates enough pressure to lift the coating off the concrete.

To figure out what caused the blisters, examine their undersides. A smooth underside suggests moisture contamination. A rough underside points to moisture during the application process or an overly isocyanate-rich mix. If the underside feels sticky, it likely means there was an issue with curing, such as an incorrect resin-to-hardener ratio.

Applying polyurea too close to the dew point (within 3°F) is a recipe for failure. Installers combat this by taking multiple moisture readings for every 100 square feet. If moisture levels are high, they’ll use a hydro epoxy primer to deeply penetrate the substrate and block vapor transmission effectively.

2. Cracking and Crazing

Cracking appears as visible lines running through the coating, while crazing forms a web-like network of fine surface cracks. Both are clear signs that something went wrong during the installation process. These issues are often tied to mistakes in mixing ratios, application thickness, or managing temperature. Let’s break down some common causes behind cracking and crazing.

Mixing ratios must be precise to avoid coating failure. When working with polyurea, it’s crucial to get the balance between the base component and hardener just right. If the mixture contains too much isocyanate, the coating can become brittle or fail to cure properly. On the other hand, improper mixing can result in a gummy, undercured coating. A simple 24-hour thumb test can confirm this – if the surface remains sticky, the mixture wasn’t right.

Overly thick coatings create internal stress. Applying the coating too thickly can lead to cavities, resembling melted candle wax, which causes uneven curing and stress points. To avoid this, installers should use a mechanical mixer with a whisk that’s at least one-third the diameter of the container. This ensures a more even mix and better results.

Temperature fluctuations during application can lead to problems. Concrete naturally expands and contracts with changing seasons, which puts stress on the coating. Applying the coating during rising temperatures can trap expanding air and moisture, creating pinholes and weak spots. A simple workaround? Apply the coating later in the afternoon when temperatures are more stable to reduce these risks.

UV exposure is a major concern for non-UV-resistant polyurea. Aromatic polyurea coatings degrade quickly under sunlight unless they’re protected with an aliphatic topcoat. Without this added layer, outdoor coatings can become brittle and crack over time. While pure polyurea can last up to 15 years – far outlasting professional epoxy’s 3–5 years – this durability hinges on proper installation and adequate UV protection.

3. Uneven Application and Coating Runs

Uneven finishes, like visible drips or patchy surfaces, often point to mistakes during installation. When you see areas that sag, run down vertical surfaces, or have thicker patches, it typically means too much material was applied in one spot or the application wasn’t done quickly enough to match polyurea’s fast curing process.

Polyurea cures at an incredible speed and doesn’t self-level, so precision and speed are non-negotiable during application. Any delay or misstep can lead to noticeable flaws.

"Once polyurea hits the floor, you’ve got a very short window to spread it evenly before it begins to set. Miss that window, and you’re looking at uneven surfaces." – Floor Shield Coatings

Applying too much material, especially near edges, can leave permanent defects. These might look like melted candle wax or, in worse cases, lead to "mud cracking." This happens when thicker areas develop deep, irregular cracks as the coating shrinks during curing due to excessive internal stress. Such issues highlight the importance of precision at every stage of the process.

Improper mixing is another culprit, potentially causing uneven curing, trapped air bubbles, and inconsistent thickness across the surface.

For professional results, installation must be handled with care. Experienced installers focus on edges and details first before moving to the main surface. To avoid these common pitfalls, it’s essential to trust skilled professionals like Croc Coatings. Their expertise and adherence to industry standards ensure a smooth, even application every time.

4. Edge Peeling and Lifting

Edge peeling is a common issue that highlights the challenges of achieving proper adhesion, especially at concrete boundaries.

When polyurea starts to lift at edges or corners, it signals adhesion failure. Unlike other coatings that may chip away in small fragments, polyurea’s high tensile strength causes it to pull away in large sheets when adhesion is compromised.

The primary culprit? Poor surface preparation. Polyurea cures quickly, so the surface must be properly profiled to ensure deep anchoring. Without an adequate texture, the edges fail to bond effectively. As Roy Magnuson, Owner of Allsource Supply Inc., explains:

"The best polyaspartic floor coating in the world won’t perform well if it’s applied over a poorly prepared slab".

Moisture is another major factor. Rising water vapor from the concrete slab creates hydrostatic pressure, pushing against the coating from underneath. This is especially problematic around control joints and edges. Polyurea applied directly to bare concrete can typically withstand only 3–4 lbs of moisture vapor emission per 1,000 sq. ft. over 24 hours. Anything beyond this can lead to edge delamination.

The risk increases significantly with "one-day" installation systems that skip moisture-mitigating epoxy primers, applying polyurea directly to bare concrete instead. Such shortcuts leave the coating vulnerable to peeling. To prevent this, professional installations require mechanical grinding or shot blasting to achieve a Concrete Surface Profile (CSP) of 2–3, ensuring the coating has a proper surface to grip.

Another factor is applying the coating too thinly at the edges. Rushing through edge details creates weak points that are prone to lifting under normal use. Companies like Croc Coatings prioritize industry best practices by addressing edges and details first, using moisture-mitigating primers and ensuring proper surface preparation for a durable finish.

sbb-itb-a0e5ae3

5. Yellowing and Brittleness

Yellowing and brittleness are more than just cosmetic issues – they signal deeper problems stemming from installation mistakes. If a polyurea coating starts to yellow or becomes brittle, it’s often due to errors in material selection or application. These flaws not only affect how the coating looks but also weaken its overall durability and performance.

UV radiation is the main cause of yellowing. When aromatic polyurea is exposed to UV light, its molecular bonds break down, leading to oxidative reactions that discolor the coating and create tiny cracks. Dang Minh Thuy from the Institute of Tropical Durability highlights this process:

"The color change of polyurea samples under the effects of UV radiation is very significant. The color change is clearly visible to the naked eye after 200 hours of testing".

Research from 2022 backs this up, showing that after just 200 hours of UV exposure, noticeable yellowing occurs, and after 1,000 hours, the coating’s gloss drops by a staggering 97.3%.

As UV exposure continues, brittleness sets in. Those micro-cracks caused by UV radiation can expand, eventually running through the entire coating. This makes the surface prone to chipping and structural failure, even under normal wear and tear.

Another factor contributing to brittleness is improper mixing of the coating materials. If the resin-to-isocyanate ratio is off, the coating won’t cure completely. This results in a thinner, undercured layer that remains weak and prone to damage. Southwest Exteriors cautions:

"If the coating mixture is not mixed at the proper ratio, this gumminess will never go away, and your coating will never cure fully".

To combat these issues, especially in areas with high UV exposure, it’s crucial to use an aliphatic polyurea or polyaspartic topcoat. Unlike aromatic polyurea, aliphatic formulations resist yellowing and maintain their structural integrity under UV light. Companies like Croc Coatings rely on UV-resistant materials and precise mixing techniques to ensure their coatings stay durable and visually appealing for the long haul.

6. Poor Surface Wetting

Poor surface wetting happens when polyurea coating fails to penetrate the pores of concrete and instead forms a thin, superficial layer on the surface.

Contaminants on the surface block absorption. Dust, oil, or grease left on the concrete prevents the polyurea from making proper contact. As RJ Evans Flat Roofing Limited highlights:

"If the substrate has been correctly prepared but not correctly cleaned the polyurea will start to pull away from any dust, oil or grease in contact with it".

Moisture disrupts bonding by halting absorption. Rebecca Harrell from Southwest Exteriors explains:

"When a polyurea coating comes in contact with concrete, it bonds into the concrete while seeking moisture".

Environmental factors also play a big role. For instance, if the substrate temperature is within 3°F of the dew point, even slight moisture can prevent proper adhesion. Additionally, air or moisture trapped in the concrete can cause outgassing during application, creating pinholes that weaken the bond. These challenges emphasize the importance of thorough surface preparation.

To avoid poor surface wetting, the same care required to prevent delamination and blistering must be applied. Techniques like sandblasting or shot blasting are effective for removing contaminants and creating a textured surface that enhances bonding. Moisture testing is also critical – concrete should typically cure for at least 28 days at 70°F (21°C) before applying the coating. If moisture levels are too high, using a hydro epoxy primer designed to mitigate moisture is a must. Proper primers and controlling environmental conditions are key to ensuring a strong, durable bond.

At Croc Coatings, we focus on meticulous surface preparation and thorough moisture testing to ensure our polyurea coatings adhere properly and deliver long-lasting performance.

Comparison Table

The table below outlines common polyurea coating failures, their root causes, and strategies to prevent them. Even small missteps in surface preparation or application can result in major issues.

Root Cause Category	Failure Type	Specific Cause	Prevention Strategy
Surface Preparation	Delamination	Smooth or glossy substrate	Use shot blasting or grinding to create an anchor profile for mechanical bonding. Poor surface preparation accounts for up to 75% of all coating failures.
Surface Preparation	Blistering	Salt or oil contamination	Clean thoroughly with solvent wipes or pressure washing; test for soluble salts.
Surface Preparation	Poor Surface Wetting	Dust, grease, or moisture blocking absorption	Remove all contaminants; ensure concrete cures for 28 days at 70°F (21°C) before coating.
Application Errors	Uneven Coating / Cavities	Applying too thickly around details	Coat edges and details first before covering the main surface.
Application Errors	Blistering / Gummy Film	Incorrect mix ratio or mixing too fast	Use plural-component equipment; mix at controlled speeds to avoid trapping air.
Application Errors	Edge Peeling	Missed recoat window	Follow manufacturer timing specs; use recoat primers if the window is missed.
Environmental Factors	Delamination	Substrate temperature within 3°F of dew point	Never apply when substrate is within 3°F of dew point.
Environmental Factors	Checking / Alligatoring	Application in excessively high temperatures	Apply during cooler hours when temperatures are within manufacturer’s range.
Environmental Factors	Pinholes	Outgassing from moisture in porous concrete	Apply during falling temperatures; seal porous substrates with epoxy primer.
Material Problems	Yellowing / Chalking	Non-UV resistant formula exposed to sunlight	Specify aliphatic polyurea or UV-stable topcoats for outdoor applications.
Material Problems	Cracking / Brittleness	Inflexible formula on moving substrates	Select 100% pure polyurea with high elongation (200% or more) for flexibility.

Conclusion

When polyurea coatings are applied incorrectly, the results are hard to miss. Issues like delamination, cracking, blistering, edge peeling, yellowing, and uneven surfaces often arise. These problems usually trace back to poor surface preparation, incorrect mixing, or unfavorable conditions during application. As RJ Evans Roofing explains:

"Due to polyurea having an extremely fast curing time it is extremely unforgiving if any mistakes are made".

A professional installation process avoids these pitfalls by focusing on precise steps, such as thorough moisture testing, mechanical profiling to reach a Concrete Surface Profile (CSP) of 3-4, and applying the coating under controlled conditions. These measures ensure a coating that can last over 15 years without failing.

For example, Croc Coatings applies 100% pure polyurea basecoats using the Penntek Evolution system. Their method includes industrial grinding, accurate moisture testing with tools like the Tramex CMEX5, and one-day installations, all supported by a 15-year manufacturer’s warranty.

When done right, polyurea forms a chemical bond with the surface, offering flexibility that’s 10 times greater than epoxy. It also stands up to freeze-thaw cycles, road salt, and chemical exposure, making it a reliable, long-term solution. Investing in skilled application not only prevents expensive repairs but ensures decades of durable performance.

FAQs

What are the main reasons polyurea coatings fail?

Polyurea coatings are prized for their strength and adaptability, but they aren’t immune to problems if applied incorrectly or exposed to challenging conditions. One of the biggest culprits behind coating failures is poor surface preparation. If moisture, dust, oil, or leftover coatings aren’t thoroughly removed, or if the surface isn’t properly cleaned and mechanically prepared, the coating won’t adhere as it should. This can lead to serious issues like delamination.

Another common problem stems from incorrect mixing or application. Polyurea coatings rely on a precise mix of two components in a specific ratio. Mistakes – whether it’s inadequate blending or applying the coating in less-than-ideal conditions like extreme heat, cold, or high humidity – can create weak spots, cracks, or even bubbles.

Finally, environmental stresses can take a toll over time. Factors like drastic temperature shifts, UV exposure, or moisture infiltration can weaken the coating. Choosing the right product for the specific environment and following proper installation practices are key to achieving a durable and long-lasting finish.

How does moisture impact the durability of a polyurea coating?

Excess moisture in the substrate can lead to vapor pressure, which weakens the bond between the surface and the polyurea coating. This often causes problems like blistering, delamination, and cracking, all of which can shorten the coating’s lifespan and effectiveness.

Proper surface preparation and addressing moisture issues beforehand are crucial for a durable, flawless finish. These precautions not only help avoid expensive repairs but also ensure the coating performs as intended for years to come.

Why is UV resistance crucial for polyurea coatings?

Exposure to UV rays can significantly impact the durability and look of polyurea coatings. Over time, sunlight can cause these coatings to fade, yellow, or lose their original color. Beyond the cosmetic effects, UV rays can also compromise the coating’s structural integrity, reducing its flexibility and overall strength.

Using a UV-resistant coating helps maintain the surface’s vibrant appearance and protects it from long-term damage. This makes it a crucial choice for outdoor areas like patios, pool decks, and garage floors, where constant sun exposure is unavoidable.

Related Blog Posts

• Polyurea Curing: What to Expect
• 7 Common Concrete Coating Defects
• How to Spot Defects in Concrete Coatings
• How to Prevent Polyurea Coating Failures