Resinous Flooring Base Coats: VBP (Vapor Barrier Primer) Epoxy vs. Polyurea vs. Polyaspartic

A solid foundation is crucial for a long-lasting, high-performance resinous flooring system. The base coat plays a critical role, providing adhesion to the substrate, a solid foundation for subsequent layers, and often, critical moisture mitigation. While polyurea and polyaspartic have gained popularity, especially as topcoats, VBP epoxy often remains the king of base coats. Here’s why:

Vapor Barrier Primer (VBP) Epoxy: E4E-100 VBP available at Epoxy Depot

Pros:

• Unmatched Moisture Mitigation: This is the core strength of VBP epoxies. They are specifically formulated to block moisture vapor transmission from the concrete slab, preventing bubbling, delamination, and other moisture-related failures in the flooring system. No other resinous coating type matches the level of protection from hydrostatic pressure, 25 lbs. per 1000 sf, as is seen in the E4E-100 VBP, and moisture vapor that a properly formulated VBP epoxy provides.
• Superior Adhesion: Epoxies are renowned for their excellent adhesion to concrete. They penetrate deep into the concrete pores, creating a strong mechanical bond that resists peeling and delamination, even under heavy traffic.
• Excellent Foundation: Epoxies provide a very stable, level, and consistent surface for subsequent layers, allowing for optimal performance of the entire flooring system. The slow cure of epoxy also contributes to its superior penetration and adhesion.
• Self-Leveling and Smooth Canvas: VBP epoxies, such as the E4E-100 VBP, are normally installed at 100 ft2 per gallon. This thickness allows the product to self-level and fill in most defects left after a proper preparation step. This is paramount when installing a system, such as metallics or neat systems that require the smoothest base possible.
• Cost-Effective for Moisture Control: While the material cost might be slightly higher upfront, in some cases, the long-term cost-effectiveness of preventing moisture-related failures makes VBP epoxy a smart investment for both the contractor and homeowner. This is especially true on high dollar installations like a metallic or quartz flooring system.
• Proven Track Record: Epoxies have a long and successful history in resinous flooring, with a proven track record of durability and performance.

Cons:

• Slower Cure Time: Compared to polyurea and polyaspartic, epoxies have a slower cure time, which can extend project timelines. However, this slower cure also has its advantage of penetration. One exception to this rule is the E4E-100 VBP that is available at Epoxy Depot. The E4E-100 VBP is available in normal (16-20hr), Fast (12-16hr), and Ultra (2-4hr) set times. This has considerably narrowed the set time gaps between VBP Epoxy, Polyurea, and Polyaspartic.
• Less UV Resistant (on its own): Epoxy is not UV-stable on its own, but it is generally covered with subsequent layers. As long as the VBP epoxy is buried underneath subsequent colored layers, the possible yellowing won’t be noticeable.
• Less Temperature Resistance: Epoxy has a hard floor of 50 degrees when it comes to acceptable installation temperatures. This means that the floor and ambient temperatures must be greater than 50 degrees for proper cure. Epoxy can become brittle when exposed to constant freezing temperatures once the installation is complete, as well.

Polyurea:

Pros:

• Rapid Cure: Polyurea’s cure time is extremely fast, usually around 2 hrs., allowing for quick return to service, a significant advantage in time-sensitive projects.
• Flexibility: They offer good flexibility, making them suitable for areas with slight substrate movement or temperature fluctuations. These characteristics make polyurea well suited for both interior and exterior projects, as well as coolers and freezers.
• Abrasion Resistance: Polyurea’s provide good abrasion and impact resistance.
• More Temperature Resistance: Most polyurea’s can be installed at temperatures below 50 degrees, some claim they can be installed in below zero-degree temperatures.

Cons:

• Poor Moisture Tolerance:
  1. Polyurea’s are very sensitive to moisture during application, requiring a very dry substrate. Polyurea also offers very little resistance to hydrostatic moisture issues, to the point that polyurea’s should not be used in the presence of hydrostatic pressure. This limits their use as a reliable base coat.
  2. Polyurea’s offer little resistance to hydrostatic nor vapor pressure over the long term. Often polyurea’s highest resistance to hydrostatic pressure is 3 lbs. per 1000 sf. Moisture content on your Tramex CME5 Meter shouldn’t be over a 2-3% reading for most polyurea’s. Compared to VBP epoxy, polyurea has a considerably lower moisture tolerance. Again, this limits their use as a reliable base coat.
• Weak Adhesion to Damp Concrete: Even slight moisture in the concrete can severely compromise adhesion, leading to failures.
• Pin holing and Outgassing: The fast cure can sometimes lead to pin holing and outgassing issues if not prepped or applied meticulously.
• Self-Leveling and Smooth Canvas:
  • Unlike VBP epoxies, Polyurea goes down much thinner, approximately 180-200 sf per gallon. The lack of thickness doesn’t allow the product to self-level and fill in most defects left after a proper preparation step. This is paramount when installing a system, such as metallics or neat systems, that require the smoothest base or “canvas” as possible. This limits polyurea as a good basecoat in these situations.
  • If polyurea is used as a basecoat and the concrete is extremely porous, you will run the risk of losing the product to the substrate. This contrasts with VBP epoxies in that polyurea is a much thinner liquid when it is first mixed and applied, at a thinner rate. When this happens, it causes a 2-fold problem. First, since the material is applied at such a thin rate, you will not have the self-leveling and defect filling characteristics that you get with a VBP epoxy. Second, this can cause inexperienced contractors to continue their broadcast step, without realizing that there isn’t enough polyurea left on the surface to adhere to your broadcast material. At this point, the contractor runs the risk of losing the adhesive properties of the polyurea with the broadcast material because the polyurea is “lost” into the porous substrate.
• Difficult to Re-Coat: Re-coating may present difficulties as the rapid cure results in a very dense, smooth surface. The recoat windows are much shorter, around 4-6 hrs., than what you get with VBP epoxies, which are usually 24 hrs.

Polyaspartic:

Pros:

• Fast Cure: Like polyurea, polyaspartics cure rapidly, 2 to 4 hrs., minimizing downtime.
• UV Stability: They offer better UV stability than epoxy, making them a better choice for areas with some sunlight exposure. These qualities make polyaspartic the best topcoat available for UV resistance over flake flooring and exterior projects.
• Flexibility: They offer good flexibility, making them suitable for areas with slight substrate movement or temperature fluctuations. These characteristics make polyaspartics well suited for both interior and exterior projects.
• Good Chemical Resistance: Polyaspartics provide good resistance to a range of chemicals.
• More Temperature Resistance: Most polyaspartics can be installed at temperatures below 50 degrees, some claim they can be installed in below freezing temperatures.

Cons:

• Limited Moisture Mitigation: While some polyaspartics claim moisture tolerance, they generally do not offer the same level of moisture vapor barrier protection as a dedicated VBP epoxy. The E4E Super Poly and E4E-87 polyaspartics available at Epoxy Depot have similar moisture tolerance to standard epoxy, which is much higher than any polyurea on the market today.
• Higher Cost: Polyaspartics are typically more expensive than epoxies, although costs are coming down.
• Short Pot Life: Their short pot life can be challenging for inexperienced applicators.
• Difficult to Re-Coat: Like polyurea, re-coating may be difficult without proper surface preparation due to the rapid cure and smooth surface. The recoat windows are much shorter, around 4-6 hrs., than what you get with VBP epoxies, which are usually 24 hrs.
• Orange Peel When Used in Smooth Systems: Polyaspartics can leave a textured, orange peel, finish when used as a base coat for smooth floor such as metallics and neat systems. This finish doesn’t lend itself to creating smooth attractive floors. Therefore, it is recommended to use polyaspartics as a base for broadcast media and/or a topcoat for a textured floor system.
• Self-Leveling and Smooth Canvas: Much like polyurea, polyaspartics go down at a much thinner rate than MPB epoxies. They suffer from the same issues as polyurea regarding their self-leveling and smooth canvas characteristics. Depending on the system being installed, this may make polyaspartic a less attractive option as a base coat.

Why VBP Epoxy Often Reigns Supreme as a Base Coat:

While polyurea and polyaspartic have their place, often as topcoats or in very specific applications, VBP epoxy often emerges as the superior choice for a base coat, especially when moisture is a concern, and a solid foundation is needed.

• Moisture mitigation is paramount: In many environments, moisture vapor transmission from the concrete is a major concern. VBP epoxy is specifically designed to address this issue effectively, providing long-term protection and peace of mind. The others simply cannot compete in this aspect, especially when dealing with moisture levels that surpass 3 lbs./1000 sf /24 hrs.
• Adhesion is king: Epoxy’s superior adhesion to concrete creates a strong, durable bond that’s essential for the long-term success of any resinous flooring system.
• Foundation for Success: The stable and consistent surface provided by an epoxy base coat ensures the best possible performance from subsequent layers, be it a decorative flake system, a metallic epoxy, or a high-performance urethane topcoat.

Conclusion:

In the realm of resinous flooring base coats, while the rapid cure and specific properties of polyurea and polyaspartic have their merits, VBP epoxy stands out as the most reliable and effective choice, particularly when moisture control and long-term adhesion are critical. Its proven track record, exceptional moisture mitigation, and superior adhesion make it the preferred foundation for a wide range of resinous flooring applications, ensuring a durable, high-performance, and long-lasting floor. For most applications, building your system on the back of a strong VBP epoxy base coat is the best path to a successful resinous floor installation.