Polyurea coating with silicone top coat on commercial flat roof

Polyurea is an incredibly versatile coating material with numerous commercial, industrial, and residential applications. It is best known for its exceptional waterproofing capabilities, extreme durability and flexibility, and fast drying time.

In this guide, we take an in-depth look at this remarkable and multifaceted roof coating chemistry.

Attention! Interested in a fluid-applied roof coating system for your roof? Click here to find an American WeatherStar Approved Contractor in your area.

What Is Polyurea?

Polyurea is an elastomer consisting of isocyanate (A-component) and synthetic resin (B-component). This type of “reaction” product is created via a process known as step-growth polymerization.

The isocyanate and resin components can be formulated to improve specific physical properties, such as dry time, moisture resistance, flame retardants, pigmentation, and other qualities.

Polyurea was introduced in the late 1980s, so it is a relatively newer roof coating technology. Early material formulations were especially hard, offering little to no elongation or elasticity. Over time, its elongation was improved, thus opening the door to numerous other applications (more on this below).

Recommended reading: For an in-depth look at the various types of roof coating chemistries, click here.

Aliphatic vs. Aromatic Polyurea

Polyurea is available in two varieties: aliphatic and aromatic.

Aliphatic polyurea is best suited for top-coat applications as it offers superior UV resistance and color stability. It costs more than the aromatic variety (nearly twice as much) but requires less material to achieve the desired film thickness during application.

Aromatic polyurea is primarily used as a base coat due to its lack of UV stability. It will gradually break down, discolor, and chalk if exposed to the sun’s UV rays; therefore, it must be top coated to ensure performance.

The Pros of Polyurea Coating

Waterproofing

Polyurea forms a seamless, leak-free membrane capable of withstanding permanent ponding water conditions. The polyureas used in commercial roofing are also used in many water containment applications such as reservoirs, pipelines, and wastewater treatment tanks, among others.

Durability

Polyurea-based coating systems are incredibly durable and flexible. They possess exceptional elongation and tensile strength, making them ideal for commercial roofing and surface/floor coating applications. They also exhibit excellent chemical, corrosion, and abrasion resistance.

Fast-Drying

Polyurea is an extremely fast-setting material. Depending on its formulation, it can cure within seconds to minutes of application.

High-Build Application

One of the most significant benefits of polyurea is its ability to build high mils during application. Unlike other coating materials, which require multiple passes to reach the same dry film thickness, polyurea can be applied at a rate of up to 500 mils in one pass.

Versatility

Polyurea can be formulated to achieve a wide range of properties based on its application. It fully adheres to a variety of common roofing substrates, including concrete, metal, wood, and spray polyurethane foam, without the use of a primer. It also performs effectively in a wide range of temperatures and humidity levels.

The Cons of Polyurea Coating

Equipment Costs

Applying polyurea coating systems requires plural-component spray equipment, which is very expensive. Most rigs run anywhere from $20,000 to $50,000, with fully-equipped mobile units costing upwards of $100,000 or more.

Furthermore, the equipment is highly technical and requires many hours of hands-on training to operate proficiently.

Color Stability

Aromatic polyurea provides a matte finish that will darken and chalk if exposed to UV radiation. For outdoor applications that require an aesthetic appeal, the aliphatic variation is recommended for its superior color stability and glossy appearance.

Limited Adhesion to Itself

Once cured, polyurea does not adhere well to itself. This lack of adhesion can lead to complications during the installation process.

Surface Prep

Surface preparation (typically sandblasting or priming) is paramount to a successful polyurea coating project. While this is more of a precaution than a con, most polyurea system failures can be attributed to inadequate or improper surface preparation.

How Much Does Polyurea (Roof Coating) Cost?

The material cost for a polyurea roof coating system ranges from $1.25 to $1.75 per sq. ft. Overall costs (including installation) will vary based on the size/complexity of the roof, condition of the existing substrate, material thickness, choice of top coat, building location, warranty requirements, etc.

Polyurea is slightly more expensive than some alternative roof coating systems (see chart below).

System/material Low-end cost (per sq. ft.) High-end cost (per sq. ft.)
Polyurea $1.25 $1.75
Acrylic $.90 $1.75
Silicone $1.10 $2.00
Urethane (Polyurethane) $1.10 $2.00
Liquid Rubber (EPDM) $1.50 $2.50
Spray Polyurethane Foam (SPF) + Coating $2.50 $6.00

How Long Do Polyurea Coatings Last?

Most polyurea roofing systems are warranted to last anywhere from 10 to 15 years. However, they can easily last up to 25 years or more with proper installation and routine maintenance.

Moreover, a polyurea roofing system’s elastomeric top coat (typically silicone or acrylic) can be recoated numerous times throughout its lifespan to help increase longevity and ensure performance.

How is Polyurea Installed?

Polyurea is spray-applied on surfaces using highly-specialized, plural-component spray equipment.

The isocyanate and resin components that makeup polyurea are shipped to job sites in 55-gallon drums. The materials are transferred into separate tanks within a spray rig apparatus and heated to an appropriate temperature. The unit then pressurizes and pumps each component through heated hoses to a spray gun at a specific ratio (usually 1:1).

Polyurea spray rig from Graco

Images courtesy of Graco.

As the isocyanate and resin are dispersed, they react to produce the polyurea membrane, which is typically formulated to set within seconds to minutes of application.

Proper surface preparation is vital to the performance of a polyurea coating system. In most cases, abrasive sandblasting or primer applications may be necessary to remove any foreign contaminants and ensure adequate adhesion.

Applications & Markets for Polyurea

Polyurea coatings are used in many building and construction applications. They are also utilized throughout various other industries, including healthcare, automotive, marine, defense and security, irrigation, and material handling, among others.

The superior waterproofing qualities of polyurea make it an ideal solution for commercial and industrial roofing—with suitable substrates including metal, concrete, wood, and spray foam.

Additionally, polyurea serves as a reliable waterproof lining for storage tanks, pipelines, reservoirs, sewers, wastewater treatment, basement walls, and secondary containment applications.

The superior durability and abrasion resistance of polyurea make it an excellent protective coating for flooring, decks, parking garages, and truck beds.

Conclusion

Polyurea is an impressive coating technology with countless applications. Its resistance to ponding water, durability, and versatility set it apart from alternative coating solutions on the market. Furthermore, polyurea-based roof coating systems are a good investment, lasting anywhere from 15 to 25 years and having the potential to be recoated numerous times throughout their lifespans.

To learn more about the benefits of polyurea—as well as fluid-applied roof restoration from American WeatherStar—click here to speak with a customer service representative.