Elastomeric Silicone Roofing System on Mod Bit

To many in the roofing industry, elastomeric coating systems are viewed as nothing more than a “band-aid” solution to stop leaks. While this may be true in some cases, many roofing professionals need to be made aware of the long-term benefits elastomeric coatings provide.

In this guide to elastomeric coating, we aim to educate commercial roofing contractors on this highly effective, albeit underestimated, roofing technology.

What Is an Elastomeric Coating?

Elastomeric coatings are liquid-applied roofing materials that cure into seamless, flexible, and rubber-like membranes. These coatings can be stretched to at least twice their original size (100% elongation) while returning to their original form without damage or distortion.

Elastomeric coatings (systems) are used to restore a variety of commercial roofing materials, including:

  • Built-up roof (BUR)
  • Modified bitumen (mod bit)
  • TPO
  • PVC
  • EPDM
  • Spray polyurethane foam (SPF)
  • Concrete

Elastomeric coatings form a thick (approximately 10x thicker than paint) yet flexible membrane that is easy to apply and highly adaptable to various atmospheric conditions. These coatings add an extra layer of waterproofing and UV protection to existing roof surfaces, prolonging service life and restoring performance.

Most elastomeric coatings can also be tinted to various colors and exhibit excellent long-term color retention. This attribute can help maintain the appearance of roof surfaces and mask signs of superficial damage, aging, rust and corrosion, and general wear and tear.

The Benefits of Elastomeric Coating

  • Waterproofing: Elastomeric coating systems can bond hairline cracks on roof surfaces, providing a watertight seal. Most solvent-based coating systems are even warranted to withstand ponding water conditions (more on this below).
  • Resists thermal movement: Once cured, elastomeric coatings bond aggressively to roofing substrates, providing a durable, flexible membrane capable of accommodating the natural expansion and contraction (thermal movement) of roof structures.
  • Seamless (monolithic): Most roofing systems have a lot of seams and penetrations, which are highly susceptible to water intrusion over time. Elastomeric coatings are applied in bonded layers to provide a completely seamless and self-flashing membrane.
  • Reduces energy costs: Elastomeric coatings offer exceptional thermal reflectivity and UV performance. Think of them as "sunscreen" for your roof. They effectively reduce heat flow on roof surfaces, resulting in average energy savings of up to 40%.
  • Prolongs service life: A well-maintained roof can be coated (and recoated), adding 10-20 years of serviceable life—depending on the type and thickness of the coating application.
  • Prevents rust & corrosion: Elastomeric membranes protect metal roof surfaces against the damaging effects of rust and corrosion.
  • Environmentally sustainable: Compared to replacement, elastomeric roofing systems are more environmentally sustainable. Roof tear-offs contribute massive amounts of waste to landfills yearly, while coating systems produce little to no waste.
  • Long-lasting & renewable: Most coating systems are warranted (labor and material to last anywhere from 5 to 25 years—some even go as high as 50 years. Once the warranty expires, more coating can be applied, and a new warranty issued. This process can repeat itself so long as the roof is coatable.
  • Cost-effective: Elastomeric roofing systems cost about half as much as a full-on replacement and are far less disruptive to business. The cost associated with elastomeric systems depends on roof size, roof construction, membrane condition, coating type, warranty requirements, installation method, etc.

Types of Elastomeric Coating

There are two types of elastomeric coating: solvent-based and water-based.

Solvent-based coatings are made up of liquefying agents that evaporate through a chemical reaction with oxygen. These elastomers have superior ponding water resistance and are less vulnerable to certain environmental conditions (i.e., humidity, temperature, etc.). In a water-based coating, humidity can prevent water from evaporating, making it impractical for use in some climates.

The two most popular types of solvent-based coating are:


Silicone elastomeric, the most popular type of coating in the industry, is the preferred material for flat roofs due to its superior ponding water resistance and UV stability.

The Advantages of Silicone

  • Ponding water resistance: As a moisture-cure substance, silicone will not absorb any additional water once cured—meaning it is fully resistant to ponding water.
  • UV protection: Silicone elastomeric coatings reflect up to 80-90% of the sun's UV rays.
  • Flexibility: Silicone elastomeric coatings effectively expand and contract with roof structures.
  • High solids content: This means less liquid material is needed during application to achieve the required dry film thickness (DFT).

The Disadvantages of Silicone

  • Easily attracts dirt: Silicone-coated surfaces accumulate dirt and dust, causing them to lose their reflective qualities over time.
  • Challenging to spray: Silicone elastomeric products can be challenging to spray. Problems are all the more likely if spray equipment is not properly cleaned and maintained.
  • Slippery when wet: Silicone-coated roofs are very slick if moisture is present. Installers typically implement a walk-path coating to identify designated walking routes if foot traffic is expected.


Urethane (polyurethane) is among the industry’s most durable and robust types of coating, although it is considerably more expensive than other kinds of elastomer.

There are two types of urethane elastomeric coating: aliphatic and aromatic. Each is suited for specific coating applications.

Aliphatic urethanes are used as a top coat for their superior UV stability and durability. They possess a low-to-moderate solids content and hold their color quite well.

Aromatic urethanes have a moderate-to-high solids content. They are used primarily as a base coat because they do not hold up well in the sun. Aromatic urethane is more cost-effective than the aliphatic variety.

The Advantages of Urethane

  • Durability: Urethane-based elastomers have exceptionally high elongation and tensile strength, enabling them to stretch and move with roofing structures.
  • Superior adhesion: Perhaps the most notable quality of a urethane elastomeric membrane is its ability to adhere—quite aggressively—to various commercial roofing substrates.
  • UV stability: Aliphatic urethane coating, which are white in color, produces a highly reflective finish that holds up well to UV exposure.

The Disadvantages of Urethane

  • Produces strong odor: Urethane emits quite a smell as a xylene-based material. Though this vapor is not harmful, it can be unpleasant—especially for a building's occupants.
  • Challenging to spray: Like all solvent-based coatings, elastomeric urethanes can be difficult to spray and harsh on equipment.
  • Shorter shelf life: Single-component urethane coatings are constantly curing, even in the pail. Their shelf life only ranges from 3–6 months.

Water-based coatings use water as their liquifying agent instead of chemical solvents. These elastomers have a minimal environmental impact and are touted for their sustainable manufacturing practices.

There is only one type of water-based coating suited for the demands of commercial roof restoration:


Acrylics, known as “the original” elastomeric coating, are ideal for roofs with adequate drainage—particularly sloped metal roofs.

In terms of volume, acrylics are essentially half solid material and half water, meaning much of the product is lost through evaporation during the curing process. As a result, acrylics—despite being cheaper than silicone and urethane—require more product during application.

The Advantages of Acrylic

  • Economical: Low cost and performance make acrylic elastomers a popular and sensible roof restoration solution.
  • UV protection: Minimizing the sun’s impact on roof surfaces helps sustain lower energy costs and cools roof surface temperatures.
  • Easy to work with: Compared to solvent-based coatings, acrylic (water-based) elastomers are much easier to work with and install.

The Disadvantages of Acrylic

  • Ponding water: Acrylic coatings should only be installed on sloped roofs with sufficient drainage. Ponding water on an acrylic-coated rooftop can be very problematic.
  • Limited application window: Water-based acrylics are prone to freezing at colder temperatures. Temperatures must be at least 50°F (and rising) for the coating to adhere properly to the roofing substrate.
  • Loss of mil thickness over time: Acrylic roofing systems tend to chalk over time, causing them to lose mil thickness as they age.

Recommended reading: For a more in-depth look at the various types of roof coating, check out this post: Which Roof Coating Performs Best?

Elastomeric Coating Cost Breakdown

Material Low-end cost (per sq. ft.) High-end cost (per sq. ft.)
Silicone $1.00 $2.00
Urethane (Aliphatic) $1.25 $3.00
Urethane (Aromatic) $1.10 $2.00
Acrylic $.90 $1.50

How Are Elastomeric Coatings Installed?

Airless Sprayer

Airless hydraulic sprayers are generally considered the most efficient method for applying elastomeric coating systems. These machines deliver a consistent and uniform coating application. On the downside, this equipment is expensive and requires some degree of technical knowledge to operate and maintain.

Tank Spreader

Tank spreaders efficiently apply any pourable materials achieving even, consistent coverages with a “gravity-fed” application. A tank spreader can be used on flat or ribbed surfaces without the risk of overspray. Clean-up is very simple with disposable or easy-to-replace parts.


A nap roller is the most straightforward method for applying elastomeric coatings. Although, this approach is usually reserved for smaller roofing applications or roofs with limited access.

Regardless of how they are applied, proper surface preparation (i.e., cleaning, priming, etc.) is key to the success of an elastomeric coating system. There’s a saying in the industry: “You’re only as good as what you stick to,” and surface prep is the only way to ensure proper adhesion.

Beyond surface preparation is the details. All seams, transitions, fasteners, etc., are coated with a thick waterproofing mastic. This step is vital for the system to expand and contract as the temperature on the roof surface fluctuates.

For more on the various application tools and equipment of elastomeric coatings, click here.


We have gone over what elastomeric coatings are, the available types of elastomeric coatings, and ways to apply them; the last thing to note is film thickness. It is essential to verify adequate film thickness to ensure the coating performs as intended. The film thickness of an elastomeric coating is what protects the roof from UV degradation. If a roof has insufficient film thickness, the coating will be unable to block UV rays and bridge cracks.

Elastomeric coatings are a great option to extend the life of a commercial roof. While these coatings are not a “one size fits all,” there is undoubtedly an option for your facility. Elastomeric coating’s waterproofing ability, UV protection, Flexibility, and durability are undeniable.

If you think your business could benefit from an elastomeric coating installation, contact us today to help you find American WeatherStar Approved contractors in your area.