What is an Elastomeric Roof Coating?
Elastomeric roof coatings are liquid-applied waterproof membranes formulated to adhere to a clean substrate or existing roof covering, to renew, repair, or improve waterproofing and emissivity performance. These coatings are easy to apply and provide a flexible protection layer that adheres to a variety of surfaces. The quality, durability and results depend highly on the coating's raw materials as well as how the surface is prepared and coating is applied.
Elastomeric roof coatings use polymer binders (e.g., acrylic, silicone, polyurethane) that form flexible, elastic films; this gives them the ability to stretch and recover. Unlike built-up roofing, which relies on multiple layers of bitumen and reinforcement to create a thick membrane, elastomeric coatings form a thin, seamless surface that can accommodate normal roof movement. They’re typically used to restore and protect existing roofs and may require reinforcement at seams and details. As with other coatings, elastomeric liquid-applied coatings' performance and longevity depends on the specific chemistry and proper surface preparation. The chemistry and adhesion properties determine which roof types are suitable for these kinds of coating applications.
The elastic properties of an elastomeric roof coatings allow it to expand and contract with the roof as temperatures change through the seasons. It is installed as a continuous, seamless, monolithic membrane (not floating) without joints, overlaps, or other similar vulnerabilities. All major surface cracks, holes or damage must be repaired prior to application, but when properly applied the elastomeric coating will seal and waterproof small cracks and fissures. No coating can waterproof an existing damaged roof with significant ponding or other water-related issues; proper drainage and slope are essential to a watertight roof system regardless of the type of roof covering used. Depending on the existing surface and its condidtion, you can use roof & flashing tapes, fiberglass, or other common techniques to repair most minor roof damage before applying an elastomeric roof coating.
Bright white reflective coatings like Deck Flex Elastomeric Roof Coating or Ames Premium Roof Armor Elastomeric Roof Coating, for example, can also protect a roof from ultraviolet (UV) light and can lessen the effects of urban heat-island emissions. This will help reduce energy costs by reflecting sunlight and reducing heat transfer into the building, leading to lower cooling costs in the summer months.
Some elastomeric roof coatings can extend your roof's life by 10-20 years while reducing energy costs and protecting against UV damage. Depending on the chemistry and adhesion properties, liquid-applied elastomeric roof coatings are suitable for various existing roof surface types, including metal, asphalt, built-up, spray foam, plywood deck roofs, some tiles, and more.
Types of Elastomeric Roof Coatings
Acrylic Coatings
Acrylic elastomeric roof coatings are highly reflective, making them excellent for areas where UV protection is a key requirement. They're durable and work well on roofs with proper slope and drainage. However, acrylic isn't the top choice for roofs with ponding issues.
Polyurethane Coatings
The professional choice is a polyurethane elastomeric roof coating for flat roof situations and areas subject to higher than average foot traffic. Ideal for commercial buildings and areas requiring access to plant and equipment. Resists ponding well but may yellow and lose reflectivity over time. Maintainability can be an issue as dirt and debris can stick to the surface and resurface preparation may be required before re-coating is possible. Not everything sticks to polyurethane, so ensure the product is compatible with the existing roof surface before application.
Silicone Coatings
Silicone elastomeric roof coatings are the most hard-wearing and longest-lasting products currently on the market. Their high solids content means they achieve thickness levels easily and perform well in areas where UV protection is a major requirement. Silicone coatings resist ponding water and can be applied in damp conditions. They are also highly resistant to mold and mildew growth, making them suitable for humid environments.
SEBS Coatings
Synthetic rubberized coatings such as SEBS (Styrene Ethylbutylene Styrene) are recommended for metal roofs. They often have high VOC content, so care should be taken during application and these may not be available or compliant in all regions. SEBS coatings resist acid and alkali spills and cure very quickly. They are also highly flexible, making them suitable for roofs that experience significant temperature fluctuations.
Application Methods by Roof Type
An elastomeric roof coating can be used over several different roof types. Its versatility makes it a great choice for metal, bitumen, or spray foam roofs. If your roof is nearing the end of its warranty, an elastomeric roof covering can extend its life for another 10-20 years.
How to Apply an Elastomeric Roof Coating
The application method for an elastomeric roof coating depends on the roof and elastomeric roof coating type used. Most coatings can be applied with a brush, roller (see how to apply an acrylic elastomeric roof coating with a roller), or spray equipment. The surface must be clean, dry, and free of contaminants before application. Always follow the manufacturer's instructions for the specific product being used and use proper safety equipment during application.
Here are the steps for a typical acrylic elastomeric roof coating application:
Step 1: Clean and Dry the Surface
First, pressure wash the entire roof to remove all dirt, debris, and loose paint. For any moss or algae, scrub the area with a TSP solution before pressure washing. The roof must be completely dry before you proceed; any trapped moisture will cause the coating to bubble and fail later.
Step 2: Repair and Seal Seams
This is the most critical step for preventing future leaks. Apply a self-adhering, waterproof butyl rubber tape over all seams, cracks, and around the base of vents or pipes. Using an engineered seam tape is a modern, more reliable method than older techniques like fiberglass mesh.
Step 3: Apply the First Coat
Use a paintbrush to apply coating around the edges of the roof and any obstructions (a process called "cutting in"). Then, using a 3/4" nap roller, apply a thick, even layer of the coating to the main roof surface. Be sure to follow the coverage rate recommended by the manufacturer, which is typically around 100-150 square feet per gallon.
Step 4: Let the First Coat Cure
Allow the first coat to cure for a minimum of 24 hours in warm, dry weather. If the weather is cool or humid, wait a full 48 hours. The surface must be fully cured, not just dry to the touch, before you apply the next coat.
Step 5: Apply the Second Coat
Apply the final coat using the same method as the first, but roll in a direction that is perpendicular to your first coat (e.g., if your first coat was north-to-south, the second should be east-to-west). This ensures you don't miss any spots. Allow the final coat to cure for 24-48 hours.
Metal Roof Application
Metal roofing, commonly used for steel-framed commercial buildings, is light, long-lasting, and resilient but prone to rust over time. Using an elastomeric roof coating can extend the life of metal roofs by 10-20 years.
Preparation is key: ensure the roof is free from rust, staining, paint flaking, or chalking. Treat bare metal surfaces with a proprietary metal primer. Clean the roof with soapy water and ensure it's thoroughly dry before application. For metal roofs with significant surface rust, consider using a rust converter before applying the primer and coating.
Spray application is often the most efficient method for metal roofs, but rollers and brushes can also be used for smaller areas or touch-ups.
Asphalt Roof Application
Asphalt-coated materials like bituminous shingles can be covered directly with elastomeric coating. Use a stiff broom to remove loose material and ensure all shingles are securely adhered. For wider cracks in valleys or around service penetrations, back the coating with a fiberglass layer.
Built-Up Roof Application
Built-up roofs (BUR) are multi-layer systems with staggered joints. When leaks occur, elastomeric systems can avoid complete roof replacement. After proper remediation of loose, broken, and damaged material, residual problems can be overcome with elastomeric coating. Use a fiberglass mesh embedded in the coating to reinforce areas with cracks or blisters. Apply the coating in multiple layers to achieve the desired thickness and durability; at least two coats are recommended for optimal performance. Installation can be done with rollers, brushes, or spray equipment, depending on the roof size and complexity. Annual inspections and maintenance will help ensure the coating lasts and stays reflective.
Spray Foam Roof Application
Polyurethane spray foam roofs benefit greatly from elastomeric coatings as UV protection. The coating protects spray foam from UV degradation while reflecting sun rays and helping mitigate heat build-up inside the building.
Plywood Deck Flat Roof
Only multi-layer code approved elastomeric roof coatings can work for plywood deck flat roof projects. Use a built-up sandwich layer structure starting with stapled metal lath, covered with TetraCrete, fiberglass mesh, Deck Flex base coat, and finishing with a top coat for a durable, flexible roof that withstands traffic and temperature extremes. Without a build-up multi-layer system, plywood deck roofs will not be up to code for fire resistance, wind uplift, impact resistance, and other requirements.
Tools and Preparation
Elastomeric coatings can be applied like paint products with some specific considerations with respect to surface preparation. Use a 4-inch brush for edges and openings, and a roller on a long pole for larger areas. The surface must be clean, dry, and free of contaminants before application.
See also how to apply an elastomeric roof coating video for a more detailed walkthrough.
Performance and Longevity
How Long Does an Elastomeric Roof Coating Last?
A properly applied elastomeric roofing system should last at least 10 years and can often be guaranteed for up to 20 years. The longevity depends on the quality of the coating, the preparation of the surface, and the environmental conditions. Regular inspections and maintenance can help extend the life of the coating and the roof itself.
Will an Elastomeric Roof Coating Stop Leaks?
Ponding water is among the most common causes of leaks in flat roofs. While elastomeric roof coatings can seal small cracks and fissures, they are not a substitute for proper roof drainage and slope. Ensure that your roof has adequate drainage to prevent water accumulation.
One main benefit of silicone-based liquid-applied elastomeric membranes is their ability to settle into every fissure, crack, or hole. Larger defects can be addressed with fiberglass patches, while smaller, almost invisible problems are sealed by the material adhering to the surface. Ponding water is a common cause of leaks, so ensure the roof has adequate drainage and slope.
On roofs with valleys and multiple penetrations, regular expansion and contraction can create gaps for water entry. When checking for leaks, focus on these vulnerable areas first. Failed flashings around vents can be repaired by wrapping with fiberglass mesh and adhering with elastomeric solution.