Introduction to Metal Roofs
A metal roof is one of the toughest and longest-lasting choices for both residences and businesses. They offer solid protection against rain, snow, and high winds. Metal roofs are gaining traction because they require little maintenance, have high energy efficiency, and provide a modern, sleek appearance. Metal roofs can last for decades, and with very little upkeep that involves regularly maintaining your metal roof, you can extend the additional resistance to UV rays, corrosion, and extreme temperatures.
While metal roofing has built-in durability, using another protective layer can even further extend a roof’s life. That’s the true value of a metal roof coating.
What Are The Advantages of Metal Roof Coatings?
Many people think of a roof “coating” meaning paint. However, a metal roof coating is a specific protective membrane that provides:
- Protection of the roof material from corrosion, UV degradation, and leaks
- Sealing of seams or small openings to prevent water intrusion
- Reflection of sunlight – blowing through the roof for further energy efficiency and cooling cost savings
- Extension of the roof’s life by an additional 10–20 years, provided it is properly applied and maintained
From a property owner’s perspective, this approach extends the time between repairs, allows for roof replacement to be postponed, and ultimately leads to cost savings.
Types of Metal Roof Coatings
Acrylic Coatings
- Water-based, cheap, and easy to apply for a DIYer
- Good UV protection and reflective properties, which keep the heat absorbed in the building down
- Best used in hot/dry climates
- Equipped: Will degrade when ponding water is present or when extreme temperature fluctuations occur.
Silicone Coatings
- 100% waterproof – silicon can be used on flat or low slope roofs, which have ponding or standing water
- Outstanding UV stability with extended reflective performance
- Suitable for wet and humid conditions
- Cons: It may be slippery when wet, and dirt collects more easily; it is more expensive
Polyurethane Coatings
- Durable and wear-resistant, making them perfect for roofs where hail, debris, or heavy foot traffic is expected.
- They also form strong adhesion and have chemical resistance.
- They outperform acrylic coatings when there is standing water.
- Cons: More difficult to apply, less reflective, and more expensive
Elastomeric & Specialty Coatings
- Elastomeric coatings: Flexible and will contract and expand with the outdoor temperature
- Fluoropolymer (Kynar®) coatings: Great pigment retention and frequently factory-applied on high-end commercial builds
- Bitumen blends: Excellent waterproofing for flat roofs, but typically less energy efficient than modern coatings.
Some Things to Think About When Selecting a Roof Coating
- Climate: Wet climates typically require silicone; hot and sunny climates prefer acrylic coatings
- Purpose of the roof: Heavy foot traffic or industrial work will be best suited for polyurethane coatings
- Substrate: Galvanized steel, Galvalume, and aluminum all behave differently with coatings.
- Value vs performance: Acrylic is “cheap” for the initial investment, but silicone and polyurethane will maintain a longer life as a premium coating
Simple recommendations: use polyurethane for roofs that will be exposed to hail or foot traffic; use silicone for roofs that will experience rain, humidity, or standing water; use acrylic for reflective, inexpensive protection; and utilize elastomeric coatings for roofs that will be in climates experiencing a range of summer and winter temperatures.
Metal Roof Underlayments and Coatings
The material of your roof can dictate the effectiveness of a protective coating. A few material types are:
- Galvanized Steel: Coatings with rust-inhibiting properties are important
- Galvalume: This material is naturally corrosion-resistant, though coatings may extend the life
- Aluminum: Aluminum does not rust, but will benefit from UV and waterproofing protection.
The thickness of the coating and the compatibility of the product are also very important. The thinner and more incompatible the coating, the sooner it has to be replaced.
When to Consider a Coating for Your Metal Roof
- Paint splitting, rust, or corrosion
- Energy bills are rising because of heat absorption.
- Minor leaks (drips) or seams separating
- If you see chalky residue coming from your roof panels, you should consider a recoat.
Metal Roof Coating Maintenance & Repair
- Coatings are not “set-and-forget” systems, and typically need to be checked at least two times per year (Spring and Fall)
- Once or twice a year, perform a low-pressure wash (no pressure washer) to remove dirt and debris, such as leaves and algae.
- Inspect the roof and perform any repairs needed for the roof (scratches/peeling/seams)
- Depending on what product was used, the climate, etc., you will notice you will need to recoat your roof in 10-15 years anyway at the most.
Best Practices for Applying a Roof Coating
- Inspect and repair fasteners, seams, and minimum panel closures.
- Pressure wash the entire roof with a commercial-grade cleaner.
- Remove any rust via brushing or blasting, and prime any bare areas.
- Apply the coatings as evenly as possible over the surface of the roof, applying at least two coats and applying the second coat in a different direction than the first.
- Follow the manufacturer’s instructions on them for both coverage and drying time.
Common Situation Issues While Applying a Roof Coating
- Ponding water will break down acrylic coatings and promote mold and mildew on a roof.
- UV degradation will incur chalking, fading color, and a lack of protection.
- Poor preparation will incur blistering, peeling, or complete loss of adhesion.
- Using the wrong product could cause cracking from thermal expansion.
Cost Factors: Professional vs DIY
- Professional: $1.50–$4.00 per sq. ft. (labor and materials) and often comes with warranty options.
- DIY: $0.15–$2.75 per sq. ft. (materials only, no labor), no guarantee, and higher risk of failure
It may seem cheaper now, but the average person goes through some level of failures, because they did not do proper preparation or did not have a warranty, and end up paying more than they would have if they had just paid a professional to coat it the first time with the warranty.
F.A.Q.
What is the difference between coating and painting?
A metal roof coating is a liquid-applied, protective membrane that provides waterproofing, sealing, UV resistance, and stops corrosion from forming on your roof. Coatings are also more durable and offer longer/safer performance DIY or paint solutions.
How long does a metal roof coating last?
Acrylic will last 5-10 years, though silicone and polyurethane are typically 10-15 years or greater, depending on prep and adding. Any can last longer, done properly with the right maintenance.
Can you coat an old or rusted roof?
You can coat an older/rusted roof, as long as the roof is properly cleaned and prepped prior to adding the coat. Removing rust, repairing seams, priming bare areas, and cleaning the roof are a must.
Will a roof coating drop your energy bill?
It can. A reflective coating will aid in stopping or preventing solar heat from being absorbed, reducing temperature internally, thus reducing air conditioning costs. Usually, the amount of reduction varies based on sealants, etc.
How often should I recoat?
Most people tend to recoat their roofs approximately every 10 years. However, the type of product used and climate factors can shorten this timeframe or provide additional insulation benefits.
Will coating guarantee the sealing of a leak?
Coating does seal minor leaks and seams, but structural problems always need to be repaired prior to applying any coating. Correcting weak structural spots ensures leaks become even bigger problems faster, after re-applying the coating.
Mark Franklin, owner of Roof Rescue in Idaho Falls, Idaho, has been a trusted name in roofing since 2014. Serving Idaho, Montana, Wyoming, and Utah, Roof Rescue specializes in commercial and residential roof replacement and installation. Recognized for community initiatives like the “Operation Roof Rescue” program, which provides free roofs to local heroes, Mark combines professionalism with a passion for giving back. With 16 years of industry experience, an A+ Better Business Bureau rating, and glowing customer reviews, Mark’s leadership embodies quality and community-focused service.
