The Importance of Metal Roof Sealant

Written on March 6, 2023 by Austin Matz

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Metal roofs offer many appealing benefits for homeowners; they’re highly durable, energy-efficient, and won’t burn in the event of a fire. A well-cared-for metal roof can last for decades, or about 40 to 60 years, which is more than double the life expectancy of the average asphalt shingle or single-ply roof.

However, if your metal roof doesn’t have a proper sealant, water can seep in, leading to rust that eats away at the roof over time. Are you wondering which metal roof sealant is right for you? This guide from our metal roof experts in Orlando, FL, can help you decide.

Different Types of High-Performance Sealants for Metal Roofs

When it comes to choosing metal roofing sealants, homeowners have four main options: silicone, polyurethane, polymer, and butyl. All provide strong adhesion to metal, but each has unique pros and cons.

Silicone Sealant

Of all types of metal roof sealant, silicone is the most resistant to hot and cold temperature extremes. It can withstand temperatures over 185 degrees Fahrenheit, so it’s an excellent choice for Florida’s scorching summer weather. Silicone also provides a strong seal against water and offers impressive UV resistance to protect against the Florida sunshine and rain.

However, silicone doesn’t hold paint well and has limited color options, so homeowners may find it difficult to match this sealant with the color of their roofs. It’s also one of the most expensive sealant options and is prone to tearing easily. Additionally, some products may contain acids that can corrode metal roof panels.

Polyurethane Sealant

Polyurethane is a non-butyl sealant with several benefits: it’s easy on the wallet, resistant to tears, and offers impressive load-bearing capacity. Unfortunately, polyurethane has a shorter lifespan than other sealants because it consists of organic material. Homeowners can expect this sealant to last five to ten years before it needs replacing.

Polyurethane also takes a long time to dry, and in very cold weather, it becomes difficult to apply and mold. Extended cold temperatures eventually cause polyurethane to break down, although this isn’t as much of a problem with Florida’s mild winter climate.

Polymer Sealant

Hybrid polymer sealants, such as modified polymer (MP) and modified silane (MS), offer strong UV and temperature resistance. In areas that get hurricanes, such as Florida, polymer sealants hold up very well. Polymer’s resistance to extreme weather is on par with that of silicone and even better than the protection polyurethane offers.

Polymer is also a good choice for people sensitive to volatile organic compounds (VOCs). Compared to other sealants, VOC off-gassing from polymer is quite low. Polymer sealants accept water-based paints well, allowing homeowners to match the sealant to the color of their roofs.

Polymer sealants have few disadvantages, but they can be quite viscous, meaning homeowners might find them difficult to work with. Some types of polymer also need adequate airflow and moisture to cure properly.

Butyl Sealants

Butyl sealants are ideal for preventing water infiltration between two pieces of metal. Butyl is a common type of sealant used for:

  • Roof valleys
  • Ridges
  • Eaves
  • Panel end-laps and side-laps

Butyl sealants are available in liquid (pumpable) or rubberized tape form. Butyl sealants last for years and don’t dry out, so they provide unbeatable adhesion for vents, seams, and non-exposed joints. However, these products don’t hold up to UV rays and bad weather, so you should only use them in areas where they won’t receive exposure to the elements.

Further Considerations for Metal Roof Sealant

Before you buy metal roof sealant, check the packaging for important information about its type, class, cure time, and intended use. This information will help you choose the sealant that’s best for your roof.


Sealants come in two types: Type M (multi-component) and Type S (single-component). Type M sealants need multiple steps to cure, but they cure quickly and offer the most reliable performance. Type S sealants will cure without any additional steps; they require less labor and are easier to use, but they are also more expensive and take longer to cure.

Cure Time 

Cure time varies depending on the type of sealant. Sealants that take a long time to cure can attract dirt and debris, which may weaken the bond between roof components. If too much debris becomes stuck in the sealant, you’ll likely need to remove it and apply a fresh coat, which wastes your valuable time and money.

If you’re working on a roof in an area that’s windy or dirty, such as a construction job site, opt for polymer sealant because it cures very quickly compared to other types.


On sealant packaging, you’ll find letter ratings that provide information about the product’s intended use. Here is an explanation of what each letter means:

  • M: Can come into contact with mortar
  • A: Can use with aluminum
  • G: For use with glass
  • O: Can use with all materials except glass, mortar, or aluminum


A sealant’s class represents its ability to expand and contract under movement and ranges from 12 to 100.

To find a sealant’s class, check its packaging. The first number indicates expansion ability, and the second indicates contraction ability. If you see only one number on the package, the sealant expands and contracts at the same rate.

For example, if your sealant has a 100/50 class, it will contract up to 50% of its original width and expand up to 100% of the original width. Experts recommend class 35 or class 50 sealants for use with metal roofs. These classes are capable of withstanding a moderate amount of movement without a risk of failure.

Contact Our Expert Roofing Company in Orlando to Learn More

If you need help making sense of sealant options for your metal roof, give our PRS Roofing team a call at (800) 750-9198! We’re here to answer your questions about the pros and cons of metal roofing and different types of metal roof sealants so you can make the best choice for your needs.

About The Author: Austin Matz

Austin Matz, a 28-year-old Central Florida native and Army veteran, boasts extensive expertise in the insurance and roofing industries. As the Operations Manager of PRS Roofing Company in DeBary, Florida, Austin skillfully navigates the complexities of the business. His background equips him to provide top-tier services while maintaining a strong commitment to customer satisfaction. When not managing roofing projects, Austin can be found sharing his love for the outdoors with his son, exploring new destinations, and creating lasting memories on the water.