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Debunking Metal Roofing Myths: Rust & Leaks

The resiliency, longevity and design versatility of a metal roof is truly unmatched. And yet, home and building owners can still feel hesitant to upgrade to a metal roof. Some believe that a metal roof is noisier (it’s not, thanks to insulation), and some think they are more prone to damage from extreme weather events like lightning strikes or hail (not true either due to high conductivity and high impact resistance).  

There’s a third widespread myth concerning metal roofs that needs clearing up, and it’s that metal roofs are more prone to rust and leaks. Thankfully, this is not true – rust and leaks are no match for a metal roofing system. Let’s explore the reasons why. 

Resisting rust with steel and aluminum 

It’s natural to have concerns around rust when considering a metal roof. This is in large part due to the fact that steel, one of the most common materials used in metal roofs, contains iron which can rust when exposed to oxygen and water. Unaddressed, the rust can then spread across the whole structure. However, thanks to advances in metal finishes and paint systems, metal roof panels made from steel, as well as copper and aluminum, can withstand rust and corrosion. 

For steel panels, a metallic coating is applied that is made of either zinc or a zinc-aluminum combination. This results in what is more commonly known as galvanized steel or Galvalume® steel. Because zinc has inherently strong anticorrosion properties and bonds well with other metals, it is the ideal coating choice for steel. According to the United States Geological Survey, half of all zinc that is produced is used to galvanize steel or iron to prevent rusting. Specialized paint is then applied over the coating in whatever color the home or business owner decides on for a beautifully unique, finished design.  

In addition to steel, metal roofing panels can also be made out of aluminum, a lightweight and durable material that is naturally resistant to corrosion and oxidation. As the world’s most abundant metal, aluminum is also a recyclable and energy efficient material. Aluminum reflects heat and cools quickly, contributing to metal roofing’s role in green building. Metal roofs made of aluminum are ideal for coastal regions, as aluminum’s anti-corrosion properties ensure that they will not decay from salt water or salt spray. Many leading manufacturers, however, offer warranties that include saltwater damage.  

Ensuring all parts of the metal roof assembly can withstand rust and leakage 

A metal roof may be at a higher risk to rust if not all components of the assembly were considered when creating a rust-free system. It is crucial that all screws and accessories that support the metal roof are safe from corrosion and installed correctly. A simple solution to sideline the risk of rust is to use standing seams or concealed fasteners. Instead of exposing clips or screws, standing seams make for a beautiful and cohesive design. By concealing the clips and fasteners, there are no penetrating holes in the panels or visible fasteners that would attract rust and corrode over time. 

Further, during installation, watch out for fasteners that are overdriven, underdriven or driven in at the wrong angle. Unproperly fastened panels can let in unwanted rust. If penetrating holes or cut edges exposing the bare metal interior to moisture does occur, Drexel offers our Edge Sealant which is used to prolong the life of steel and aluminum products. For saltwater warranties in coastal environments, Edge Sealant is required for aluminum cut edges. 

Offering further protection with high-performance paint systems 

Another component of the roof assembly to consider is the paint system. Many metal roofs are finished with high-performance coatings like polyvinylidene fluoride (PVDF). Also known as Kynar 500®, this formula contains a mixture of fluoropolymer resin and ceramic pigments, producing an incredibly strong bond that offers further protection for the roof. 

Available in a range of colors, these protective coatings help inhibit rust, but they also help resist water from leaking into the building envelope. Preventing leaks and moisture from entering a structure is one of the chief tasks of the roof. A coating on a metal roof creates a watertight system enabling rain and snow to shed easily and quickly.  

Corrosion-free peace of mind 

As the protective shield of a structure, the roof can encounter many natural threats, but metal roofs provide a resilient and lasting solution for ultimate peace of mind. With proper material selection, protective coatings, correct installation and occasional inspections for any scratches or holes, a metal roof will be safe from corrosion, rust and water leakage for its decades-long lifespan.  

For further peace of mind, Drexel Metals offers six different warranties (as no warranty is one size fits all), including a 35-year Gold Standard Warranty to meet the needs of roofing professionals. Learn more about our warranties.