Debunked: Aluminum vs. Steel in Commercial Roofing Systems

Architectural sheet metal products must be carefully chosen according to budget and design constraints. Many metals on the surface seem level-like appealing options: copper, stainless steel, steel, and aluminum. Architects and building owners must consider: What do I want the finished product to look like, and what is the useful life of the metal products? For example, copper can be used to complement the look of a historical building while still maintaining quality, as it is not corrosive. However, it is very expensive. Similarly, stainless steel – even less corrosive than other metals such as aluminum – often seems appealing but is also not cost-effective and cannot be painted, which is typically not a desired building roof aesthetic. When designing their metal roof systems, architects find themselves choosing between the two most common metals for commercial roof design: steel and aluminum.

Companies must look for cost efficiency and durability when designing architectural sheet metal products for a flat roof, metal roof system, or metal wall panel system. Aluminum and steel are constantly at war: which one is right for my building? Here, we debunk three common myths about aluminum versus steel roofing systems that will help you choose the right sheet metal products and metal paint warranties for your roofing needs.

MYTH #1: All I need is the right paint finish to protect my commercial roof.

The capacity of metal to withstand rust and corrosion is critical to its long-term effectiveness. Rust and corrosion degrade the waterproofing capabilities of a metal roof, as well as detract from its cosmetic attractiveness and shorten its service life. Metal panel finishes promise long-term durability, namely, the capacity to resist peeling, cracking, and discoloration. However, all prefinished product metals have a core of either aluminum or steel. No matter how effective the metal panel finish is in its resistance to corrosion after it is bought, metal panels and flashings are typically cut.

When these cuts are made, and raw edges are exposed, which can even happen upon buying the panels, the core metal is also exposed. Also, as the metal system is built, the prefinished panels are constantly penetrated with fasteners and rivets, further exposing the core metal of either aluminum or steel. It is almost impossible to account for all of the exposed areas of core metal in the building process, so the consumer must choose the most durable metal core possible. Even if steel receives a pre-coating prior to the paint finish, such as galvanized or galvalume, the core is likely to fail over a 10-20 year period. Aluminum metal typically has a lifespan of 20-40 years.

Contractors in the Jacksonville coastal region must consider the area’s high salinity. Our climate in the Southeastern United States is harsh, so roofs must be designed with the elements in mind. In fact, the area from Daytona Beach, FL, to Savannah, GA, has the highest salinity content in the United States. You should learn about the products that have been tried and proven to perform in our region; sometimes, codes and ordinances will automatically narrow your selection. In Register Roofing’s home state, for example, all exterior building materials must have a “Florida Product Approval,” or they cannot be used. Register Roofing suggests a less corrosive material than steel: aluminum within the Northeast Florida and Southeast Georgia commercial roofing market. 

MYTH #2: A finish warranty ensures a long-lasting roof.

Before choosing a metal roof or wall system with a warranty, do your homework, ask questions, and read the warranty carefully. Keep a close eye on the small print. In the event that a consumer files a claim, you will want to double-check and verify what the manufacturer will cover. Often, commonly covered paint warranty items include a 20-30 year paint finish warranty on a roofing coat finish that appears attractive because it covers cracking, flaking, peeling, chalking, and color fade. However, since most of these warranties come from paint companies, often, these warranties only apply to the steel or aluminum roof coating and not to the core material, which is the most imperative part of the roofing system. 

The base metal on which the actual paint is put is referred to as a substrate. Without a warranty on the substrate, the metal can rust from the core and bleed out. Before you buy, be sure your substrate is covered by a warranty because if your paint fails due to corrosion of a substrate that isn’t covered by a guarantee, your alternatives are restricted, and you may have little to no compensation for it. Always be aware of any warranty restrictions and limits so that you can work with a reliable vendor that stands by its warranties. Because purchasing a metal roof or wall system is a significant investment, make sure you do your homework by asking the following questions: 1. What does this warranty cover? 2. What does this warranty not cover? 3. Specifically, does this warranty cover substrate corrosion? 4. Are there any particular restrictions or limits to the warranty that apply or don’t apply?

Knowing what to look for when settling on a metal roof or wall system can help you make the most informed decision, leading to the best warranty. Builders and architects in Northeast Florida and the Southeast Georgia area specify aluminum for building envelopes because they know that aluminum is less corrosive than steel and can withstand the high salinity in this local environment. In theory, all cut edges of the steel roof product could be treated with a sealer, which would work; however, this painstaking process is not practical or cost-effective to install. 

MYTH #3: Steel costs less than aluminum.

While this myth is true as an initial investment – steel is a less expensive roofing material than aluminum – steel almost always costs more in the long run. Often, steel is chosen because it is cheaper than aluminum. It seems appealing to go for a metal of a lower cost. After all, aluminum metal, on average, costs about 25% more than steel. There are some advantages of steel over aluminum, which is the strength of the metal. Steel products will provide superior wind uplift resistance on projects with high wind pressures. In addition, steel offers superior performance in projects or regions where hail ratings are required. 

However, it’s critical to think about the environment of your commercial roofing system: What kind of weather will it encounter? One must consider whether aluminum or steel roofs will last longer in an environment of such high salinity levels. Of course, any building owner wants their roof to last as long as possible. Under the test circumstances used in the Corrosion Comparison of Galvanized Steel and Aluminum in Aqueous Environments for the International Journal of Automotive and Mechanical Engineering, aluminum was shown to be more corrosion resistant to both rainwater and saltwater than steel. Because aluminum is far less corrosive than steel, it is also far less likely for an aluminum roof to rust and incur costs over time. 

Corrosion interrupts routine operations and necessitates significant repair and replacement of failing assets, in addition to endangering public safety. Aluminum is one of the most valuable materials in construction because of its low density, high elastic elasticity, thermal and electrical conductivity, corrosion resistance, and ability to create alloys with a variety of elements. Therefore, almost all installed products by Register Roofing are aluminum to ensure the highest quality roof in Northeast Florida and Southeast Georgia markets. Standard thicknesses of aluminum metal roofing and flashings provided by Register Roofing are .032”, .040”, and .050”.

Considering these three myths about aluminum versus steel roofing systems will help you choose the right sheet metal products to ensure you are designing and building the perfect roof. 

Is it time to re-roof your building? Are you building a commercial building, a multi-family residential property, a government facility, or a manufacturing complex? For over 40 years, Register Roofing has been providing commercial roofing solutions throughout the Southeast. Contact Register Roofing and let us demonstrate how we can provide an expert solution.


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