In commercial construction, small decisions can have a long-lasting impact. A choice that may seem minor during design or procurement—like selecting a finish for your steel decking—can play a major role in how a building performs over time. One of the most critical finish options, especially for buildings exposed to the elements, is galvanized steel decking.
Despite how often it’s specified, there’s a lot of confusion surrounding what galvanized steel is, when to use it, and how it compares to other deck finishes like paint or bare steel. For contractors, specifiers, and engineers working on high-performance buildings, understanding these details is essential. Choosing the wrong finish could lead to faster degradation, costly maintenance, or premature failure. But choosing the right one gives your building a stronger foundation from day one.
What Is Galvanized Steel Decking?
Galvanized steel decking is standard cold-formed steel deck that’s been coated in a protective layer of zinc. This zinc coating is what gives the product its corrosion resistance and makes it suitable for projects where exposure to moisture or the environment is a concern.
There are two common ways to apply this protective layer: hot-dip galvanization and electroplating. Hot-dip galvanization is the most common method in the steel decking industry. It involves immersing the steel into a bath of molten zinc, which creates a strong metallurgical bond and a uniform, durable coating.
This zinc layer serves a dual purpose. First, it acts as a physical barrier between the steel and the environment. But even more importantly, zinc also offers sacrificial protection. That means if the coating is scratched or cut—say, during installation—the surrounding zinc corrodes first, shielding the steel underneath from rust. This self-healing property is one of the reasons galvanized steel has earned such a strong reputation for durability.
Where Galvanized Steel Decking Works Best
Galvanized steel decking makes the most sense in environments where the steel is exposed to moisture, humidity, or fluctuating temperatures. That includes parking garages, stadiums, open-air mezzanines, industrial processing facilities, and coastal buildings. In each of these applications, bare or painted steel would struggle to maintain its integrity over time. Rain, salt, condensation, and chemical runoff are all threats to untreated steel. Galvanization provides a reliable defense.
Understanding G60 vs. G90 Coatings
When specifying galvanized steel decking, understanding the difference between G60 and G90 coatings is critical. These designations refer to the total amount of zinc coating applied to both sides of the steel during the galvanization process. The number represents the coating weight in ounces per square foot, so G60 has 0.60 oz/ft² and G90 has 0.90 oz/ft². While that may seem like a minor difference, it has significant implications for corrosion resistance and long-term performance.
G60 galvanized steel decking provides a moderate level of corrosion protection and is sometimes used in interior environments or where exposure to moisture is limited. Because the zinc coating is thinner, it offers a shorter lifespan in harsh environments and may be more susceptible to corrosion if field cuts or scratches go untreated. G60 is often chosen in applications where cost is a higher priority than durability, such as temporary structures, dry interior spaces, or where the decking is protected by a robust building envelope. However, even in those cases, specifiers should carefully assess humidity levels, condensation risk, and exposure to chemicals or salt before defaulting to a thinner coating.
G90 galvanized steel decking, on the other hand, is considered the industry standard for structural applications where durability is non-negotiable. The thicker zinc coating provides better corrosion protection, especially in open-air, coastal, industrial, or high-humidity environments. This makes G90 the preferred option for long-term applications like parking structures, outdoor mezzanines, and buildings with intermittent moisture exposure. While G90 has a slightly higher initial cost than G60, its superior performance over decades often makes it the more economical choice when total lifecycle cost is considered. It’s also the more common specification in building codes and among SDI member manufacturers.
How Galvanized Steel Decking Compares to Other Finishes
It’s important to consider how galvanized steel compares to other common finishes. Painted decking is often chosen for interior environments or when aesthetics are a concern. It can be a cost-effective solution when the steel won’t be exposed to significant moisture. However, painted finishes are more vulnerable to damage during transportation and installation. A scratch or nick in the paint exposes the raw steel, opening the door for corrosion to start. That’s not the case with galvanized decking. The zinc layer is baked into the steel through the hot-dip process, making it far more durable in handling and field conditions.
Bare steel decking, on the other hand, offers no corrosion protection at all. It’s the lowest-cost option up front, but those initial savings may come at a much higher price later in the building’s life cycle. In dry, conditioned interiors, it might perform well enough. But even then, condensation, leaks, or humidity can still cause long-term damage. That’s why galvanized steel is often recommended even for enclosed structures, especially in areas where climate or exposure is unpredictable.
Why Galvanized Steel Decking Delivers Long-Term Value
When you choose galvanized steel decking, you’re not just buying a corrosion-resistant product. You’re buying confidence in the long-term performance of your building. That confidence is backed by real-world longevity. In typical environments, G90 galvanized steel can last 50 years or more without major degradation. Even in more aggressive environments, like coastal zones with salty air or industrial settings with chemical exposure, galvanized decks outperform most alternatives.
But choosing galvanized steel isn’t only about longevity. It also brings efficiency to the job site. Because the coating is applied at the manufacturing level, installers don’t need to field-prime, paint, or otherwise treat the deck. That means faster install times, fewer finishing steps, and fewer complications in the field. There’s also less concern about damaging the finish during handling. Galvanized steel can take more abuse without compromising performance.
Installation and Handling Best Practices
Installing galvanized steel decking is relatively straightforward, but paying attention to a few key practices will help maximize its long-term performance. Even though the zinc coating adds durability, it’s not indestructible, and careless handling or exposure can reduce its effectiveness. Below are several best practices to follow throughout the project lifecycle.
Trends in Welding for Steel Deck
One of the most common places where corrosion begins is along unprotected cut edges. During installation, it’s often necessary to trim panels to fit or create openings for pipes and conduits. These cuts expose the raw steel beneath the zinc coating.
To maintain corrosion protection in these areas, it may be necessary to treat cut edges with a zinc-rich primer or sealant. While the galvanized layer offers some sacrificial protection, applying a touch-up coating helps extend the lifespan of the steel and prevents rust from creeping in at the margins.
Avoid Galvanic Corrosion from Mixed Metals
Galvanized steel is vulnerable to galvanic corrosion when it comes into contact with incompatible metals in the presence of moisture. Common culprits include copper, brass, and uncoated carbon steel. When two dissimilar metals touch, the less noble metal (in this case, zinc) can corrode more rapidly, especially in damp conditions.
To avoid this, use compatible fasteners and hardware. Screws, washers, and anchors should match the deck’s galvanization or be specially coated for use with zinc. In locations where contact with other metals is unavoidable, use isolators or gaskets to physically separate the materials.
Use Proper Fasteners and Connection Methods
Fastening methods matter. Whether you’re welding, screwing, or using mechanical fasteners, the chosen connection system should be compatible with galvanized coatings. Some fastening processes, like welding, can burn off zinc in the heat-affected zone, which reduces corrosion protection.
If welding is necessary, take precautions to limit coating damage and apply post-weld treatments to restore corrosion resistance. Many contractors prefer mechanical fastening for this reason. It’s faster, cleaner, and better preserves the deck’s protective coating.
Store Material Correctly On-Site
While galvanized steel is rugged, improper storage can still undermine its integrity before it’s even installed. Deck bundles should be kept off the ground and stored in a dry, well-ventilated area. If the material must be stored outside, keep it covered with waterproof sheeting, but allow for ventilation to prevent condensation buildup.
Prolonged contact with standing water, mud, or vegetation can cause white rust or staining, even on zinc-coated surfaces. Storing the material at a slight slope helps shed water and minimizes pooling between panels.
Protect During Extended Construction Timelines
In fast-paced projects, decking is often installed and immediately covered with concrete or roofing systems. But on slower or phased jobs, galvanized deck may be exposed for weeks or months. During these periods, proactive protection is essential.
Avoid exposing installed decking to aggressive construction materials like harsh chemicals, wet mortar, or de-icing salts. If other trades will be working on top of the deck before it’s enclosed, consider using a temporary covering or walk-off mats to prevent abrasion and contamination.
Sustainability and LEED Contributions
Beyond performance and ease of use, galvanized decking can also contribute to sustainability goals. Steel itself is highly recyclable, and most galvanized steel products contain a high percentage of recycled content. When specified thoughtfully, galvanized decking can help contribute to LEED credits under categories like Building Product Disclosure and Optimization or Construction Waste Management. Its durability also means fewer replacements or repairs down the line, which reduces the environmental impact of material production and transportation over the life of the building.
Clearing Up Common Myths
While galvanized steel decking delivers on performance, there are a few common misunderstandings that persist in the field. One of the most frequent is the belief that galvanized decking doesn’t need any protection at all during installation. While the coating is tough, it’s not invincible. Excessive exposure to harsh chemicals, abrasion, or poor storage can still cause problems if not managed properly.
Another myth is that all galvanized coatings are the same. As we mentioned earlier, there’s a significant difference between G60 and G90 in terms of coating thickness and performance. Choosing the wrong one could result in under-protection in environments where moisture or chemical exposure is high. G60 may be acceptable for interior use or short-term projects, but G90 remains the go-to standard for structural applications.
It’s also worth noting that galvanized steel can be painted if needed. This is sometimes done for aesthetic reasons or to provide an additional layer of protection in extreme conditions. However, painting galvanized steel requires special surface preparation to ensure proper adhesion. The surface may need to be cleaned, roughened, or treated with a bonding primer to avoid peeling or flaking.
Galvanized Steel Decking as Part of a Holistic Building System
One of the most helpful things a design team can do is treat galvanized steel decking as part of the larger building system, not as an isolated component. This means coordinating with MEP trades, reviewing fire rating requirements, and considering how the deck interfaces with insulation, vapor barriers, and structural supports. Galvanized decking can play a major role in UL-rated fire assemblies, for example, or in managing sound transmission in multi-tenant buildings.
In some projects, galvanized decking may be specified alongside other performance criteria, like acoustics, thermal efficiency, or even seismic performance. That’s why many building teams rely on design resources from the Steel Deck Institute, which offers standards, testing data, and design tools to help engineers and specifiers make informed decisions.
The Bottom Line: Strength, Protection, and Peace of Mind
Galvanized steel decking offers an unmatched blend of strength, durability, and value. It’s not just about protecting the steel; it’s about protecting the investment made in every building that depends on that steel. From moisture resistance to sustainability benefits, galvanized decking checks all the boxes for high-performance construction. And as building codes evolve, environmental demands increase, and lifecycle expectations rise, this simple zinc coating continues to prove itself as one of the most cost-effective and trusted finishes in the industry.
For engineers, architects, and contractors looking to build smarter, stronger, and longer-lasting structures, galvanized steel decking isn’t just a good option—it’s often the best one. The more you understand about its benefits and applications, the more strategic you can be in using it to its fullest potential.
If you’re specifying steel deck for an upcoming project and want guidance on finishes, coatings, or compatible products, resources from the Steel Deck Institute and its member manufacturers can help you make the right call. Investing a little more in the right finish today could save years of headaches down the road.