By Steve Swaney
Steel has traditionally been the predominant metal used in post-frame construction, but aluminum is becoming a popular material for rainware, trim, liner and interior ceiling products in residential and commercial post-frame applications. While steel has some structural and thermal properties that make it best for certain uses, aluminum has advantages in other uses, and as a result is being considered by many builders for a number of components.
Competitive Cost
Some people experience sticker shock when they see the cost of aluminum on a price-per-pound or per cwt., but once they learn the approximately 65% less weight differential, the cost per lineal foot becomes pretty compelling to use. The typical steel panel is .015 min. gauge, 40.875” wide, and weighs around 2.10 per lineal foot, whereas an aluminum panel the same size weighs about .72 pounds per lineal foot, or about a third the weight of steel.
Corrosion Resistance
Aluminum has excellent corrosion resistance, which is why it’s been used so much for animal containment applications, such as chicken cages and hog pens. That’s because of the way aluminum is produced. It’s a solid substrate, unlike a steel (galvanized or Galvalume), which has a cold rolled base with a galvanized metallic alloy coating. That means when you shear steel, you have an exposed cold rolled steel edge which, short term, will create a very fine red rust line before it oxidizes over to reseal itself. Aluminum is a solid alloy plus one that is very resilient to many aggressive caustic, acidic, and more corrosive environments and applications.
Even with aluminum’s excellent corrosion resistance, it’s extremely important that animal containment buildings are effectively ventilated and drain animal waste toward the interior portion of the building, preventing stagnant fumes and runoff from being trapped against the metal surfaces. If you enter one of these buildings and you begin coughing or your eyes are burning, the structure is not effectively circulating and exhausting the toxic fumes. Hog barns are especially prone to this, based on some of the low ceiling designs. Even stainless steel will break down over time, despite it being the “Cadillac” of corrosion-resistant metals and double the cost.
Versatility and Formability
Aluminum is easy to work with and is a favorite material for applications that need a lot of deformation and shaping. That’s one reason that its use in the automotive sector is growing as body styles of cars and trucks and mass transportation vehicles become more aerodynamic with slope and curves to reduce air drag. That’s also a reason that it’s always been extensively used in the aerospace industry. The nature of aerodynamics requires lightweight, strong materials in sleek and creative shapes, angles, and curves.
Aluminum’s weight savings is making a big impact in other areas as well. A lot of new heavy electric utility lines use aluminum because their lighter weight compared to steel means that they don’t need as many large towers to support them over miles and miles. Most solar panels have a high aluminum content to them as well.
Alloy, Gauge, and Temper
Aluminum coil has a wide range of gauges, from aluminum foil to armor plating for defense vehicles. Aluminum’s combination of strength and ductility make it very unique. Aluminum beverage cans start as a flat rolled coil, are then formed into their various shapes and sizes in high speed and high volume can lines, which again show how dramatic the metal can be reshaped!
Aluminum is categorized by the term “alloy.” The predominant aluminum alloy for building products is 3105. 3003 is an alternative with less recycled content. 3004 and 5052 can also be used for building products, but 3105 is the primary alloy to request for in building products.
Aluminum’s other key specification for end use effectiveness is known as its temper, like grade in steel. This has to do with the annealing of the aluminum to achieve certain properties within each alloy. Aluminum has four primary tempers: quarter-hard symbolized with a 2, half-hard as a 4, three-quarter hard as a 6, and full-hard as an 8. Full-hard aluminum is equivalent to grade 80 steel.
Aluminum designated H28 is used for liner, building panel, and agricultural applications. H25/H26 is typically used for rainware, gutter, and soffit in residential products. H24 is softer and is used for standing seam, trim, edge metal, and architectural roofing. So, in summary, 3105 H24 through H28 are the alloys and tempers generally used for aluminum building materials.
Coil Sizes
Because of the weight differential between steel and aluminum, there’s a big difference in the coil footage. A steel coil might weigh 10,000 pounds, but an aluminum coil with the same outside diameter (OD) might only weigh 4,000 to 5,000 pounds. Domestically, the aluminum industry produces aluminum up to 64 inches wide for most building products. Some imported coils can go substantially wider, but most residential building products are narrow. So make sure your supplier factors the right OD and weights for your coils if you are new to using aluminum, as they are substantially different from light gauge steel coils.
Roll Forming
Roll forming aluminum is usually simpler and more consistent than roll forming steel. For example, aluminum is flat from edge to edge, where steel is rolled to a crowned center with the edges being several percent thinner than the center. The surface of aluminum is very smooth and consistent, and easier on your roll-former’s dies.
One area that aluminum can be a little more delicate is in shearing or cutting it to length. With aluminum’s forming properties, the metal has a tendency to deflect more than steel, so it’s crucial that you keep your shears well sharpened when cutting aluminum to prevent the bending of the edge when shearing. In folding or using a brake press, aluminum is very easy to work with. It accepts profiles and shape changes much cleaner and more effectively than steel and is lighter to load, position, and store after fabrication.
Common Current Uses of Aluminum in Non-Post-Frame Residential Construction
• Rain Gutters • Roof Vents • Hips • Drip Edges
• Chimney Flashing • Roof Ridges • Roof Caps • Roof Valleys
• Rake Edges • Gables • Gable Vents • Eaves • Soffits • Fascia
• Skylights • Dormers • Downspouts
Advantages of Aluminum for Post-Frame Residential Structures
Compared to steel, aluminum is more cost effective on a cost-per-linear-foot. It’s also lighter weight, so it’s easier to work with and more durable. It will outlast steel because it won’t corrode, whereas wherever steel has cut edges, they’ll rust.
A new trend we’re seeing is that aluminum, which has long been used in traditional residential construction, is now being looked at more by post-frame builders who for a sizeable percentage have been doing replacement metal residential roofing and are now getting more into total home construction.
Gutters, downspouts, soffit, and fascia, for example, are some of the most commonly made products in aluminum in traditional home construction. The post-frame builders were trying to make these out of steel, which is more of a challenge and expensive on a cost per foot. Drip edge is another one that’s relatively easy to manufacture. Because aluminum is light, it’s easier and cheaper to ship. You can package and load more pieces on a lightweight pull-behind trailer for your contractors.
The decision to use aluminum versus steel depends on the project, whether it’s industrial, commercial, or residential. Aluminum is strong, contrary to what a lot of people think. In Miami-Dade County in Florida, where they test and certify all the roofing structures for hurricane conditions, aluminum panels typically are equal to or slightly outperform steel roofing panels. There are a lot of advantages to aluminum, but It’s not always the best or right material to use, depending on the size of the building, load, etc. For structural products and long-run, low-slope roofing projects, steel is still the go-to choice.
Aluminum’s Versatility
As mentioned previously, the ability of aluminum to be reshaped makes it an excellent choice to be embossed. There are about five different patterns of embossing that look great on both mill finish and pre-painted aluminum in prints, patterns, or solids. Many high-end residential roofing shingles are now made of aluminum with multicoat woodgrain prints. It can be heavily worked without fracturing, which is difficult with light-gauge steel.
Aluminum’s smooth, flat surface makes it excellent for prints and patterns, from camo, to a rustic look, to a traditional high-end wood grain. It’s available in a variety of colors and textures and any paint system available in steel is also available to be applied on aluminum.
A recent trend in residential applications is for all trim and accessories to match the roofing or wall colors. For years gutters, downspouts, soffit and fascia were different colors and many times just in white or off-white. Today, people want everything to match their roofs, walls, doors, and windows, so uniformity is becoming crucial. It creates a higher-end look. Yes, it creates more items for a builder to carry and inventory but also allows for more sales on value-added products.
Pros and Cons of Aluminum and Steel
Steel is best for industrial commercial buildings because it allows a longer span between structural frame members. But using aluminum in smaller buildings (such as sheds) can save a lot of metal because it doesn’t need to support as much weight for the roof, walls, interior ceiling panels, liner, and other areas. One downside of aluminum is that it’s more susceptible to hail damage, so it’s not good for roofing products, especially in the hail belt. It’s much better for trim accessories or higher-slope applications.
Both aluminum and steel are fire resistant and are energy efficient and recyclable. However, aluminum will expand and contract, so aluminum shouldn’t be used for exposed fastener roofs because it expands and contracts too much with temperature changes. It makes a great choice for concealed fastener roofs. For corrosion resistance, aluminum is superior to steel on the surface and at exposed sheared edges, as aluminum is a pure solid alloy.
Conclusion
While steel has been a mainstay in post-frame construction for decades, aluminum is gaining traction in the industry. With its cost effectiveness and its ability to be matched and blended in with its steel counterparts, it’s destined for growth in this market! RB
Steve Swaney is a sales business development specialist for Mid South Aluminum www.midsouthalum.com. The company, headquartered in Jackson, Tennessee, is an aluminum distributor that specializes in pre-painted aluminum building products. This article is based on Swaney’s presentation of this topic at Shield Wall Media’s Post-Frame Building Show in Branson, Missouri, June 19-20, 2024.