AIA Course Number: SMINC00520
Credit: 0.25 LU/HSW
Learning Objective: After successful completion of this learning program, you will be well-versed in the five metals typically specified for metal roofing and their advantages and disadvantages as appropriately chosen building materials.
Please Note: After watching the video and reading the text, click the button at the bottom of this page to take the quiz.
Whether you’re an experienced architect or new to the industry, it’s vital to know the advantages and disadvantages of the different metal roofing materials that you can specify for your projects.
Five of the most common materials used in metal roofing are Galvalume®, aluminum, zinc, copper, and stainless steel. Let’s dive deeper into the attributes and uses for each material.
Bethlehem Steel introduced the Galvalume coating to the construction industry in the early 1970s. Galvalume roofing material combines three of the most important metals used in roofing today—steel, aluminum, and zinc. Manufacturers begin with a carbon steel base sheet, which is then continuously hot-dipped with aluminum and zinc alloys until it reaches a coating consisting of 55% aluminum, 43.4% zinc, and 1.6% silicone over the base metal to protect it from the elements. This system allows for one material to have some of the best characteristics of each included metal—making it one of the fastest growing materials in today’s metal roofing market.
Pros of Galvalume Roofing
COLOR OPTIONS – One of the most appealing aspects of Galvalume roofing is the fact that it can come in an array of different colors. These pre-painted options allow for more versatility when architects are in the design phase.
LEAST EXPENSIVE – Compared to other high-quality metal roofing materials, Galvalume costs the least amount of money. Depending upon the thickness, color, and quality of the desired Galvalume panels, pricing could range anywhere from $75 to $250 per roofing square (100 square feet).
CORROSION RESISTANT – Galvalume is designed to combine the toughness and strength of zinc with the rust-resistance of aluminum. Testing in the field indicates that Galvalume roofing could last as long as 60 years without any extreme signs of corrosion.
EASY TO FORM – Galvalume is an ideal material for rollforming and panel forming, making it easy for contractors to make any profile for any project.
RECYCLABLE – Galvalume is 100% recyclable, meaning that any scrap metal left over from a job or old metal roofing that has been replaced can be easily recycled.
INSTALLED OVER EXISTING ROOF – One of the major benefits to choosing Galvalume is the fact that it can be retrofitted or re-roofed over an existing roof, meaning no tear-off cost is required.
WARRANTIES – Many companies that sell Galvalume coils, sheet metal, or processed roofing panels offer warranties with their products. These warranties can be anything from paint warranties, Weather-tight warranties, and labor warranties. Always make a note to ask about warranties that are available when purchasing a metal roof.
Cons of Galvalume Roofing
OIL CANNING – Oil canning is an inherent characteristic of light-gauge, cold-formed metal products, especially products with broad flat areas. It is a visual phenomenon seen as waviness or distortion in the flat surfaces of metal wall and roofing products. Oil canning is subjective and normally only an aesthetic concern that does not affect a product’s strength or performance. This occurrence is a possibility for any kind of metal roofing or walls, including Galvalume. But there are methods to minimize the appearance of oil canning, including:
- Hiring an experienced contractor who knows the best methods to reduce oil canning, including:
- Panel thickness
- Appropriate panel spacing
- Deck or other supporting structure is in alignment
- Buying trustworthy brands of coil
- Using striations or rib rollers in the flat area of the panel to minimize the appearance of oil canning
FADING/CHALKING – One drawback to painted Galvalume is the fact that the color will fade over time due to sun and UV exposure. There are ways to slow down this process, most of which depend on the resin or paint coating used on the metal. Kynar painted systems have the most fade-resistant coatings, followed by silicone-modified polyester (SMP) and polyester systems. Also, painted Galvalume could be susceptible to chalking, a whitish residue visible where the coating is present. Again, it’s important to pick the coil with a tested and proven chalk rating.
INTERACTIONS WITH OTHER MATERIALS – Galvalume performs best when not in contact with other materials, such as iron, copper, concrete, bricking, and treated lumber (decks). Contact with or galvanic reactions to these substances could result in quicker corrosion or complete failure of the Galvalume roof panels.
Aluminum is one of the most predominant and popular metals in the world, mainly because of its use in the canned beverage industry. But aluminum, the third most abundant metal on Earth, spans way beyond this scope and makes a great material for the metal roofing industry, especially for projects in sea and saltwater environments. Not only does aluminum stand up to extremely harsh weather conditions, but it’s one of the most sustainable metals in the world, which is why it’s become such a popular roofing choice for structures.
Pros of Aluminum Roofing
HIGHLY RECYCLABLE – Nearly all metal roofing is recyclable in one way or another. The best part about aluminum is the fact that about 95% of all aluminum roofing installed across the world is made from recycled aluminum materials. Sustainability in construction has become vitally important in the past 20 to 25 years, which is why the use of aluminum roofing is becoming more common.
LIGHTWEIGHT STRENGTH – Aluminum sheet metal is very lightweight and easy for a contractor to form and install. Even though aluminum is a thinner and lighter material, it’s still very durable and can replicate the strength of much thicker metals.
NO RUSTING/CORRODING – One of the biggest selling points of an aluminum roof is the fact that it doesn’t have red rust and corrosion is generally minimal as it ages. Studies have even shown that aluminum can work great in coastal areas with high rainfall and seawater spray conditions. Aluminum performs better in coastal environments than Galvalume or other steel materials.
MEDIUM PRICE POINT – Aluminum is in the middle range when it comes to material cost. Aluminum is cheaper than both zinc and copper with a price point of about $200 to $575 per roofing square depending on thickness, finish, and panel type.
READILY AVAILABLE – As mentioned before, aluminum is the third most abundant element in the Earth’s crust, making it an ideal material for structural applications. Unlike a more restricted material such as copper, it’s not difficult to come by aluminum roofing and contractors who know how to install it.
Cons of Aluminum Roofing
NATURAL COLOR – Using aluminum roofing in its natural color (silver/gray) isn’t recommended by too many architects and installers. As the metal ages and undergoes weathering, it doesn’t hold its original color and often becomes washed out and spotty. The best way to overcome this issue is to buy resin coated roofing coils or panels, which will age much cleaner over time.
DENTING – Since aluminum roofing is frequently a thinner, more lightweight material, it has been known to dent easier than other metals. If a structure is underneath trees or any other object with something that could fall on the roof, another type of metal material may be a better option.
THERMAL MOVEMENT – Aluminum expands and contracts roughly twice as much as a steel roof. This generally means you do not want to “double pin” the panels if they are in lengths greater than 20’. This expanding and contracting can also cause oil canning, increased noise, and more required maintenance on exposed fasteners.
Among contractors and architects, zinc’s popularity in metal roofing projects has experienced a steady increase in the United States because of its ease of use, immunity to corrosion, and other sustainable features.
As the 23rd most abundant element in the Earth’s crust, zinc paneling and coils are easy to come by in the metal roofing industry. In fact, natural zinc production within the Earth is on the rise, which means there is more of the metal available for extraction and use in the industry.
Pros of Zinc Roofing
LONGEVITY – Zinc roofs have been known to last anywhere from 60 to 100 years. Studies have shown that in some cases zinc roofing could last up to 150 years depending upon the quality of installation, building properties, and climate.
ECOFRIENDLY – Since zinc is a natural metal extracted from the ground, zinc’s toxicity levels are very low, even after fabrication. Property owners don’t have to worry about any toxic run-off or ground pollution surrounding their zinc roofing. Additionally, zinc is a non-ferrous metal, meaning it does not contain iron, and therefore requires less energy to manufacture.
ENERGY SAVINGS – Metal roofing in general cuts down on the cost of heating and cooling because it reflects the sun’s heat that is normally absorbed by asphalt shingles, tiles, etc. Using coated or uncoated zinc roofing material helps reduce the amount of energy absorbed into a building.
SELF-HEALING – Zinc possesses its own outer protective layer, which prevents against corrosion, scratching, and panel markings. If wind or another element were to scratch the surface of the zinc roof, the metal’s protective layer would fix and correct itself over time.
EASY MAINTENANCE – Zinc’s self-healing properties often means the building owner doesn’t have to perform any routine maintenance to the roof. It’s often said that zinc roofing is the “install and forget about it” option to metal roofing.
Easy to Form – Architects and contractors often use zinc in their projects because it’s a softer metal and can be easily shaped into different profiles for rollforming, gutter forming, and seam creation.
Cons of Zinc Roofing
EXPENSIVE – The most prominent drawback to zinc roofing is the price. While there are many variables that factor into determining the price, zinc roofing can cost anywhere from $600 to $900 per roofing square. When selecting the best roofing, keep in mind that metal roofing lasts decades longer than asphalt roofing and requires less maintenance and replacement.
OIL CANNING – Like any metal roofing, zinc metal roofing could be subject to oil canning.
UNDERSIDE CORROSION – If the zinc roofing is improperly coated on the underside of the panel, corrosion could take place. This occurs when water molecules get trapped underneath between the panel and the insulation or underlayment, which can cause the metal to weaken if not coated
VENTILATION – All zinc applications require adequate ventilation to help the system from failing from the inside (or underside) out. Above deck ventilation products combined with using the appropriate details will contribute to the longevity of a zinc system. The correct ventilation process for zinc roofing is more of a precaution than a disadvantage.
The use of copper roofing has been around for hundreds, if not thousands, of years. Historical data shows that the Romans actually used copper covering on the roof of the Pantheon in 27 B.C. To this day, many large architectural structures, commercial buildings, and even residential homes have roofing made from or accented with copper panels and coils.
Pros of Copper Roofing
LIGHTWEIGHT – Compared to different metal substances and other roofing materials such as shingles, concrete, or tiles, copper is extremely lightweight. Not only does this make it easier for installers and contractors to work with, but it also puts less stress on the structure over time.
ENERGY-EFFICIENT – All metal roofing is energy efficient and can help cut down the cost of energy bills.
DURABLE – Copper is a durable element and can withstand numerous decades as a roof. If properly installed, copper roofing can last 100+ years in some instances. Copper also works well in locations with heavy snow, frequent rainfall, and strong winds.
AESTHETICALLY PLEASING – Copper is often referred to as a premium roofing material, as it enriches the outside of a building and adds a metallic reddish-brown focal point to a structure. As the copper ages over time, it develops a blue-green covering called patina, which happens because of oxidation and sun exposure. Many building owners specifically buy copper because of the way it ages and adds to the curb appeal of a structure over time.
RECYCLABLE – Though not as recyclable as zinc, copper can also be recycled and reused if still in good condition. Copper is also a naturally sourced metal and can be used in its original mined metallic form.
SOLDERABLE – Copper can be soldered, unlike other roofing materials. This means that roof and wall flashings, as well as gutter joints, will be weather-tight with a soldered connection.
Cons of Copper Roofing
VERY EXPENSIVE – Copper is one of the most expensive metal roof materials, as copper is not as abundant in the Earth. It can be anywhere from 4 to 15 times the cost of an asphalt roof but could last 100+ years with the proper installation and care. Currently, copper roofing costs about $500 to $1,000 per roofing square.
EXPANSION/CONTRACTION – In climates with striking differences in temperatures, copper roofing often expands and contracts during heating and cooling just like other metal systems. Care should be taken to ensure that your system will accommodate this thermal movement.
PATINA – Some people are drawn to the look of the patina that will happen on a copper roof, but there are those who might not want this greenish blue covering on their structure. There is currently not an exact science to the color or time frame patina will occur with copper. Also, in some climates the patina will turn a rich green and in other climates it will maintain a dark bronze look for decades.
RUN-OFF STAINING – Copper roof rain run-off has been known to stain siding, brick, concrete, other metals, wood, etc. It’s important for architects to be aware of this factor and make sure the roof is installed in a way that the water can safely run off without encountering other stainable materials. If this does happen, there are many different methods to help remove copper run-off staining as well.
Stainless Steel Roofing
Another metal that is popular as a metal roofing solution is stainless steel, a steel alloy made up of at least 10.5% chromium. When people think of stainless steel, they often think of large architectural structures such as elevators, bridges, building columns, handrails, etc. Above all, stainless steel is most notably known for its strength, making it a high-end metal that could be the right material choice for many projects.
Pros of Stainless Steel Roofing
DURABLE – As mentioned before, stainless steel is used in some of the most powerful and sturdy metal products in the world. Because stainless steel can withstand corrosion and degradation for 60+ years, it makes a great choice for metal roofing.
WEATHERS ELEMENTS – Stainless steel is specifically designed to withstand extreme weather and temperature climates. In addition to efficiently reflecting thermal temperatures, stainless steel also doesn’t become brittle or crack during cold temperatures and keeps the warm air from escaping a structure. Some stainless steel items can even be installed in coastal environments.
EXPANSION/CONTRACTION – Another reason stainless steel is a great option for locations with extreme climates is because of its low thermal expansion properties, meaning the metal won’t expand or contract due to temperature fluctuations.
WARRANTY – Many companies offer warranties for stainless steel metal roofing because it’s expected to last for long periods of time. Always be sure to check with the manufacturer if warranties are available.
FINISH OPTIONS – Stainless steel comes in a variety of different finishes, which makes it easier to match a multitude of other building materials. It can range anywhere from a dull, subtle gray similar to zinc roofing, to a highly reflective, polished finish resembling a mirror.
Cons of Stainless Steel Roofing
EXPENSIVE – The cost of stainless steel is in line with the price of zinc and copper, making it a high-end metal roofing choice. Currently, stainless steel roofing can cost anywhere from $400 to $1,200 per roofing square depending on the finish, panel type, and thickness.
STANDING WATER – Roofing made with stainless steel, especially if it’s in contact with other non-stainless steel metals, requires adequate draining methods in order to remain durable and functional. Too much standing water on stainless steel can act as an electrolyte and cause galvanic corrosion of the metal.
Galvalume, aluminum, zinc, copper, and stainless steel are all great solutions for metal roofs and walls. Knowing the common and unique aspects of a structure, residential or commercial, is the best place to start when choosing the best material. Then, determine what factors are important to your project, including:
- Material strength (consider the climate, UV/weathering exposure, snow, rainfall, etc.)
- Weight your structure can withstand
- Energy-efficiency and recyclability
- Materials the roof or water run-off will encounter
- Availability of materials
(NOTE: It’s critical to check and make sure that any materials touching or situated at a run-off point of the metal system are compatible with the type of roof or wall metal substrate. Galvanic reactions can severely degrade a system and can lead to premature failure, which is why similar and dissimilar materials should always be verified beforehand.)