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Choosing the correct metal roof material based on your geographical location.

Having a new metal roof installed is a major investment, but should never be a risk. Did you know… Installing the incorrect material/panel combination can give you less than half the lifespan of a correctly installed shingle roof. However, if done properly, by a professional, with the right materials, then its probably the last roof you put on that house.

A metal roof has plenty of benefits aside from it’s beautiful aesthetics, but once again without the proper materials and installation, not only will you be replacing your roof a lot sooner than you should, but you won’t benefit from some of the key features a metal roof has to offer, as discussed here.


Don’t feel like reading…

Go ahead and scroll to the bottom to find out which material best suits your needs. If you need help just contact us to speak to a professional.

The reason I’m writing this post is, because whether we here at Summers Roofing or someone else installs your metal roof, I think everyone deserves to be knowledgeable about the product they are investing their hard earned money in and the realistic expectations of that product. As an industry professional it’s our responsibility to be educated and recommend the best products, based on geographical location, warranties, prices, etc., so that you don’t have to be. Unfortunately, we all know that some people use the term “professional” lightly. Having to explain to a homeowner that the metal roof they thought was lifetime with minimal to no maintenance is in fact not true, because of the product or workmanship, that’s one of the hardest things I’ve had to do in my professional career. So don’t be afraid to ask questions, protect your investment.


  1. First, let’s have a look at the most common residential metal roofing substrates…
    • Galvalume
    • Aluminum
    • Copper
  2. Paint finishes, this is very important, I will explain below.
    • Clear Acrylic
    • Siliconized Modified Polyester (SMP)
    • Kynar 500®
  3. Now, the most commons styles of residential roof panels, there are different variations of each style as we will discuss in a future post.
    • Standing Seam; 12″-16″ Wide; Concealed Fasteners
    • 5-V Panels; 21″-24″ Wide Exposed Fasteners
    • Corrugated; 36″ Wide; Exposed Fasteners; This category includes panels such as, Master-Rib, R-Panel, Rib-Lock, etc..
  4. Finally, lets look at what you’ll need to consider…
    • Proximity to salt water.
    • Extreme temperatures.
    • How much pitch is on the roof?
    • Regularity of hail storms.

Substrates

So, what exactly is Galvalume? Well according to Englert® Inc. “..consisting of steel coil coated with a metal alloy. That alloy is 45% zinc and 55% aluminum and looks similar to galvanized steel, but the visible crystals are smaller and close together, giving it a smoother appearance.” Galvalume is the most economical and can be used with any of the three major panel types listed above, however even at 55% aluminum it will still rust if installed within close proximity to salt water. I explain in greater detail below. Most commonly Galvalume is offered in three gauges, 24ga., 26ga. and 29ga. Most of the time the overall deciding factor on gauge comes down to what panel profile you decided to go with. For example; 26 and 29 gauge are a bad option for a standing seam panel, because it’s flat for 16 inches down the middle of every panel, so the thinner material would cause a rippling look (Oil Canning). This is intensified with every imperfection in the roof decking and is unavoidable with using the wrong materials and sometimes when using the correct materials, depending on the condition of the existing roof decking.

Aluminum on the other hand will never rust, making it not only the best option, but other than copper the only option if you live on the coast. Salt air can corrode thinner gauge aluminum but not rust. You want to make sure you are using at least .032 or .040 thickness with a Kynar 500® finish standing seam panel to ensure you are installing the correct material on your coastal home. Different manufactures have different warranties, but a good rule of thumb is to use aluminum within 1 mile of any salt water including brackish. Believe it or not some manufacturers don’t even warrant the substrate, only the paint finish, and even then have disclaimers in the paint warranty that if the wrong material is used it will void the warranty. I’ve even seen some that won’t warranty the finish on any material within 1500 ft. of a salt water environment. This happens because even though the material wont rust on the face of Galvalume, due to the Kynar 500® finish, creep rust will start on the edges of the panels and trim where they are machine cut with no paint finish. Eventually causing the paint to look like its bubbling, but it’s due to the rust in between the finish and primed back. With the cost difference being literally pennies on the dollar, please make sure you don’t risk it and if you live near the coast use a standing seam aluminum panel. I can not stress enough how important this is.

Copper, I’m not going to talk much about copper, obviously copper can be used pretty much anywhere. As the price tag suggests it’s the best material you can use for any of your roofing needs. However, I would not recommend using it with an exposed fastener panel, your material would outlast your panel profile with required maintenance. Whereas a Standing Seam panel will be lifetime with limited to no maintenance required.


Paint Finishes

Clear Acrylic, also referred to as Mill Finish, is only available in Galvalume panels. Mill Finish aluminum is available, but due to the protective oils in it, it can’t be coated in acrylic. Raw aluminum will turn a chalky white color when exposed to the elements, making it a bad option for any type of roofing panel. Mill Finish Galvalume panels with an acrylic coating are also cheaper than Siliconized Polyester or Kynar 500, making it a good option for a lower cost metal roof in areas at least 1 mile or more from salt water.

Siliconized Modified Polyester, have you ever seen a metal roof where the paint was flaking off, chipping or just fading very badly? Then I’m 98% sure you were looking at an old Siliconzed Polyester paint, this was before the new chemical solution now referred to as SMP or Siliconized Modified Polyester. SMP is an improved product but still doesn’t have the lifespan of Kynar 500®, based off of their limited warranty information available. SMP is used more frequently on 5-V and corrugated panels such as, Master-Rib, Rib-Lock, etc., that are considered lower cost / lower lifespan panels. If you are using an exposed fastener panel, in a place with fairly mild summer and winter months, away from salt water, then an SMP finish would be a good option to help keep cost down and still get the full lifespan of your expected metal roof.

Now, Kynar 500® and why you should always use it if your using Standing Seam. If your still reading this post, then your obviously seriously considering a metal roof and know that its no small investment. Always make sure your paint finish is expected to last as long as your actual panel material. I’m not sure if you’ve ever seen a metal roof that the paint was failing on or just faded badly, but I can promise you its not pretty, and can even lower the value of the house. If you are truly looking for that one and done metal roof with minimal to no maintenance then a Standing Seam panel, with a Kynar 500® finish is the best way to go, and the most bang for your buck. Most metal manufactures Kynar 500® paint warranty is 35 years.

Kynar Vs SMP
Photo Credit: McElroy Metal
Siliconized Polyester
Photo Credit: Sheffield Metals

 
 
 
 
 

 
 


Panel Profiles

Standing Seam panels are offered in several different variations with the most common for residential being a “1½” Standing Seam Snap Lock” panel. These panels are the only ones that are attached with a concealed fastener, meaning no maintenance on the screw heads that you would have with an exposed fastener panel. Also, allowing it to properly move when expanding and contracting due to weather conditions. Because of the unique way a standing seam panel locks onto the drip edge, it has the highest wind lift rating of any other panel type. A standing seam panel is best used with Aluminum or 24 gauge Galvalume and provides the most maintenance free metal roof system available. Due to the longevity of a standing seam roof, you should only consider a Kynar 500® paint finish, to ensure you paint lasts as long as your material.

Drip Edge Locking Detail
Drip Edge Locking Detail

Snap Lock Panel Detail
Snap Lock Panel Detail

 
 
 
 
 
 
 
 

5-V panels are an exposed fastener panel, usually 21″-24″ wide. Unlike standing seam, 5-V does not lock onto the drip edge, it overhangs approximately 1-1½” with screws close together at the bottom. This design doesn’t allow it meet the same uplift ratings, therefore coastal areas and other high wind areas are not a good location for 5-V panels. Which leads me to my next point. If you have determined that you are going to use aluminum, for whatever reason, I would strongly recommend using a concealed fastener standing seam panel. I’ll tell you why, aluminum is designed to be a lifelong product, standing seam metal is designed to be a lifelong product, but their only as good as the paint finish. Now you see why I said how important the correct finish is, and why one cost considerably more than the other. With that being said 5-V is offered in aluminum, so you might be thinking, “why wouldn’t an .032 aluminum 5-V panel with a Kynar 500® finish be considered as good as a standing seam panel?” Here’s why, because of expansion and contraction. This is why the flexibility of the paint is so important. Metal expands when it gets hot and contracts when it get cold, that’s just science and no manufacturer is going to change it. Well when you fasten that metal down with four screws every 18″ to 24″ apart it doesn’t allow it to move freely. This eventually causes the screw holes in the metal to become larger than the shaft of the screw itself creating leaks, and with approximately 3,000 screws on an average home there is no way to pinpoint exactly which one is the problem. This is where the maintenance on exposed fastener panels come in, you will have to eventually replace the majority of the screws with ones slightly larger at lease once possibly twice in the lifespan of the roof. This can also cause the panels to start developing a rippling effect and can eventually crack the paint depending on the finish.

Now I’m not saying there’s never a good time to use a 5-V panel. Like I said in the beginning, this is to make sure that you know exactly what product your getting and the realistic expectations of that product. 5-V is still a great product, mostly available in 24 gauge and 26 gauge Galvalume, in Kynar 500® and SMP finishes. The industry standard fastener is a matching 1½” screw with a neoprene washer for a watertight seal, this allows the system to still maintain a high enough uplift rating to be used in most areas. I apologize for not having exact numbers to be able to compare, but most of the time metal roof systems are engineered on a case by case basis. This tells you how far your fasteners should be to achieve the required uplift rating. So when might a 5-V roof be right for you? If you live far enough away from salt water to comfortably use Galvalume, you want to save some money but still increase value of the home, you don’t live in an area with extremely cold or hot months that will increase the rate of expansion and contraction requiring faster repairs. Or maybe you just don’t want to fully invest in a standing seam roof, because you don’t know how long you will live there. I would comfortable recommend 5-V in any of these situations.

Screw Pattern
5-V Screw Pattern

5-V Roof Panel
5-V Roof Panel

 
 
 
 
 
 
 

Corrugated panels are actually a style of panel, though in this post when I refer to the term corrugated I’m referring to any 36″ wide or larger, 26 or 29 gauge Galvalume panel. To name a few, Master-Rib, Rib-Lock, R-Panel, etc. Everything I mentioned in the section above about 5-V panels pretty much applies to corrugated panels, other than most corrugated panels are made of 29 gauge Galvalume and aren’t even offered in aluminum. The fasteners, screw patterns, trim profiles and accessories are very similar to that of a 5-V roof system, resulting in labor warranties usually being about the same for each. Like I said most corrugated panels are 29 gauge with a Siliconized Modified Polyester finish, and usually the labor for install is less expensive because of the coverage being wider and the material being lighter and easier to work with. This makes corrugated a great cheaper alternative than 5-V in most cases while still carrying the same labor and material warranties and raising the value of your home.

Profile Examples
Different profile examples

Union Corrugating Profile
Union Corrugating Profile

 
 
 
 
 
 
 


What you’ll need to consider

Proximity to salt water, I cannot stress enough how important this is. As I mentioned in the Aluminum section above, if you are close to a salt water environment including brackish waters and you do not use aluminum, it will rust, and have no material warranty from the supplier. No matter what the panel profile or paint finish, Galvalume and Galvanized will rust at an extremely accelerated rate within approximately 1 mile from any salt air. You will hear people say between 1,500 feet and 1 mile, I personally always go by one mile, because for pennies on the dollar, is it really worth the risk? About five years ago a call came into our office, the homeowner claimed her roof was literally rusting off of her beach house. So I went out to meet her and the whole time I already knew that in order for that to be possible the roofing contractor had to have installed the wrong material, I was just hoping it was only on a small section or she was mistaking what she was seeing. Unfortunately, after a very hard conversation I learned the roof was only 3 years old, and had cost her around $40,000.00 from a licensed roofing contractor. It was a 24 gauge Galvalume Standing Seam roof, and actually installed very well, just the wrong material. Before when I talked about creep rust, it had started at the edge where the panels and drip edge were factory cut and completely deteriorated all the drip edge and where the panels lock onto it, all the way up the roof a few feet on every panel. Every time the wind blew the bottoms of the panels would just flap, she had to replace the entire roof. So yes, unfortunately this means if you live close to the ocean the only real metal roof option for you also happens to be the most expensive, but also the best. There is no visual difference in Galvalume and aluminum, so always remember, a magnet wont stick to aluminum, but it will stick to Galvalume and galvanized. So make sure your getting the materials you paid for.

Panel Rust
Photo Credit:
TheRoofDuck.com

Roof Rust 2
Photo Credit:
TheRoofDuck.com

 
 
 
 
 
 
 

Extreme temperatures. The biggest reason this is important is because of expansion and contraction, I wouldn’t recommend using any exposed fastener 5-V or corrugated panels in areas that has extreme temperature changes as this can increase the rate at which fixed fastener screw holes become potential leaks and in some cases even begin to back the screws out of the decking. Also, areas that get a lot of snow sitting on the roof for long periods of time can begin to accelerate rust around screw heads and factory cut edges. The screw heads can actually act as grip for snow and prevent the roof from self cleaning itself the way a standing seam panel might. On the other hand, if you live somewhere that has very hot summer months, your style of panel may not matter as much as the finish. Many if not all manufacturers offer most of their products with an energy star efficiency rating. If roof temperature is one of your concerns make sure you are using an approved energy star partner.

Roof pitch only matters if you are dealing with very low slopped areas. Your roof can be to flat for any type of metal panel under certain circumstances, but under other circumstances you can install certain panels on a completely flat roof. On any roof area that has less than a 2-12 pitch I would recommend consulting a roofing professional to determine the best panel on a case by case basis.

Do you live in a High Hail Area? Let me quickly touch on when a 29 gauge Galvalume, SMP Finsih, Corrugated roof could be the best metal roof option for your house, even over .032 aluminum. If you live in a high hail area, but still far enough away from salt water, then this may be the most sensible panel to use. Here’s why, on shingles hail can actually cause cracking and breaks, resulting in potential leaks meaning the integrity of the roof has been compromised. However, on a metal roof, most of the time hail will only dent the roof badly but not compromise the integrity of the system itself. See where I’m going here, so you could very well be stuck paying for the replacement out of pocket or having live with a very cosmetically damaged roof. Thankfully, where our company is located we are not considered a high hail area according to Weather.com

Hail Map
Hail Map

Metal Choice Tool

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