Many home and building owners believe metal roofing systems attract lightning strikes and are easily damaged by hail. Like the assumption that metal roofs are noisy when it rains, these beliefs are misconceptions. The facts paint a much different picture—mainly that metal roofing systems can endure various forms of extreme weather.
They can withstand windspeeds of up to 120 miles per hour and shed snow quickly. Metal roofing systems can also provide a high-level of protection against hail damage and do not factor into the likelihood of a lightning strike. In fact, with proper preparation, they may even help reduce damage caused by lightning.
Let’s explore how metal roofs can provide buildings with a safe and durable covering no matter the weather.
Lightning is the rapid discharge of atmospheric static electricity. Since most metals conduct electricity easily, it seems to make sense that a tall structure with a conductive material at its topmost point would attract lightning strikes from passing clouds.
Though this seems intuitively correct, the truth is a bit more complicated. According to roofing experts, when lightning is discharged into the ground, it will seek the path of least resistance. Since air is a relatively poor electrical conductor, this path is often the tallest thing around. If a tree is taller than a building, then lightning is more likely to strike the tree, even if the building has a metal roof. The same can be said for other buildings. A taller building with a shingle roof will be struck with lightning more regularly than a smaller neighboring building with a metal roof. According to the Metal Construction Association, a building’s surroundings (hills, trees, or taller buildings) play the largest role in estimating the likelihood of a strike—building material has not been shown to be a significant factor.
What happens after lightning strikes is more interesting. Highly conductive materials allow the smooth passage of electrical currents, and poor conductors can convert electricity from a lightning strike into heat, which can result in fires or an explosion. This is why trees tend to split and catch fire when struck by lightning. On their own, the metal roofing panels offer a low-resistance path between the sky and the ground—potentially reducing damage if a building is struck by lightning.
This protection is bolstered when metal roofs are paired with a lightning protection system (LPS). In fact, the National Fire Protection Association (NFPA) 780 standard recognizes that the material’s non-combustible nature can mitigate damage caused by lightning. This is because metal roofs efficiently conduct the lightning’s electrical energy from the strike point to the LPS’s wire that leads to the ground rod.
Hail affects roofs of all materials, so it’s a concern for new projects and rebuilds alike. While other types of damage can be easily spotted and taken care of, hail can cause tiny perforations in most roofing systems where water can seep in later and cause hard-to-see damage.
Like other weather, the risk hail poses to the roof depends on several factors such as the size of hailstones and the duration of the storm. The slope of the roof can also determine the risk of damage. Larger stones and longer storms can cause more damage. Likewise, flatter roofs will be damaged more than sharply pitched ones.
Outside of those factors, roofs that have high impact resistance will provide the most protection against hail damage. Metal roofing installed over a solid substrate often achieves the highest rating, Class 4, from the Underwriters Laboratories (UL) 2218 impact testing standards. Class 4 materials resist damage from two-inch diameter steel balls dropped from 20 feet. The roofing assembly will only pass if the surface material shows no sign of penetration. This means most metal roofs can provide substantial protection from hailstones. Moreover, unlike other roofing materials, metal roofing panels retain their impact resistance over the course of their service life.
Because of their long-lasting weather resistance, Drexel Metals roofing systems may even reduce a homeowner’s insurance premium.
Whether it’s high winds, snow, hail or lightning, a metal roof can withstand the elements with less damage than other roofing systems. All across the country, from Boulder, Colo., to central Florida, homes and commercial buildings have used metal roofing systems to provide long-lasting strength and durability to a structure.
In addition to their strength, Drexel Metals offers several warranty options that can match the needs and scope of most projects. These options give home and building owners peace of mind that their system will stay functional and beautiful year after year.
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