Will Metal Roofs Attract Lightning?

Metal Roof Lightning Blog Cover

Will metal roofs attract lighting? No, having a metal roof should neither increase nor decrease its chances of being struck by lightning. Other factors like building height, size, and topography do, however, have an influence.

The Metal Construction Association has even pointed out that metal roofing may actually keep your building safer in the event of a lightning strike.

A Common Question

Installing a metal roof onto your commercial building can have a number of benefits. It is one of the most durable roofing systems available today, meant to last for decades. But the benefits of metal roofing systems are meant for another article.

The question that just about anyone asks is whether or not that metal roof is dangerous when it comes to attracting lightning. After all, we have been told our whole lives that metal is a natural conductor for lightning, so that must mean that it’s dangerous.

The short answer is no, metal roofing is not dangerous and does not naturally attract lightning strikes. Generally speaking, metal roofing is quite safe. It holds no extra attraction to lightning. Like buildings that are constructed with traditional building materials, any electricity from lightning strikes will be transferred safely to the ground below, keeping the occupants inside safe.

Still, that does not mean that you shouldn’t take preventative measures to keep your building safe from lightning strikes with a metal roof. Here are some things that you need to take into consideration.

Will Metal Roofs Attract Lightning

Metal Roofs and Lightning

The concern of the uninitiated about what happens when lightning strikes metal is directly related to the fact that metal can act as an electrical conductor. Despite that fact, metal roofs absolutely do not attract lightning strikes. Not only that, they are not struck any more frequently than any other type of roofing material.

What is lightning attracted to? Thin points, high points, and structures that cover a large area of ground. That means that the likelihood of a lightning strike hitting your home or commercial business building depends on both the height and size rather than the materials that were used in the construction.

Speaking of material, there is currently no known material that can be implemented to decrease the likelihood of a lightning strike. You can, however, do things to decrease the potential for any structural harm to your building should the building be struck.

Fire is actually the most destructive element of a lightning strike. This is because most roofs will immediately combust. This is where metal frames actually come in handy. As far as building materials go, traditional wood is much more likely to combust than metal due to the latter’s non-combustible nature.

So, what happens when lightning actually does strike your metal roof? The electricity will spread itself out across a larger area. This diminishes the immediate impact of the strike. From there, the fire-resistant properties of the metal will help to further protect your building.

What Happens When Lightning Strikes Metal

Factors That Influence Commercial Roof Lightning Strikes

Since we now know what can increase the chances of a lightning strike, there are measures to be taken. If you are planning a new build, you can plan the building strategies and site location. Consider these factors:

Size and Expense

The more expansive and/or taller than a building is, the more likely that building is to be struck. Depending on where you live, this could alter your building plans. Since lightning doesn’t strike buildings often, and your metal roof is tied to the ground using a strap or a lightning rod like other roofs, you should be fine.

Topography

As stated previously, lightning is attracted to high points. If your property has a number of flatlands and hills, the buildings on the hills – which are your high points – will be more prone to those lightning strikes than any buildings that are in the low-lands. This is something to keep in mind if you are looking for a building site.

The caveat here is that lower-lying lands tend to not drain as well and you are looking at weathering wet years instead of a lightning strike, so keep that in the back of your mind.

Proximity to Geographical Features

If your building is smaller than geographical features, and buildings around it – like the rock outcroppings or trees – it will be the least-likely target when storms roll in. On the flip side, having the tallest building on the horizon will likely make your building a quite literal bigger target.

Frequency

This one should kind of go without saying, but if you live in an area that is more prone to thunderstorms, your buildings – and everyone else’s – will be more prone to potential strikes.

Factors That Influence Commercial Lightning Strikes Infographic

Metal Roofs Can Reduce The Chance of Structural Damage

As touched on in the section above, you can do several things to decrease the potential of a lightning strike. But when your building is struck, it can put the structural integrity of the building as well as the safety of the occupants at risk.

This is why having the right materials in place is essential. Again, people get confused since metal is a conductor, thinking that it makes for unsafe roofing material. But the fact of the matter is that the exact opposite is true.

Since metal is a conductor, it actually spreads out the force of the electricity rather than focusing it in one place. For this reason, the full impact of the strike will actually be diffused. The electricity from the strike will travel nearly instantaneously through those conductive materials straight to the ground.

Did you know that the average lightning strike lasts only 30 microseconds? If your building materials are more likely to combust, the results of a strike are more often than not a destructive fire. When using metal and steel as building products, and also pairing them with fire-resistant materials, your building will be much more likely to stand up to a lightning strike than those wood-framed buildings that permeate your neighborhood.

More About Lightning Strikes

Knowing more about this natural occurrence can help you better understand lightning strikes that occur in our lives. Lightning has been studied for hundreds of years now and we have a pretty good base of information about it. What is unknown is how it forms and where it strikes. This makes behavior unpredictable.

Lightning is actually a rapid discharge of atmospheric static electricity. As such, there are three major types of lightning strike that can occur: cloud-to-cloud (CC) discharges from a highly-charged cloud into a less-charged cloud; Intra Cloud (IC) discharges inside of a single cloud from a highly-charged area in the cloud to a less-charged portion in the cloud, and cloud-to-ground (CG) discharges from a cloud that is highly-charged down to the earth. We best understand CG and it is the type that we are most concerned with when it comes to property and life.

While there is uncertainty about where lightning discharges appear, the exact location depends on topography, geography, as well as movements from the storm. When lightning is ready to discharge, it simply will. This happens whether there is a roof in the area or not.

There is faulty logic at work in assuming that metal roofs attract lightning strikes in a similar way to a lightning rod. This is because lightning rods are not actually made to “attract” lightning. They are made to channel that lightning safely to the ground if and when a strike hits the building.

What you might not have realized is that any electrical charge, including lightning, seeks out the path of least resistance to discharge. With CG lightning, it is discharging into the earth. To get there, it has to move through an expanse of air.

Lightning Strike

Buildings and trees are better electrical conductors than air. A taller building provides a much easier path by shortening the distance that the lightning has to travel through the air. In the area where that lightning discharges, it will seek out the best conductor that is closest in location to the cloud.

It should go without saying that a tall tree is far more likely to be hit by a strike than a shorter tree that is next to it. A large or tall building is far more likely to be hit than a smaller or shorter one. The material covering the roof, as well as other structural materials, are most definitely not determinant factors for where the strike will be.

When the lightning has struck, however, it depends greatly on what the building is made of and whether or not it has a lightning protection system. Lightning can travel more easily through something like steel or copper than it would through something like concrete or wood.  Even though the latter is a poor conductor, it has more electrical resistance. This converts that energy into heat, which can possibly cause fires or even explosions.

Understanding what happens in the event of a lightning strike is far more important than the conducting ability of your roofing material. You can rest peacefully at night knowing that your metal roof is no more likely to attract a lightning strike than any other sort of material and that it can actually help prevent commercial roof fires and limit the damage.

So forget all the things that you learned about metals being conductors. That doesn’t apply here when it comes to keeping your building safe. The next time someone asks you: is it safe to be in a metal building during a lightning storm, you can point to the reports of it being safer than normal. However, it is important to keep in mind that a metal roof fire is still possible and to be vigilant in keeping your building safe.

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