Lightning and Metal Roofing: What You Need to Know

Published October 27, 2014 by Whirlwind Team

lightning and metal roofsWe can wax poetic all day long about the benefits of metal roofing products, but most clients boil all that information down to a single question: What about lightning? Isn't metal roofing dangerous?

The short answer: No, it's not. Metal roofing is perfectly safe. It does not attract any extra attention from lightning and, just like buildings constructed with traditional building materials, any electricity from a lightning strike will will be safely transferred to the ground below so occupants will be unaffected. Plus, metal's inflammable nature means your home will be even more safe should the rare chance of a lightning strike actually take place.

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Protect Your Building From Lightning Strikes With a Metal Roof

The concern about metal roofs attracting lightning strikes is most likely associated with the fact that metal can be an electrical conductor. Even so, metal roofs do not attract lightning and are not struck any more frequently than other roofing materials.

Lightning is attracted to:

  • High points
  • Thin points
  • Structures that cover a large area of ground

So, the likelihood of a lightning striking your home, business or agricultural building depends on its height and size rather than the building materials you use. And, in fact, there is currently no known material that can be used to decrease the likelihood of a strike.

What can be done is to decrease the potential for structural harm in the event that your building is struck. Fire is the most destructive element of a lightning strike because most roofs will immediately combust. In this regard, metal building materials far exceed traditional wood framed buildings due to metal's non-combustible nature.

Should your metal roof be struck by lightning, the electricity will be spread out across a larger area, which diminishes the immediate impact. Then, the metal's fire-resistant properties will protect your building even further.

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Metal Roof or No - These Building Strategies Decrease Your Chances of a Strike

By evaluating what factors increase the chances of a lightning strike, you can plan your site location and building strategies accordingly. Here are some things to consider:

  • Topography. Lightning is attracted to high points. So, if your property has a combination of hills and flat lands, the buildings on the hills - the high points - will be more prone to lightning strikes than those in the low-lands. Keep this in mind when you are scouting out potential building sites. That being said, lower-lying land doesn't drain as well and your likelihood of weathering wet years is significantly greater than the likelihood of a lightening strike, so keep that in mind.
  • Size and expanse. The taller and/or more expansive the building is, the more likely it is to be struck. This may or may not alter your current building plans depending on where you live. Again, lightning doesn't strike buildings often and as long as your metal roof is tied to the ground via a strap and/or lightning rod like any other roof, you should be fine.
  • Proximity to other geographical features. If your building is smaller than the buildings and geographical features around it, like trees or rock outcroppings, it will be the least-likely target during a storm. On the flip side, if you have the tallest building on the horizon, your building might be the target before other, lower-profile features.
  • Frequency. Obviously, if you live in an area that is prone to thunderstorms, your buildings (along with everyone else's in the area) - will be more prone to strikes.

Building With Metal Decreases Your Chances of Lightening-Related Structural Damage

So, there are things you can do do decrease the potential of a lightening strike, but once your building is struck, it's structural integrity and the safety of the occupants depends largely on the materials you have built with. This is where things get a little more interesting. Remember that we started by saying people get confused, thinking that because metal is a conductor, it is a less safe roofing material? In fact, the exact opposite is true.

Because metal is a conductor, it spreads the force of the electricity out, rather than concentrating it all in one place. This helps to diffuse the full impact of the strike. The electricity will travel almost instantly through the conductive material(s) to the ground. The average lightning flash only lasts about 30 microseconds. If your building materials are combustible, the results often include a destructive fire. By building with steel and metal building products, and pairing them with other fire-resistant materials, your building is more likely to withstand a lightning strike than the rest of the wood-framed buildings in your neighborhood.

Contact Whirlwind Steel to learn more about metal roofing and other building materials.

Metal Roofing Guide

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