In every aspect of our daily lives, a lightning strike on an occupied building is a concern not only for the electronics surrounding us, but for the risk of fire caused by that strike. Concern over the use of metal roofs in construction has raised the issue of whether metal roofs attract lightning strikes more than other types of roofing materials. Research has shown that the material used in roof construction does not influence the risk of a lightning strike. There are several other factors that may influence the risk of a lightning strike that will be discussed however the presence of a metal roof may actually be beneficial in a situation where a lightning strike has taken place.
The probability for a building to experience a lightning strike is influenced by a number of significant factors:
- Area Topography: The probability of a lightning strike is increased when the subject building is located on an elevated site such as a mountain or hilltop as lightning is drawn towards the highest object in a strike area.
- Height of the Building: A tall building, relative to other structures in the surrounding area is more likely to have a lightning strike than a building that is the same relative height as surrounding structures (buildings, trees, towers, etc.) The presence of a very tall structure in proximity to a small, short building will tend to reduce the likelihood of a strike to the small building.
- Size of the Building: While not necessarily the tallest structure in a strike area, those buildings covering a larger surface area provide a more accessible target for lightning strikes.
- Frequency/Severity of Thunderstorm Activity: Certain geographic areas are more prone to the development of storms that lead to lightning and lightning strikes.
Note that none of the significant factors above include the material used in construction of the roof. Metal roofs do not attract lightning strikes; nor do metal roofs protect a building against lightning. A metal roof is no more or less likely to get struck by lightning. Based on the factors listed above, the probabilities of a strike to a metal-roofed structure are no more or less than any other kind of structure, as these probabilities have to do with height and size of the structure and its surroundings rather than its construction materials.
SOURCE: Metal Construction Association
