Winter weather is not the only hazard chimneys face. A lightning strike during a severe thunderstorm can also damage the chimney. Since lightening only occurs during a thunderstorm, when you hear thunder you were within 25 miles of a lightning strike. The louder the noise, the closer you are to lightning.
More than 20 million lightning strikes are detected annually by the National Lightning Detection System (NDLS). A bolt of lightning packs a powerful punch. The electrostatic discharge can contain 100 million to 1 billion volts of electricity. The energy can heat the air around it to 50,000°F for a short time. Lightning can not only be destructive; it can be deadly. Each year lightning causes over $900 M in property damage and over 80 injuries and 20 deaths, according to the Insurance Information Institute (iii). Also, lightning can strike the same place twice.
The intense energy from a bolt of lightning can start a fire if it strikes combustible materials in your home or chimney. In 2013, the National Fire Protection Agency (NFPA) reported that nearly one out of five lightning fires occurred in homes. The most significant fire risk is the creosote build-up in the chimney. When it hardens into a dark, tarry, and crusty material, it is very flammable. The heat from a lightning strike can spark a fire in the chimney that can also spread to other parts of the home. Therefore, it’s essential to clean your chimney after every winter season.
A lightning strike can also damage the masonry along with the accompanying pouring rain that also occurs. Depending on precisely where the bolt hits, it can damage the chimney cap, cause cracks in the chimney crown, flue liner, and exterior masonry. Small cracks in the masonry are still enough to allow water to get inside the chimney, causing even more damage than the lightning strike itself. Also, if the chimney was already in need of repair, thunderstorms and lightning could further exacerbate the damage.
It is vital to inspect your chimney for lightening damage after the storm passes. One of the clues that may indicate lightning damage is the masonry on the ground beneath the stack. There may also be cracks in the chimney crown that were caused by lightning. Since lightning and storm damage to chimneys may be covered in your homeowner’s insurance policy, you should have a professional chimney technician inspect it after a significant weather event.
A chimney inspector will determine whether the chimney damage was due to lightning or other event and the estimated costs of repair. In the meantime, you will want to make the necessary chimney repairs to prevent the damage from worsening.