One of the most common questions we receive is: “Doesn’t lightning strike the tallest point? Why can’t I just put one single lightning rod up on my chimney assuming the lightning will hit that?”
Simply because Lightning doesn’t always strike the tallest point. Lightning is actually looking for the path of least resistance. A desirable path to ground. Sometimes there is a more desirable path for the lightning to follow that’s recessed lower than a tall chimney or a cupola. A lightning protection system protects the entire surface area of the home. The rods are placed every 20 feet along the main ridges and on the chimneys. This means that no matter where the lightning hits, it will hit one of the rods and be redirected to the grounding system.
This does not mean that the chimney or antenna that is up on the roof is still not a target. It will certainly be a target for lightning if your building is in a risky location. But it just means that it wouldn’t get hit 100% of the time.
There is only one way to fully protect a building from lightning. Unfortunately you have to do more than putting a rod up at the tall point. We have seen first-hand, houses struck where for a variety of reasons, the lower part of building was the point of the strike. I recall years ago a house in Torrington, CT where lightning actually struck below the roof line because that was where the electrical service fed into the house! We’ve seen countless times where lightning has struck a low, sharp corner of a structure and not the tallest point. There was also a home in Egremont, MA where a tree quite far away from the house was struck. This tree wasn’t any taller than any of the other adjacent trees. It was just luck of the draw. Unfortunately in that particular situation, the lightning traveled down the evergreen tree and arched with a copper gas line. There was a propane tank very close to this tree. This caused the electrical current to start a fire that resulted in a total loss of the house. Fortunately nobody was home when the fire started.
FOR MORE LIGHTNING MYTHS:
http://www.lightningsafety.noaa.gov/myths.shtml