Is there a checklist of potential damage to look for in a building that has experienced a lightning strike?
We were unable to come up with a checklist of damage that a building might sustain from a lightning strike; however, it is safe to say that any building struck by lightning will sustain some level of damage. How much and what type of damage may or may not be apparent.
Lightning is the discharge of static electricity from the atmosphere to the ground. The way this happens is a leader from the atmosphere pulses toward earth seeking out active electrical grounds. While some ground-based objects emit varying degrees of electric activity causing streamers, when a leader connects with a streamer the connection is complete and the current flows toward earth and through the object that created the streamer. These current levels can exceed 400kA with temperatures up to 50,000 degrees F and speeds approaching one third the speed of light. It is easy see what kind of damage is possible with forces of this magnitude.
According to Dr. Ronald B. Standler’s paper "Consulting on Lightning Damage or Injury," lightning causes damage to buildings in three different ways:
- There can be damage as a result of a direct lightning strike. Such damage may include damage to roofing materials, structures such as chimneys, heating or air conditioning units located on the roof or exterior of a building, or fires caused by lightning igniting combustible material, such as wood-frame buildings or flammable liquids or vapors.
Part of the lightning current can be carried inside a building by electric power, telephone, analog or digital data lines (e.g., closed circuit television cameras, sensors in an industrial plant, etc.). This direct injection of lightning current inside a building can cause immense damage to electrical – and especially electronic – circuits and equipment.
- The electromagnetic fields from the current in a lightning strike can induce currents and voltage in wire and cables inside a building. Such surge currents are typically less intense than direct injection of current, but can easily vaporize integrated circuits in computers, modems, electronic control circuits, etc.
- Lightning can also be conducted along plumbing pipes and other utility piping such as gas lines. Findings from the Orlando Utilities Commission link lightning strikes to pinholes in metal plumbing pipes.
All this points to the fact that lightning damage can be severe, and hidden from a casual inspection. I would suggest a complete inspection of the building’s electrical and plumbing systems by qualified personnel to reduce the future risk of catastrophic failure. While this can be costly if not covered by insurance, this cost would be less expensive than future failures.
This checklist is not intended to be the definitive answer to your question, but rather to provide a starting point and some guidance to you.
Inspect the electrical system
Inspect the plumbing system
- Check breakers to insure they function properly and open the circuit in an over-current situation.
- Check the building's wiring with a resistance tester (megger). This will tell if the high voltage induced by the lightning has damaged the insulation to the point of failure.
- Visually inspect all devices (outlets and light fixtures) for any signs of arcing.
- All telephone, coaxial and other low voltage systems can sustain damage from the effects of lightning, and although not life-threatening, can cause problems with the performance of the systems.
- Pressure test pipes for leaks.
- Visually check for leaks in the pipes and appliances.
For more about potential damage from a lightning strike, see the technical paper
"Recommended Guide for the Protection of Equipment and Personnel from Lightning." There is a section called Isolate Wire-Line Communications, which states,
"The equipment damage from a lightning strike may not be immediate. Sometimes equipment is weakened by stress and primed for failure at some future time. This is called ‘latent damage’ and leads to premature ‘mean time between failure’ (MTBF) of the equipment."
The National Lightning Safety Institute has very detailed information about lightning damage. Click on ‘Structural Lightning Safety’ and then on "5.1.6 Effects of Lightning on Assets, Facilities and Structures." This site has more information on lightning than I found anywhere else.
Lightning Protection Institute