A lightning protection system doesn't stop lightning. It gives a strike that would hit your building anyway a safe, planned path into the ground, so the current doesn't find its own way through your roof, walls, wiring and equipment.
The five parts
- Air terminals: rods or a conductor mesh on the roof that intercept the strike.
- Down conductors: copper tape, typically 25 × 3 mm, that carries the current down the outside of the building.
- Earth termination: earth rods and pits that spread the current safely into the ground.
- Bonding: connections that tie roof plant, metal pipes and structures into the system so current doesn't jump between them.
- Surge protection: devices in your distribution boards that stop the surge reaching equipment through cables.
Leave out any one of these and the system can fail. A roof rod with a poor earth, for example, can push dangerous voltages into the building instead of away from it.
Does my building need one?
The international standard, IEC 62305, answers this with a risk assessment. It weighs up:
- The height and size of the building, and whether it stands taller than its surroundings.
- How often lightning strikes in your area.
- What the building is used for and how many people are inside.
- What is inside it: servers, fuel, medical equipment, stock.
- The cost of losing services, such as a bank branch or a telecom site going offline.
Tall buildings, isolated sites, telecom masts, fuel stations and anywhere with critical electronics usually come out as needing protection.
Installed is not the same as working
Conductors get stolen or damaged, joints corrode and earth resistance rises as the ground dries. A system needs testing at handover and inspection at least once a year to stay effective.
Not sure where your building stands? Try our lightning risk checker, then ask for a site risk assessment to confirm it.