In the event of the risk assessment stating that Structural Lightning Protection is required, BS:EN 62305-3 assigns a Lightning Protection Class (LPS) to the LPL and deals, in a prescriptive way, with the application of different design principles to create a structural lightning protection system. The designer has a number of material selection criteria and design concepts available, thus enabling him to overcome protection problems, as well as address corrosion, through the selection of appropriate materials.
The key elements decided being . . .
Air Termination system
Using a mesh system, protective angle, rolling sphere method or combination of these.
To avoid sparking or flash-over from the lightning conductor system to conductive metal parts of the building/structure.
Routeing of down conductors
To avoid flash-over – employing physical bonding, the use of Surge Protection Devices (SPDs) or Isolating Spark Gaps (ISGs).
To dissipate the lightning current safely to earth.