BS:EN 62305 recommends the use of a protective mesh of conductors laid over the structure to be protected. This mesh can be supplemented with the use of Air Terminals. The risk assessment carried out from BS:EN 62305-2 determines both the Lightning Protection Level (LPL) and Lightning Protection Class (LPC) for a structure.
Roof mesh spacing
The roof mesh is spaced in accordance with guidelines contained within BS:EN 62305-3. This can be summarised below:
Example of a roof mesh system
Perimeter conductors should be placed close to the edge of the structure. If possible, place down conductors at each corner as well as spacing them equally around the structure.
A minimum of two down conductors is required, whether an Air Terminal, Mesh or Rolling Sphere concept is used.