The phrase “lightning never strikes twice” is not correct. The fact is that lightning can strike the same structure time and time again. The Eiffel Tower for instance was struck ten times during one lightning storm.

To fully protect a building from a direct or indirect lightning strike a Risk Assessment needs to be carried out. Once the need for Lightning Protection is established a system needs to be designed specific to the structure under review.

A traditional “Faraday Cage” system comprises of copper or aluminium roof and down conductors and earth terminations i.e. of earth electrodes deep driven in to the ground.

Metallic elements of the structure such as metal clad roofs, parapet capping, structural steelwork, structural reinforcing, pile caps etc can also be used if they comply with the criteria laid down in BS EN 62305:2006.

Surface fixed conductors should be pvc sheathed colour coded to match the fabric of the building. Brown, black, grey, stone, white and green being the colours most readily available.

Individual earth termination must attain a specific resistance to earth. The requisite resistance is dependent on the number of earth terminations in the system and is calculated thus: 10 x the number of earth terminations in the system. For example a system with 5 no. earth terminations; the maximum resistance should not exceed 50 ohms. A system with 15 no. earth terminations; the maximum resistance should not exceed 150 ohms.

The overall resistance of the system should not exceed 10 ohms.

It is essential that Lightning Protection Systems be designed, installed and maintained by trained and competent engineers. All Nimbus Lightning Protection operatives are CSCS card holders endorsed “Lightning Conductor Engineer”. Nimbus are also active members of ATLAS (Association of Technical Lightning and Access Specialists) and SLPTG (Steeplejack & Lightning Protection Training Group).

Nimbus Lightning Protection Ltd. is part of PTSG, a UK market leader that specialises in access and safety, electrical services, specialist building access and fire solutions.

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