Lightning protection for thatched roofs

Although lightning protection for thatched roofs is not a legal requirement, insurance companies may and probably will require that buildings with these roof types have lightning and surge protection. This guidance provides advice on the design of new or improved lightning protection for thatched roofs as well ass proper surge protection systems.

If the recommended protective measures are not implemented such as lightning protection for thatched roofs, the effect of a lightning strike can cause some really serious damage. Thatched roof is one of the most popular design choices in South Africa. These roofs are constructed of material such as straw, reed and grass which is more likely to catch alight as a result of a lightning strikes than any other roof type, according to the South African National Standard (SANS). Thatch is particularly prone to ignition because it becomes ‘fluffy’ at the surface and, if moist, methane and other flammable gases can be formed. When a thatch roof is constructed, wire mesh is used to reinforce and secure the bundles of thatch. Should lightning strike, then current flows through the wire mesh and thermal effects (generated heat) may occur, and set the roof alight.

Lightning protection for thatched roofs requires the installation of a free standing mast – Lightning conductor for thatched roofs. The combustible properties of thatch grass in areas where there is high lighting density poses fire hazards. The aim of the lightning mast is that a preferential point of discharge is provided for the lighting to strike. Note that by installing a mast or external lightning protection on any building will not be sufficient to prevent damage to equipment inside the building as the electromagnetic effects and induction will still cause damage to equipment within the building. In fact, if you install external lightning protection, you will actually require lightning current arresters and surge arresters. A lightning strike up to 1km away can cause damage to sensitive electrical and electronic equipment.

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