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Figure 5.1.5.3 Thatched roof Figure 5.1.5.4 Historical farmhouse with external lightning protection system;
source: Hans Thormählen GmbH & Co.KG.

If a thatched roof is situated next to metal roofing material and requirements for buildings with thatched roof (IEC 62305-3
if the building has to be equipped with an external lightning (EN 62305-3)).
protection system, a non-conductive roofing material with a The ridge of the object is made of heather and is protected by
width of at least 1 m, e.g. made of plastic, must be inserted a plastic meshed network to prevent birds from taking away
between the thatched roof and the rest of the roof. the heather.
When planning the air-termination system, the rolling sphere
Tree branches must be kept at least 2 m away from a thatched method must be used to determine the protected volumes. Ac-
roof. If trees are very close to, and higher
than, a building, an air-termination conduc-
tor must be mounted on the edge of the
roof facing the trees (edge of the eaves, ga- 1 m
ble) and connected to the lightning protec- GRP/Al supporting tube Ø 50 mm
tion system. The necessary distances must
be maintained. 1.5 m rolling sphere with r = 45 m
Another possibility to protect thatched
buildings from lightning strikes is to install
air-termination masts which ensure that
the entire building is located in the pro-
tected volume.
This is described in chapter 5.1.8 “Isolated
air-termination systems” (telescopic light-
ning protection masts).
10 m Legend:
A new and architecturally appealing pos- Down conductor
sibility to install an isolated lightning pro- HVI Conductor
tection system is to use insulated down (underneath
conductors. 2 m the roof)
Figure 5.1.5.4 shows insulated down con- Earth conductor
ductors installed on a historical farmhouse. Test joint
Thatched roof
A lightning protection system according 13 m
to class of LPS III was installed on the his-
torical farmhouse. This meets the normative Figure 5.1.5.5 Sectional view of the main building

80 LIGHTNING PROTECTION GUIDE www.dehn-international.com