In general there is no rule to route a grounding electrode conductor to the outside you could as addressed in the article run one through an attic space or under a building though the article says it would be common sence to route it outside it is required to be routed outside when the service equipment is inside of a manufactured building
230.6 Conductors Considered Outside the Building.
Conductors shall be considered outside of a building or other structure under any of the following conditions:
(1) Where installed under not less than 50 mm (2 in.) of concrete beneath a building or other structure
(2) Where installed within a building or other structure in a raceway that is encased in concrete or brick not less than 50 mm (2 in.) thick
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