I always get confused by this but nonetheless heere I go again. house built in 2008. Four wire feed from exterior main service disconnect in the backyard, which was grounded at the meter base ( ground rod). Interior panel was separated and isolated properly, however I did not see a GES (ground rod) at the exterior of the house, which is required, correct, since it’s a detached structure? TIA.
Yes a GES is required for each structure. It could be a CEE (concrete encased electrode) instead of ground rods at the house.
What Robert said. ^^^^^^^^^^