Grounding electrode requirements are outlined in Sec. 250.52 of the 2011 NEC. A buried iron or steel plate used as a grounding electrode shall expose not less than _____ of surface area to exterior ...

A 2011 Code change to 250.52(A)(7) clarifies that plate electrodes must be conductive. The electrode must be a bare or conductively coated iron or steel plate at least ¼ in. thick, or a solid uncoated ...