I was asked to add a subpanel in a Tuff Shed that was build beside a new house. The shed is on a concrete slab with fiber reinforcement (no steel rebar...). The main panel for the house is located on the inside wall adjacent to the new shed. Do I still have to drive a ground rod in addition to pulling an ECG from the house or can the ECG be enough since the main panel for the house is so close and grounded to the rebar? Thanks for you guys input!