Davidson County operates under a consolidated metropolitan government, meaning the city of Nashville and the county are a single entity. The Metro Department of Codes and Building Safety handles all building permits, zoning, and inspections for the entire county. There are no independent municipal permit departments within the county boundaries.
How this fits with the state
The state authority here is Tennessee Board for Licensing Contractors. The county file does not replace that — it adds the permit office, local overlays, and the actual filing path.