Is a building permit required to rebuild an existing deck that is not enlarged?

Yes, if it involves the replacement of joists, beams, railings, or stairs. A permit is not necessary if only the decking (top) is being replaced. All decking should be a minimum of 5/4" nominal lumber thickness. 3/4" inch lumber is not structurally graded or approved for decks. Stair treads must be a minimum of 2X's material.