Few renovations do not require a permit. The violence of the natural elements explain this rigorous rules enforce by authorities.
Hurricanes Andrew (1992), Katrina and Wilma (2005) revealed numerous flaws about the strength of the materials used and the quality of construction. Authorities, supported by insurance companies, after these events, decided to strengthen the Building Code and everything goes: structure, standard and low voltage electricity, plumbing, ventilation ... Besides the work must include the upgrade to the residential building code in force.
Before making major renovations, an inspection is required to identify if materials containing asbestos or Chinese Drywall. In the bathrooms and outdoor balconies, a waterproofing membrane must be installed. Same for soundproofing materials under the flooring.
In electricity, a special permit is needed for low voltage devices: alarm system, intercom, close circuit cameras, sound system, central vacuum.
Plumbing, replacement of a single water heater requires a permit. Impact windows and doors require analysis by an engineer and the filing of a plan including the nature of the product selected for a permit.
The severity of the Building Code is primarily a safety issue for you and your neighbors.