In the simplest sense, if your project requires permits, then you probably need an architect. New homes, additions, and renovations all must comply with Florida Building Code, and therefore require permits in the State of Florida.
More importantly, the architect is the master of the vision for your project, and has a direct interest in seeing that the design and aesthetic ideas you want are assembled into a finished space.
Additionally, the architect is the planner who considers all of the limitations of your project, including your available space, your budget, your calendar, and the limits of the law, and works to produce the best result within those limitations that satisfies your requirements.
The architect is also your advocate, who represents your project to the municipality, review boards, and even to your contractor. Having an advocate that represents your interests through the full course of your project is often understated, yet the most important reason to work with an architect.