Garage Conversion ADU in Tampa Bay
A two-car garage in Tampa or St. Petersburg averages 400–500 sq ft. On most Pinellas and Hillsborough lots, that garage has already paid for its foundation, its walls, its roof, its electric service, and most of the setback allowances a new ADU would have to earn from scratch. Converting it to a legal ADU costs a fraction of what new detached construction costs, and the permit path is faster.
Garage conversion is not the right answer for every lot. It is the right answer when three conditions are met: the garage is structurally sound, it has room for a code-compliant egress and kitchen, and the homeowner is willing to lose the covered vehicle parking (or relocate it).
Cost comparison at 500 sq ft: Garage conversion runs $60,000–$150,000 in 5–8 months. New detached ADU at 500 sq ft runs $90,000–$160,000 in 9–13 months. New detached at 750 sq ft runs $130,000–$200,000 in 10–14 months.
Step 2: Design and Layout
A converted garage is usually a studio or one-bedroom. Typical 400 sq ft conversion layout: combined living/kitchen/sleeping (260 sq ft), bathroom (45 sq ft), mechanical/storage (35 sq ft), hallway and entry (60 sq ft).
Typical 500 sq ft conversion layout: living/kitchen (220 sq ft), separate bedroom (140 sq ft), bathroom (50 sq ft), closets and circulation (90 sq ft).
We also decide at this stage whether the garage door opening stays, becomes a large window/door combination, or is framed in as a solid wall. Most conversions look best when the garage door opening becomes the primary light source through a large sliding door.
Step 3: Permit Set and Submittal
Garage conversions require permits for four trades: general building, electrical, plumbing, and mechanical (HVAC).
What's in a conversion permit set: Existing conditions floor plan with demo scope. New floor plan and reflected ceiling plan. Wall sections showing new insulation and framing. Electrical plan with new load calculation. Plumbing riser diagram. Mechanical plan showing new mini-split or ducted HVAC. Structural review letter. Egress window specifications.
Review times: City of Tampa 6–10 weeks first round. City of St. Petersburg 5–8 weeks. Unincorporated Pinellas County 8–12 weeks. Hillsborough County 6–10 weeks.
Step 4: Construction
A typical 400–500 sq ft garage conversion runs 10–18 weeks of active construction:
1. Demo (1 week)
2. Site work for plumbing tie-in and slab modifications (1–2 weeks)
3. Rough framing, insulation, and window openings (2 weeks)
4. Rough plumbing, electrical, HVAC (2–3 weeks)
5. Inspections and drywall (2 weeks)
6. Finishes — flooring, cabinets, tile, paint (3–4 weeks)
7. Trim, fixtures, appliances, punch (2 weeks)
8. Final inspection and certificate of occupancy (1–2 weeks)
Weather does not slow a Tampa Bay garage conversion the way it slows new construction. Most critical work happens inside the existing envelope, so the schedule is more predictable.
