ADU Permitting in Tampa, Hillsborough, and Pinellas
Tampa Bay has four distinct ADU permit regimes operating on top of each other: the City of Tampa, Hillsborough County (unincorporated), the City of St. Petersburg, and unincorporated Pinellas County. The Florida Building Code (2023 Edition, 8th) applies statewide. A property's address determines which jurisdictional rules stack on top of the state code.
Most ADU permitting mistakes in Tampa Bay trace back to homeowners or builders working from the wrong jurisdiction's rules, or assuming one city's rules apply to neighboring unincorporated land. The City of Tampa does not govern unincorporated Hillsborough County. The City of St. Petersburg does not govern unincorporated Pinellas County.
Hillsborough County (Unincorporated)
Where ADUs are permitted: Most residential districts in unincorporated Hillsborough County. Section 6.11.02 of the Land Development Code defines the standards.
Size: ADU floor area is capped at a percentage of the primary dwelling's gross floor area. The percentage varies by base zone (typical cap is 50%, some zones allow up to 75% for smaller primary dwellings). A small primary home (1,400 sq ft) caps the ADU at roughly 700 sq ft regardless.
Permit path: Standard building permit review with land-development code compliance verification. Typical turnaround 6–10 weeks for first round. Common flags: failure to document the percentage-of-primary-dwelling calculation, missing site plan, incomplete accessory structure checklist.
Hillsborough County is actively updating its ADU ordinance in 2025–2026 to align with expected state law changes under SB 48 and HB 313.
City of St. Petersburg
Where ADUs are permitted: NS-1, NT-1, NT-2, NT-3, NT-4, and NSM zones.
Lot size minimums: NT zones require minimum 4,500 sq ft lot area. NS zones require minimum 10,000 sq ft, unless on an alley or corner.
Size: Maximum 800 sq ft or 67% of the existing primary dwelling, whichever is less.
Design requirements: Architectural compatibility required — the ADU must match the primary dwelling in exterior materials, window style and proportion, roof pitch and material, and door style. These requirements are enforced at permit review.
Rental rules: Minimum rental term is 30 days. Short-term rentals under 30 days are permitted no more than 3 times in any 365-day period.
Permit path: Standard City of St. Petersburg building permit review. Section 16.50.010 of the Code of Ordinances governs. First-round review typically 5–8 weeks.
Unincorporated Pinellas County
Where ADUs are permitted: Most single-family residential zones. Pinellas recently updated its ADU rules to reduce barriers.
Size: 1,000 sq ft maximum in most residential zones. 750 sq ft maximum if the parcel is in the Coastal Storm Area or a flood hazard area (FEMA zones AE, VE, and A).
Parking: ADUs under 750 sq ft are exempt from off-street parking requirements. ADUs over 750 sq ft require one off-street parking space.
Permit path: Standard Pinellas County building permit review. First-round review typically 8–12 weeks (longest in the region). Common delays: flood elevation certification, septic system capacity verification, stormwater retention requirements.
Timeline summary: City of Tampa (overlay) 12–24 weeks total. Hillsborough County 8–18 weeks. City of St. Petersburg 8–14 weeks. Unincorporated Pinellas County 12–20 weeks.
