Florida ADU Laws 2025: What St. Petersburg Homeowners Need to Know

As Florida's housing market continues to tighten, Accessory Dwelling Units (ADUs)—also known as granny flats, in-law suites, or backyard cottages—offer a practical solution for St. Petersburg homeowners. These secondary living spaces can provide rental income, house extended family, or serve as home offices.

In 2025, while statewide laws encourage ADUs for affordable housing, no new mandates were enacted after Senate Bill 184 died in June. This guide navigates Florida's ADU legislation, Pinellas County requirements, and St. Pete-specific zoning, setbacks, and rules for tiny houses. Whether you're in historic Old Northeast or sunny Shore Acres, understanding these regulations is key to a smooth build.

Florida's Statewide ADU Framework in 2025

Florida Statute 163.31771 defines an ADU as a secondary unit with its own kitchen, bathroom, and sleeping area on the same lot as the primary home. It allows local governments to adopt ordinances permitting ADUs in single-family zones to boost affordable rentals. If your ADU is for low- to moderate-income tenants (rent not exceeding 30% of their income), it counts toward local affordable housing goals, and you'll need an affidavit affirming this during permitting.

No major changes hit in 2025. A bill (S0184) aimed to require all counties and cities to allow ADUs by December 1, without extra parking or owner-occupancy rules, but it failed to pass. However, the state still promotes ADUs through property tax incentives for affordable units.

Pinellas County Requirements and Incentives

St. Petersburg operates under its own municipal code, but Pinellas County rules apply for unincorporated areas and county-wide programs like taxes. In 2024, the county updated ADU regulations to ease building: max size increased to 1,000 sq ft (750 sq ft in flood or coastal storm areas), development fees waived, and owner-occupancy waived for affordable housing units with a 20-year agreement. ADUs need a separate entrance, full kitchen, and bathroom.

Multigenerational Tax Exemption

A key 2025 perk is the multigenerational tax exemption: If you build or renovate an ADU for parents or grandparents (age 62+), you get a reduction on the added property value—up to 20% of the total assessed value post-improvements. Apply via the Pinellas County Property Appraiser; it's available county-wide, including St. Pete. False claims can lead to liens, so document eligibility carefully.

For zoning in unincorporated Pinellas, ADUs are allowed in residential districts with setbacks varying by zone (e.g., side/rear often 5 ft for accessory structures). Parking is exempt for units ≤750 sq ft; larger ones need one space.

St. Petersburg-Specific Zoning and Eligibility

In St. Pete, ADUs are permitted in Neighborhood Traditional (NT) and Neighborhood Suburban (NS) districts, covering about 70% of single-family lots. Use the city's free ADU Map Look-up tool or email DevRev@stpete.org to check your property.

• NT Districts: Minimum lot size 4,500 sq ft.
• NS Districts: 10,000 sq ft, or 4,500 sq ft on an alley or corner lot.

You must be the owner-occupant; the ADU can't be your primary residence. Short-term rentals (<30 days) are limited to three times per year.

Size Limits, Setbacks, and Design Standards

St. Pete caps ADUs at 800 sq ft or 67% of the primary home's floor area (whichever smaller), including all under-roof areas. Detached units exclude up to 300 sq ft per parking space (max three).

Setbacks

• Detached in NS: Side yard min 10 ft (7.5 ft on alley).
• Attached: Follow district setbacks (typically front 18-25 ft, side 5-10 ft, rear 10-22 ft).
• Second-story elements (porches, stairs) facing side yards: Min 10 ft setback.

Height

Detached ADUs can't exceed primary home height; overall, 20-30 ft to roofline depending on district.

Design Requirements

Design must match the main house's architecture (materials, roof, colors). Stormwater management is mandatory—gutters directing water away from neighbors. For garage conversions, remove the door and add landscaping.

Parking and Accessibility

One additional off-street parking space is required, preferably alley-accessed to preserve curb appeal. Exemptions apply if:

• Within 660 ft of high-frequency transit
• ≤600 sq ft in size
• On alley with all parking alley-accessed
• No front driveway

Provide a 2-ft-wide paved walkway to the ADU entrance and space for waste bins.

The Permit Process

Start with eligibility verification, then submit plans via ePlan: architectural drawings, site survey, and energy calculations. Review takes 3-5 business days. Hire a licensed contractor (or self-build under Florida Statute 489).

Total build costs typically range from $160K-$370K for detached ADUs, or $75K-$150K for garage conversions. The process generally takes 3-6 months to Certificate of Occupancy.

Tiny Houses as ADUs in St. Pete

Tiny houses qualify as ADUs if they meet code: full kitchen/bath, size limits, and foundations (no wheels for permanent installs). They're ideal for St. Pete's compact lots but must comply with setbacks and flood rules. Prefab options can cut costs, but permits are still needed.

Conclusion

For St. Petersburg homeowners, 2025 ADU laws build on existing flexibility, with no sweeping state changes but valuable county tax breaks for family housing. Always consult professionals—start with the city's tools and consider HOAs.

An ADU can add value (up to 30%) and income ($1,500-$2,500/month rent), addressing Florida's housing needs while enhancing your property.