ADU rules in Pinellas County

The ordinance states the accessory dwelling unit may be attached to the primary unit or be separate/detached. Accessory apartments, garage apartments, and guest houses may be permitted as accessory uses to any single-family detached home in all residential districts. A detached ADU's building height may not exceed the building height of the primary dwelling unit (unless required under Chapter 158) and may not exceed the primary unit's number of stories.

Sec. 138-3210(c)(1)h expressly allows the ADU to be attached to the primary unit. An ADU must have an entrance separate from the primary unit and must contain sleeping quarters, a bathroom, and a full kitchen with sink, cooking unit, and refrigerator.

The 1,000 sq ft cap reflects the July 30, 2024 update (Ord. No. 24-22, the LDR-24-01 amendments), which raised it from 750 sq ft; Ord. No. 26-8 (Feb. 17, 2026) amended the section again without changing the cap. Size can be stretched administratively: Sec. 138-237(b)(1) lets staff adjust building size by up to 20 percent, a power that applies only to accessory dwelling units and accessory residential structures (up to 10 percent at department level, 10 to 20 percent by the County Administrator's designee); the county's announcement says anything beyond 20 percent needs a Board of Adjustment and Appeals variance. The Lealman Form-Based Code and the Downtown Palm Harbor Form-Based Code keep their own rule that 'Accessory dwelling units cannot exceed 750 square feet in area,' with no flood-zone distinction.

Either the primary dwelling unit or the accessory dwelling unit must be owner-occupied. The requirement may be waived if both units qualify as affordable to households at 80 percent or below of median family income (consistent with Chapter 420, Florida Statutes) and are under a Land Use Restrictive Agreement (LURA) for a minimum of 20 years. A signed declaration of land restriction acknowledging the owner occupancy requirement must be recorded with the property deed before the certificate of occupancy is issued. The Lealman and Downtown Palm Harbor form-based codes repeat the owner-occupancy rule ('Either the primary dwelling or the ADU must be owner-occupied') without the affordable-housing waiver.

The ADU section and the county parking table agree: Sec. 138-3210(c)(3) requires the stall only for units over 750 sq ft, and Table 138-3602.a lists Accessory Dwelling Unit at 'None for units 750 sf or less. 1.0 stall per unit if larger than 750 sf.' The parking tables of the Lealman and Downtown Palm Harbor form-based codes (Tables 138-4091.a and 138-4601.b) list the ADU requirement as N/A. An ADU rented as a short-term rental must separately provide one off-street space for every three occupants under the county's short-term rental rules.

Table 138-355 (Table of Uses) lists Accessory Dwelling Unit as 'A' (Accessory Use) in the R-A, R-E, R-R, R-1, R-2, R-3, R-4, R-5, RM and RPD residential districts (and in the CP and MXD columns), not as a Board of Adjustment (Type 2) or BoCC (Type 3) use, subject to the specific use standards of Sec. 138-3210; the RMH mobile home district column is blank. Applicable development review fees are waived for ADUs. In the Lealman and Downtown Palm Harbor form-based code districts an ADU is Type 1A (permitted by right) or Type 1B (permitted by warrant, with Code Administrator approval) depending on the district. An ADU larger than the size cap goes through an administrative adjustment of up to 20 percent (Sec. 138-237) or, beyond that, a variance.

Sec. 138-3210 is silent on lease terms. The county's short-term rental rules (LDC Sec. 138-3232, Ord. No. 25-9 of 3-25-25, and Code Sec. 22-319, Ord. No. 25-15 of 8-5-25, which governs where the two conflict) provide that 'A valid short term rental certificate of use is required for any short term rental unit to be rented or offered for rent in the county.' The certificate lasts one year, requires an inspection before issuance and every two years, and comes with a limit of two persons per bedroom plus two (ten at most), one off-street space per three occupants, quiet hours from 10 p.m. to 9 a.m., and a 24-hour responsible party. The county's STR program page states that 'Owner occupied residences with an accessory dwelling unit such as a guest house or a garage apartment must apply for a Certificate of Use.'