ADU rules in Seminole County

The Land Development Code defines an accessory dwelling unit as one that is attached to a principal unit or located on the same lot, and Sec. 30.6.1.3 sets standards for ADUs located in a detached structure (front setback matching the main structure). Allowed in all single family, agricultural, and rural districts and in single-family Planned Developments; by right in A-3, A-5, and A-10, and with administrative approval by the Planning Manager in R-1 districts, RC-1, A-1, and PD.

The definition of accessory dwelling unit expressly covers a unit attached to the principal unit with an independent means of entry. An existing home may itself become the ADU if a new principal unit at least 285 percent of the original unit's size is built; an existing structure converted to an ADU may be no larger than 1,000 square feet except as adjusted under Sec. 5.19(b).

The 35 percent or 1,000 square foot cap sits in the ADU definition itself and is restated for A-3, A-5, and A-10 in Sec. 30.6.1.3(b)(1)b. The Board of Adjustment is barred from considering variances on ADU size or on minimum lot area and width for ADU lots (Sec. 30.6.1.3(a)(6)); the only relief is the Director-level administrative adjustment in Sec. 5.19, capped at 10 percent and an absolute 1,100 square feet. One ADU per lot or parcel. An accessory building also may not exceed the principal building in mass, size, and height (Sec. 30.6.1.2(e)).

On any lot containing an ADU, either the principal dwelling or the ADU must be occupied by the property owner. The ADU may not be subdivided or conveyed into separate ownership from the principal dwelling. The county has applicants sign an owner-occupancy acknowledgment affidavit at permitting.

The ADU parking space may not be located within a required buffer or setback area, or to the rear of the unit.

No public hearing or conditional use process. ADUs are permitted by right in A-3, A-5, and A-10; in all R-1 districts, RC-1, A-1, and in single-family PD lots (minimum 5,000 square feet and 50 feet wide) they are permitted subject to administrative approval by the Planning Manager, including architectural compatibility review with building elevations submitted before permits. Impervious-coverage caps by district apply (30 to 65 percent). ADUs are not permitted with nonconforming residential development in Industrial, Commercial, Office, or HIP future land use designations.

The section expressly adopts the Florida Legislature's view in F.S. 163.31771 encouraging ADUs as affordable rentals. The ADU may not be sold separately from the principal dwelling.