ADU rules in Seminole County

Ord. 2026-12 replaced the Land Development Code's accessory dwelling unit definition with the state statute's wording: an ancillary or secondary living unit with its own kitchen, bathroom and sleeping area, existing either within the same structure or on the same lot as the primary dwelling. Sec. 30.6.1.3 allows ADUs in all single-family, agricultural and rural districts and in single-family Planned Development lots; detached ADUs in A-3, A-5 and A-10 must keep the main house's front setback unless set back at least 100 feet from the front property line. ADUs are permitted by right in A-3, A-5 and A-10 and with administrative approval by the Planning Manager in the R-1 districts, RC-1, A-1 and single-family PD lots. A detached ADU of any size must meet all district setbacks that apply to the main house (Sec. 30.7.3 footnote 1).

The definition now covers a unit 'within the same structure' as the primary dwelling, so an ADU may be part of the house. An existing home may itself become the ADU when a new principal unit is built, as long as the converted structure meets the ADU size limits; Ord. 2026-12 deleted the old rule that the new home be at least 285 percent of the original unit's size and the 1,000 square foot cap on converted structures. Attached ADUs in R-1, RC-1, A-1 and PD lots still need Planning Manager approval and must be architecturally compatible with the principal dwelling.

Ord. 2026-12 moved the size cap out of the definition into Sec. 30.6.1.3(a)(6), raised it from 35 percent of gross floor area or 1,000 square feet to 50 percent of living area or 1,100 square feet, set a 1,600 square foot cap in A-3, A-5, A-10 and on A-1 parcels over three acres, and added a 700 square foot floor 'in all zoning districts that allow accessory dwelling units'. Living area means the space used for living, sleeping, eating, cooking, bathing, washing and sanitation (Sec. 2.3). The same ordinance deleted the ADU row and the 1,100 square foot footnote from the Sec. 5.19 administrative adjustment table, and variances on ADU size or on lot area and width where an ADU is proposed 'are not permitted', so the caps are firm. One ADU per lot or parcel. A separate rule still limits each detached accessory building to 50 percent of the principal building's living area outside A-3, A-5, A-10 and A-1 parcels over three acres (Sec. 30.6.1.2(e)); how that interacts with the 700 square foot floor for a detached ADU beside a house under 1,400 square feet of living area is not addressed in the text.

On any lot containing an ADU, either the principal dwelling or the ADU must be occupied by the property owner, and the ADU may not be subdivided or conveyed into separate ownership from the principal dwelling; Ord. 2026-12 left this sentence unchanged. The Building Division has applicants sign a notarized Owner Statement of Acknowledgment naming which unit the owner will live in.

The ADU space may not be located within a required buffer or setback area. Ord. 2026-12 deleted the former bar on placing the space to the rear of the unit; the county's acknowledgment form (revised 9-10-2025) still prints the old wording.

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 single-family PD lots (minimum 5,000 square feet and 50 feet wide) they are permitted with 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; PD lots follow the approved stormwater design). ADUs are not permitted with nonconforming residential development in Industrial, Commercial, Office or Higher Intensity Planned Development future land use designations.

Ord. 2026-12 added that the 30-day minimum applies 'notwithstanding section 509.032(7)(b), Florida Statutes', the state preemption of local limits on vacation-rental duration (which exempts only rules adopted on or before June 1, 2011); the county asserts the minimum anyway, and this directory has not seen it tested. The county's separate vacation rental registration rules (Sec. 30.6.16) govern rentals of under 30 days and do not mention ADUs. The section adopts the Legislature's view in F.S. 163.31771 encouraging ADUs as affordable rentals, and the ADU may not be sold separately from the principal dwelling.