ADU rules in Florence

Ord. 2025-37 (adopted 9-8-2025) opened detached ADUs for the first time; before it the UDO allowed only integrated (internal or attached) units and barred detached ADUs in every district. Table 1-2.7.2 lists Accessory Dwelling Units as a C (conditional) use in RE, RS, RG, RU, CR and AR and in every Neighborhood Conservation subdistrict (NC-15, NC-10, NC-6.1, NC-6.2, NC-6.3, NC-4), and the UDO defines a C use as permitted by right with administrative approval by the Director. A detached ADU is allowed only accessory to a single-family detached house, must sit in the rear yard at least 10 feet from the house, and counts toward the district's accessory-structure limit.

Integrated ADUs (created within an existing building or attached so they appear part of it) are allowed in the same districts as detached units: RE, RS, RG, RU, CR, AR and all NC subdistricts, as an administratively approved conditional use on a single-family detached lot. The pre-2025 rule (former Sec. 1-2.10.1.B) allowed only integrated units, and not in NC-6.1 through NC-4; Ord. 2025-37 removed that section and extended ADUs to all NC subdistricts. Only one ADU, attached or detached, is allowed per lot.

Sec. 1-2.8.2.A.13 caps a detached ADU at 50 percent of the principal structure's footprint or 1,000 square feet, whichever is less, and an attached ADU at 35 percent of the principal structure's total floor area or 800 square feet, whichever is less. The ADU may be no taller than the principal building (A.15) and may not cover more than 30 percent of the established rear yard (A.14). New-construction ADUs must also meet the district's principal-building setbacks, height, massing and building coverage, and may sit no closer to the side lot lines than the house (A.16).

Either the principal dwelling or the ADU must be occupied by the owner and full-time resident of the property (Sec. 1-2.8.2.A.6). The UDO defines that strictly: the record owner must physically reside there, use the address for voter registration and driver's license, and the parcel must carry the 4 percent owner-occupied (legal residence) assessment ratio in Florence County Assessor records. The requirement is ongoing, not only at application. South Carolina has no state ADU law preempting it.

The current ADU standards in Sec. 1-2.8.2.A contain no off-street parking requirement. Parking Table 4-9.2.2A still sends the Accessory Dwelling Unit row to 'Section 1-2.10.1, Residential Accessory Uses', but Ord. 2025-37 removed the ADU subsection from 1-2.10.1, including its rule of one additional space per ADU bedroom, so the cross-reference now points at text with no ADU parking rule. The main dwelling's standard of 2 spaces per single-family detached dwelling still applies. A.17 bars a separate driveway for the ADU except for a detached unit on a corner lot or alley.

A new ADU, or a change to an existing one, needs a Conditional Use Zoning Certificate before a building permit can be issued (A.4), and an existing ADU needs one before it is rented (A.2). Florence's 'C' conditional use is not a hearing: Sec. 1-2.7.1 defines it as a use 'permitted by right' that 'may be administratively approved by the Director' when it meets the listed standards, so the normal route is staff review. In the city's design overlay districts the ADU also needs a Certificate of Appropriateness from the Design Review Board with public notice (A.5).

An ADU may be rented, but the owner must first get a Conditional Use Zoning Certificate plus a City business license and rental permit (Sec. 1-2.8.2.A.2 and A.3). The rental permit is the annual Residential Rental Registry permit under City Code Chapter 4, Article XIV (Sec. 4-901); Sec. 4-902 exempts individuals owning fewer than five rental units from the business license, but the UDO's ADU rule asks for one regardless. An ADU may not be leased for less than 30 days (A.18), which rules out short-term rental, and it may not be subdivided or held in separate ownership from the house (A.12.b). Short-term rentals in residential districts are otherwise limited to up to two bedrooms inside an owner-occupied primary residence, by BZA special exception.