Leon County, FL Accessory Structures: ADU Rules (2026)

Sec. 803(b) treats accessory dwelling units as a tool for expanding affordable housing, letting a homeowner add a second, subordinate living unit for aging parents, adult children, or rental income without counting it toward the lot's residential density. Only one ADU is allowed per lot or parcel, and it must meet every setback and height standard that already applies to the underlying zoning district. A detached ADU has to go in the side or rear yard, and if the lot is served by an alley, rear-yard placement is mandatory; a front or side-corner location is only available when the principal house itself sits at least 50 feet back from the property line and the ADU keeps a 30-foot setback of its own.

Size is capped by what the ADU serves: 800 square feet of heated and cooled floor area next to a single-family home, or 1,000 square feet gross floor area next to a retail, office, or industrial building. The county also requires the ADU's design, mass, and architectural style to read as clearly subordinate to the primary structure, bars mobile homes, manufactured homes, and storage sheds from ever being converted into an ADU, and requires the unit to be permitted as a full habitable structure. Before a building and environmental management permit issues, the owner must sign and record a notarized affidavit with the Clerk of Courts identifying the structure as an ADU, and it can never be sold off separately unless the parcel is formally subdivided.