Auburn, AL Accessory Structures: ADU Rules (2026)

02(D)(4) governs accessory dwelling units citywide, whether the unit sits inside an owner-occupied single-family home or in a separate structure on the same lot. The unit must be self-contained, with "its own sleeping room, kitchen, and bathing and toilet facilities" adequate to support independent living. Size is capped hard: the ADU cannot exceed "thirty (30) percent of the floor space in the principal residence or 1,000 square feet, whichever is the lowest," so a large house does not automatically buy a larger accessory unit. Height is limited to two stories, and if the unit sits above a garage, the garage itself counts as the first floor of that two-story structure.

Only one accessory dwelling unit is allowed per lot of record, no matter how large the parcel. The unit must also meet every setback, impervious surface ratio, floor area ratio and other dimensional standard that applies to the principal dwelling's zoning district, and all of its utilities have to run through the principal dwelling rather than getting a separate service connection. The ordinance closes off any workaround: "No accessory dwelling unit shall be approved unless all the conditions set forth above are met. " That no-variance clause makes the size, height, and one-per-lot limits absolute rather than negotiable through the Board of Zoning Adjustment.