ADU rules in Cincinnati, OH — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Cincinnati legalized ADUs citywide in single-family residential zones effective October 2, 2023 (CMC §1421-06). Detached ADUs: ≤1,000 sq ft or 50% of main home. Attached ADUs: ≤40% of primary. Max height 25 feet. Owner must occupy primary or ADU.
Cincinnati Zoning Code §1421-06 (eff. October 2, 2023) allows ADUs by right in all single-family residential zones. Detached ADUs: maximum 1,000 sq ft or 50% of the main home's sq ft, whichever is smaller; maximum 25-foot height. Attached ADUs: maximum 40% of primary home square footage. One ADU per lot. Either the primary residence or the ADU must be owner-occupied or designee-occupied. ADUs must be registered with the Zoning Administrator. Both long-term and short-term rental use permitted. Structures under 800 sq ft and 13 ft height may not need zoning permits. Building permits required from Dept. of Buildings and Inspections (513-352-3271).
Unpermitted ADU: standard building code enforcement. Zoning violation: cease-and-desist + fines. Must bring to code or remove.
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See how Cincinnati's adu rules rules stack up against other locations.
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