ADU Rules in Columbus, Ohio

Columbus is the capital of Ohio and its largest city, home to more than 900,000 residents in Franklin County. The city has been one of the fastest-growing metros in the Midwest over the past two decades, driven by Ohio State University, a diversified economy, and major corporate investments — including the announced $20 billion Intel semiconductor fabrication campus in adjacent Licking County. That regional growth pressure has made housing production, including accessory dwelling units (ADUs), an increasingly important policy topic.

Ohio Has No Statewide ADU Law

Unlike California or Oregon, Ohio has not passed statewide legislation requiring municipalities to allow or streamline ADUs. Each Ohio city sets its own rules through local zoning ordinances. In Columbus, ADU regulations appear in the Columbus City Code under the zoning chapter, and the standards can vary by zoning district.

Where ADUs Are Permitted

Columbus allows accessory dwelling units in most single-family (SR) and two-family (RR) residential districts. Both attached ADUs (additions to the primary home or internal conversions) and detached ADUs (separate backyard structures) are generally permitted, provided the lot and structure meet applicable standards. Owner-occupancy of either the primary unit or the ADU may be required — verify the current requirement with Columbus Building & Zoning Services.

Size and Setback Standards

Columbus ADU regulations typically impose the following (confirm current code before applying):

• Maximum size: ADUs are generally limited to 50% of the primary dwelling's habitable floor area or an absolute cap (often 800–1,000 sq ft), whichever is less.
• Setbacks: Detached ADUs must meet rear and side yard setbacks for the applicable zoning district — commonly 5 ft from side and rear property lines for accessory structures.
• Height: Detached ADUs are typically limited to one story or approximately 15–18 ft in height.
• Lot coverage: The combined footprint of all structures must stay within the lot coverage maximum for the district.

Special Considerations

Flood zones: Properties near the Scioto River (running through downtown and the west side) or the Olentangy River (north Columbus) may lie within FEMA Special Flood Hazard Areas. Any development — including an ADU — in a regulated floodplain requires a City of Columbus Floodplain Development Permit in addition to the standard building permit.

Historic districts: Columbus has several Historic District Overlay areas (German Village, Victorian Village, Italian Village, Olde Towne East). ADUs in these overlays require review by the Columbus Historic Resources Commission and must meet design compatibility standards.

Short-term rentals: Columbus regulates short-term rental operations separately from ADU permits. Operating an ADU as a vacation rental may require a separate license.

Permit Process

1. Confirm your zoning district and ADU eligibility using the Columbus Parcel Viewer.
2. Prepare site plan, floor plans, and elevations.
3. Submit for zoning clearance review through Columbus Building & Zoning Services.
4. Apply for a building permit (structural, electrical, plumbing, mechanical as applicable).
5. Schedule required inspections during and after construction.
6. Obtain a Certificate of Occupancy before occupying the ADU.

Contact Information

Columbus Building & Zoning Services 111 N. Front Street, Columbus, OH 43215 Phone: (614) 645-7433 Website: columbus.gov/Services/Building-and-Zoning-Services/

Disclaimer: Zoning codes change. Always verify current ADU regulations directly with Columbus Building & Zoning Services and review the Columbus City Code before designing or permitting an ADU. This page is for informational purposes only and does not constitute legal or zoning advice.