ADU laws in Ohio

In plain words

Ohio has no statewide law about accessory dwelling units (ADUs). An ADU is a small second home on the same lot as a house. Examples are a basement apartment, a garage apartment, or a backyard cottage. In Ohio, cities and villages make their own zoning rules. Zoning is the local rulebook for what can be built where. Townships can zone rural land too, but only if their voters approve it. So whether you can add an ADU depends on where you live.

Some big cities now allow them. Columbus voted in November 2025 to allow ADUs by right in all residential districts. By right means the city approves an ADU that meets its standards without a special hearing. You still need a building permit. Cincinnati has allowed ADUs since October 2023. There, the owner or a chosen responsible person must live on the property. This is called an owner-occupancy rule. Many suburbs still ban ADUs or require a hearing.

State lawmakers have not passed any ADU requirement. House Bill 313 would give grants to towns that adopt pro-housing policies, and allowing ADUs is one option. Senate Bill 145 would create an online housing guide that lists towns allowing ADUs. Neither bill would force a town to allow ADUs, and both have sat in committee since 2025. A third bill, House Bill 585, passed the House in June 2026. It would let county disability boards use state housing money to build ADUs, among other homes, but it does not change zoning.

So your local code is what counts. You may be able to build an ADU if local rules and your property allow it. Call your city, village or township zoning office first.

The rules at a glance

What to do next

1. Find out whether your home is inside a city or village or in an unincorporated township; that decides which office sets the zoning.
2. Ask the zoning office whether ADUs (granny flats, carriage houses, in-law suites, accessory apartments) are permitted in your district, need a conditional use hearing or variance, or are not allowed.
3. Get the local limits in writing: owner-occupancy rules (Cincinnati has one), size, height, setbacks, parking and rental limits.
4. Ask the building department and, if you use a well or septic system, the local health department which permits a second unit needs.
5. Check HOA covenants and deed restrictions, which zoning approval does not override.
6. If your town does not allow ADUs, raise it with your council or township trustees; there is no state mandate to lean on, though HB 313 would add grant money for towns that allow them.

What your town still decides

Ohio cities and villages have home-rule power under Article XVIII, Section 3 of the state constitution, and they zone under that power and Revised Code Chapter 713. Townships may zone their unincorporated land under Chapter 519, but township zoning is optional and only takes effect if a majority of township voters approve it, so some rural areas have little or no zoning; counties can also zone unincorporated land under Chapter 303. No Ohio statute requires any of these governments to allow ADUs. A search of the legislature's bill database for 'accessory dwelling' in the 2023-2024 and 2025-2026 sessions finds only grant, toolkit, budget and developmental-disability housing bills; none requires towns to allow ADUs, and none has become law with ADU language. So ADU rules come entirely from local codes. Big cities have moved first: Cincinnati legalized ADUs in 2023 and Columbus made them by right in November 2025. Many suburbs either do not allow ADUs or treat them as conditional uses that need a hearing.

Examples of local rules

• Columbus: Ordinance 2526-2025, passed November 24, 2025, allows internal, attached or detached ADUs by right in all residential and apartment residential districts. ADUs must stay clearly smaller than the main home, and the ordinance waives parking, frontage and lot-width requirements for them. A building permit is still required, and lots in historic or architectural review areas (such as German Village) still need a certificate of appropriateness. Source
• Cincinnati: ADUs have been legal since October 2, 2023 on lots in zones that allow single-family homes and that contain one single-family house; duplexes and apartment lots cannot add one. One ADU per lot, up to 25 ft tall, with no extra parking required. The owner or a designated responsible person must live in the house or the ADU, backed by a recorded covenant, and violations can bring a fine of up to $15,000. Owners register the ADU through the city's ezTrak portal and get building permits. Source
• Cleveland Heights: Ordinance 142-2026, introduced July 6, 2026, would allow one ADU per lot. As revised after public feedback, ADUs would be conditional uses (needing case-by-case approval) rather than by right, with 5 ft setbacks and an 800 sq ft cap on lots under 6,000 sq ft. A public hearing is set for October 15, 2026. Source

What we’re still confirming

• Check Columbus's zoning code (Title 33) for ADU size, height, number-per-lot and owner-occupancy limits; the city's summary leaves them out.

Laws, bills and citations

This is general information, not legal advice. Your town, village, city or county decides what can be built on your property. If something here looks out of date, email the team.