Side by side · Ohio
Compare ADU rules across Ohio
Flexible on where you build? The same backyard cottage can be routine in one city and impossible next door. This table puts 3 Ohio cities side by side so you can shortlist the friendly ones before reading a single ordinance, or narrow it to just the cities you are deciding between. Every value is summarized from the city's own code; open a city's page for the full notes, citations, and fine print.
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| City | Detached ADU | Attached / internal | Max size | Owner occupancy | Extra parking | Approval |
|---|---|---|---|---|---|---|
| Cincinnati | Allowed | Allowed | No fixed cap; ADU may not exceed the finished square footage of the principal single-family dwelling. Detached ADU footprint on lots of 4,000 sq ft or more: max 15% of lot area or 800 sq ft, whichever is greater; on lots under 4,000 sq ft, combined footprint of house plus ADU capped at 60% of lot area or 800 sq ft, whichever is greater. Conversions of existing accessory structures are exempt from the coverage caps if the footprint is not expanded. | Required | None. ADUs are exempt from the off-street parking requirements of § 1425-19. | Permitted use |
| Cleveland | Not allowed | Not as an ADU category (none exists), but a second unit inside the house is a permitted principal use in Two-Family Districts: 'Dwelling houses, each occupied by not more than two (2) families' (337.03(a)), with no owner-occupancy or size condition attached. In Limited One-Family and One-Family Districts a dwelling may house only one family (337.02(a)), so an in-house second unit there requires a BZA variance. FBC pilot districts allow 3 to 4 units per site by right. Ordinance read July 2026 | No ADU size standards exist (no ADU use category). Accessory buildings in residence districts may not occupy more than 40% of the required rear yard, and a private garage in a Dwelling House District is capped at 800 sq ft plus 1 sq ft per 12 sq ft of lot area over 4,800 sq ft | Not required | No ADU-specific standard. BZA special permits for 3 to 6 unit conversions in Two-Family Districts require 1 off-street space per family (337.03(c)(5)). In Form-Based Code pilot areas there is no minimum parking at all: 'There are no provisions that establish a minimum number of on-site parking spaces for development' (FBC 4.2.2.B.1) | Citywide: no ADU use exists, so a second unit on a one-family lot needs a use variance from the Board of Zoning Appeals (relief route referenced at FBC 2.2.3.D, Sec. 329.03 Variance). In Two-Family Districts a second in-house unit is by right as a two-family dwelling, and 3 to 6 unit remodels take a BZA special permit (337.03(c)). In FBC pilot districts up to the mapped unit count (3 or 4 per site in H3/H4, more in larger districts) is by right, detached or attached. Cleveland Codified Ordinances 337.02, 337.03, 337.23; Title VIIA Sec. 3002.2, 2.2.3 and Sec. 3001.1, 1.1.7.AFull rules for Cleveland Ordinance read July 2026 |
| Columbus | Allowed | Allowed | 65 percent of the principal dwelling's minimum net floor area or 1,000 sq ft, whichever is greater; never larger than the principal dwelling | Not required | No additional parking required for an ADU | Permitted use |
Summarized from each city's ordinance text, most recently read July 2026. Tap a value marked with an info icon to see exactly what it depends on, straight from the ordinance. Nearly every value has zone, lot-size, or process caveats beyond that; the per-city pages carry the full notes and code citations. Treat this as orientation, not a permit determination.
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Reading the table
- Detached ADU is the make-or-break column for backyard cottages: minimum lot sizes (often 8,000 to 14,500 sq ft) hide behind many of the "Allowed" values, so check your lot before celebrating.
- Attached / internal (basement apartments, additions) is legal almost everywhere and is usually the path of least resistance.
- Approval: "Permitted use" means staff-level sign-off; "Conditional use" means a public hearing, which adds time, cost, and uncertainty.
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