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Columbus, OH Accessory Structures: ADU Rules (2026)

Some Restrictions

Compiled from the official code textEditor Martyn O'NeillLast verified September 2026

ADU rules in Columbus, OH, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.

Key Facts

ADUs allowed: One per lot, most residential districts
Size cap: 65% of home or 1,000 sq ft
Height cap: Height of home or 25 feet
Parking: No extra off-street parking required
Penalty: First-degree misdemeanor, § 3305.99

ADU Eligibility Quick-Check

An Accessory Dwelling Unit (ADU) is a smaller, independent living unit on the same lot as a single-family home: converted garages, detached cottages, basement or attic conversions, and attached additions all qualify. Most states have streamlined ADU permitting since 2020, but local rules still control size, height, and setback.

Is your lot zoned single-family or multi-family residential?
Does your lot have at least 1,200 sq ft of buildable space?
Is your existing home owner-occupied (in most states this is not required, but some require it for ADU permits)?
Will the ADU stay under your state's size cap (commonly 850-1,200 sq ft for detached)?
Can you provide one off-street parking space (waived in many states within 0.5 mi of transit)?

If you answered 'yes' to most of these, you likely qualify in Ohio under recent ADU streamlining laws. The Columbus, OH rules below cover local size, height, and setback requirements.

Summary

Columbus allows one accessory dwelling unit per residential lot under Zoning Code § 3332.355, letting homeowners add a small attached, internal, or detached second unit without extra parking or a variance.

To allow Accessory Dwelling Units in conjunction with a principal dwelling in residential districts subject to the following provisions regarding allowable number, size, height, and location requirements... One ADU may be added to a lot containing a single-unit dwelling in all residential districts within Chapter 3332, except as specified below for the R-2F and R-4 districts... An ADU must not exceed 65 percent of the minimum net floor area of the principal dwelling with which it is associated, or 1,000 square feet, whichever is greater.

View official code

Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 85 | Form Based Code: ?).

Full Breakdown

Columbus's Title 33 Zoning Code lets homeowners add one accessory dwelling unit (ADU) to a lot with a single-unit dwelling in every residential district, with two ADUs and up to five total units allowed on R-4 lots. An ADU can be attached, built inside the principal home, or freestanding in the rear yard, but it must include full living, sleeping, cooking, and sanitation space with its own entrance. Size is capped at 65 percent of the principal dwelling's floor area or 1,000 square feet, whichever is larger, and height can't exceed the main house or 25 feet. No extra parking is required. This is the Title 33 standard; corridors rezoned under the newer 2024 Zoning Code follow different ADU rules.

Violations & Fines

Building an oversized, over-height, or unpermitted ADU without zoning clearance is a first-degree misdemeanor under § 3305.99; the Building and Zoning Services director can also void the certificate and order work stopped, with each day a separate offense.

Frequently Asked Questions

Can I add an ADU to any home in Columbus?

Yes, in every residential district under Title 33's Chapter 3332, one ADU is allowed per lot with a single-unit home; R-4 lots can add two ADUs up to five total units.

Do I need extra parking for an ADU?

No. Columbus's ADU ordinance, § 3332.355, specifically states no additional parking is required beyond what the principal dwelling already provides.

How big can a Columbus ADU be?

Up to 65 percent of the principal home's floor area or 1,000 square feet, whichever is greater, but never larger than the main house itself.

Sources & Official References

[1]Columbus City Codes § 3332.355 (Municode)

Other rules in Columbus

Noise Ordinances: Construction HoursSome Restrictions Fence Regulations: Height LimitsSome Restrictions Shed & Carport RulesSome Restrictions ADU Rental RestrictionsSignificant Restrictions Noise Ordinances: Aircraft NoiseLight Restrictions Parking Rules: Towing & Impound RightsSome Restrictions Parking Rules: EV ChargingSome Restrictions Fence Regulations: Retaining WallsSome Restrictions

All Columbus rules

How Columbus compares: Easiest Cities to Build an ADU·Compare Columbus to another location·View the Ohio accessory structures overview

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