Accessory Dwelling Unit (ADU).
Columbus City Codes § 3333.325
in effect3333.325 - Accessory Dwelling Unit (ADU).
A. Purpose. To allow Accessory Dwelling Units in conjunction with principal dwellings or apartment houses in apartment residential districts subject to the following provisions regarding allowable number, size, height, and location requirements. Short term rental regulations of Chapter 598 apply to any ADU used for that purpose. An ADU may also be subject to a rental registry upon its implementation.
B. General provisions for an ADU.
1. An ADU may be attached or internal to a principal dwelling or apartment house or may be in a detached building, and must include permanent provisions for living, sleeping, eating, cooking, and sanitation, and have a separate and independent means of ingress and egress.
2. The area district requirements provided for in Sections 3333.10 through 3333.14 for all apartment residential districts may be adjusted as follows regardless of the existing number of units in the principal dwelling or apartment house.
a. For a lot developed with a single principal dwelling or apartment house, two ADUs are allowed in addition to the principal dwelling or apartment house.
b. ADUs may be added to any apartment complex or multiple dwelling development subject to a five percent increase in the maximum number of units per the area district requirements.
c. One ADU may be added to an apartment residential lot developed with a nonconforming residential use.
3. An ADU must be clearly accessory and subordinate in scale to the principal dwelling or apartment house.
a. An ADU must not exceed 65 percent of the minimum net floor area of the principal dwelling or apartment house with which it is associated, or 1,000 square feet, whichever is greater, but in no case shall the ADU exceed the size of the principal dwelling or apartment house.
b. An ADU must not exceed the height of the principal dwelling or apartment house or 25 feet. Exception: the internal alteration of a legally existing principal dwelling, apartment building, or accessory building for the purpose of establishing an accessory dwelling unit shall not exceed 25 feet in height or the height of the existing building where the ADU is being established, whichever is greater.
4. An ADU is not subject to area district lot width requirements per Section 3333.09.
5. Lot coverage shall not exceed 65 percent on a lot with one or more ADUs. Lot coverage shall be calculated using Section 3333.15(b) where applicable.
6. A home occupation is allowed in an ADU, subject to Section 3333.34, but the usable area may be increased to 50 percent of the livable area.
7. An ADU must be located on the same parcel or lot as the principal dwelling or apartment house.
8. No additional parking is required for an ADU.
9. ADUs within an apartment complex or a multiple dwelling development are subject to perimeter yard requirements per Section 3333.255.
10. An ADU must comply with a limited overlay development plan per Chapter 3370, except for any limitation on the number of dwelling units or minimum dwelling unit size. The provisions of subsections 1 and 2 above shall apply for the number of permissible ADUs and size requirements.
C. Detached ADUs are subject to the additional provisions:
1. Must be located in the rear yard area of the principal dwelling or apartment house, and must meet the minimum required side yards of the underlying zoning district. Exception: An ADU located above or within a legally established detached garage building may use the same side yards as the garage.
2. Exempt from fronting and rear yard requirements, per Sections 3333.16 and 3333.24, respectively.
3. One detached ADU may occupy up to 45 percent of the total rear yard of the principal dwelling or apartment house. Two separate or adjoining detached ADUs may occupy up to 55 percent of the total rear yard.
D. The Director is authorized to and may promulgate Rules and Regulations to establish a process to review ADU applications and plans.
(Ord. No. 2526-2025, § 1, 11-24-2025)
Source: City of Columbus, City Codes and City Charter (Municode Library, library.municode.com)URL: https://library.municode.com/oh/columbus/codes/code_of_ordinances?nodeId=TIT33ZOCO_CH3333APDI_3333.325ACDWUNADFetched: 10/27/2026