East Honolulu, HI Accessory Structures: ADU Rules (2026)

East Honolulu has no separate city government; it is part of the City and County of Honolulu, whose Land Use Ordinance (LUO), Revised Ordinances of Honolulu (ROH) Chapter 21, governs accessory dwelling units (ADUs) island-wide on Oahu. The ADU program was created by Ordinance 15-41 (Bill 20 (2015), CD1), signed September 14, 2015, which added Section 21-5.720 to allow ADUs as a permitted use in the residential (R-3.5, R-5, R-7.5, R-10, R-20) and country zoning districts. An ADU is a second dwelling unit with its own kitchen, bedroom, and bathroom, attached to or detached from the principal dwelling. An ADU is allowed only on a zoning lot of 3,500 square feet or more with a single existing or proposed principal dwelling unit, subject to adequate infrastructure and all other LUO requirements, and only one ADU is allowed per lot. The maximum floor area is 400 square feet on lots from 3,500 to 4,999 square feet, and 800 square feet on lots of 5,000 square feet or more. One additional off-street parking space must be provided for the ADU on top of the parking required for the principal dwelling, except for ADUs within one-half mile of a rail transit station, and the ADU space may be a compact stall. Before a building permit issues, the applicant must obtain written confirmation from the responsible agencies that wastewater treatment and disposal, water supply, and access roadways are adequate. The owner must record a covenant running with the land with the State Bureau of Conveyances or Land Court (or both) on a form approved by the Director; the covenant bars renting the ADU for less than long-term use and bars separating ADU ownership from the principal dwelling under a condominium property regime. The comprehensive LUO rewrite adopted as Ordinance 25-2 (in effect September 30, 2025) raises the small-lot maximum to 500 square feet and carries forward the single-ADU, infrastructure, and covenant requirements.