Accessory Structures in Honolulu County, HI (2026)

5 county-level rules, plus city-specific rules for 11 cities in Honolulu County, Hawaii.

Verified from official government sources

Note: These county rules apply to unincorporated areas of Honolulu County. If you live within an incorporated city, that city's own rules apply — see the city list below.

ADU Rules

Honolulu County allows one ADU per zoning lot in Country, R-3.5, R-5, R-7.5, R-10, and R-20 residential districts, subject to density, parking, occupancy, and rental-duration requirements under the Land Use Ordinance.

Accessory Dwelling Unit Rules Across Oahu

Some Restrictions

Full ordinance details →Official source ↗

Shed Rules

Sheds and similar accessory structures on Oahu must meet yard and street setback requirements in ROH Sec. 21-4.30 and height limits in Sec. 21-4.60, with smaller sheds potentially exempt from building permits under Chapter 18.

Shed Setback and Yard Requirements Islandwide

Few Restrictions

Full ordinance details →Official source ↗

Garage Conversions

Converting a garage into living space on Oahu is typically treated as creating an ADU under ROH Sec. 21-5.720, requiring a building permit under Sec. 18-3.2 and compliance with parking, setback, and occupancy rules.

Garage Conversion Rules on Oahu

Some Restrictions

Full ordinance details →Official source ↗

Carport Rules

Honolulu limits carports and detached garages to maximum horizontal dimensions of 20 by 20 feet under ROH Sec. 21-2.140-1, with hillside Type V-B carports allowed to exceed one story under specified conditions.

Carport Dimensions and Hillside Exceptions

Few Restrictions

Full ordinance details →Official source ↗

Tiny Homes

Honolulu has no dedicated tiny-home ordinance. Permanent tiny homes on foundations are regulated as ADUs under ROH Sec. 21-5.720, while movable tiny homes on wheels are not permitted as permanent dwellings in residential districts.