Garage conversion rules in Honolulu, HI — sometimes called garage-to-ADU or accessory living unit conversions — govern permits, ceiling height, egress, and parking replacement.
Honolulu's LUO § 21-5.720 allows garage and accessory structure conversions into accessory dwelling units in residential zones, subject to floor area limits, parking requirements, and a building permit from DPP.
Under LUO § 21-5.720, legally established garages and accessory structures in residential (R-3.5 through R-20) and country (AG-1, AG-2) districts may be converted to ADUs. Minimum lot size is 3,500 sq ft. For lots 3,500–4,999 sq ft, the ADU maximum floor area is 400 sq ft. Larger lots allow up to 800 sq ft or more based on zoning. One additional off-street parking space is required per ADU. Parking may be waived if the lot is within 0.5 miles of a rail transit station or if no feasible parking site exists due to topography. A building permit from DPP is required; starting July 1, 2025, certain wastewater impact fees are waived for qualifying ADU projects. Owner-occupancy on the
Unpermitted conversions subject to stop-work orders, fines, and mandatory removal. DPP enforces under ROH Ch. 16 (Building Code) and LUO Ch. 21.
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Side-by-side rule comparisons with other cities in Honolulu County.
See how other cities in Honolulu County handle garage conversions.
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