Honolulu regulates ADUs in the Land Use Ordinance. California state ADU law does not apply here. Only one ADU is allowed per zoning lot, and ADUs are not permitted on planned development housing or cluster lots.[1]
What is an ADU? An accessory dwelling unit is a small second home on the same lot as the main house: a backyard unit, garage conversion, attached addition or guest house with its own kitchen and bath.
| Size limits | Floor area must not exceed 500 sq ft on lots up to 4,999 sq ft, and 800 sq ft on lots of 5,000 sq ft or more (LUO Article 5 revised text). The ADU must also meet the underlying district development standards for the primary use.[1] |
|---|---|
| Height | Not verified. We did not find this on the official pages we checked. Ask the city before you design. |
| Setbacks | Not verified. We did not find this on the official pages we checked. Ask the city before you design. |
| Parking | Not verified. We did not find this on the official pages we checked. Ask the city before you design. |
| Owner occupancy | The restrictive covenant runs with the land. DPP materials require it to restrict short-term or transient use and set a minimum occupancy period; read the current sample before you file.[3] |
| Permit steps and timeline | Before a building permit, the applicant must get written confirmation that wastewater, water supply and access roadways can handle the ADU, and must record a Declaration of Restrictive Covenants. DPP publishes sample covenant instructions.[1][2][3] |
| Fees | Not verified. We did not find this on the official pages we checked. Ask the city before you design. |
Also worth knowing: An older DPP FAQ page still shows different size numbers (including 400 sq ft on smaller lots). Prefer the LUO text and confirm with DPP before you design.[1]
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Sources
Every fact above links to an official city or state page. Rules change; check the source before you build.
- [1] City and County of Honolulu LUO Article 5 (revised): Accessory Dwelling Unit standards checked Oct 2026
- [2] Honolulu DPP: Building Permit Pre-Application checked Oct 2026
- [3] Honolulu DPP: Restrictive Covenant instructions for ADUs checked Oct 2026