ADU Rules: Honolulu vs Urban Honolulu
How do adu rules rules compare between Honolulu, HI and Urban Honolulu, HI?
Honolulu and Urban Honolulu have similar restriction levels.
Honolulu, HI
Honolulu County
Honolulu allows one accessory dwelling unit on residential lots of 3,500 sq ft or more. Size is capped at 400–800 sq ft depending on lot size. Owner must live on the property and ADUs may only be rented long-term (six-month minimum).
View full Honolulu rules →Urban Honolulu, HI
Honolulu County
Most Urban Honolulu lots sit in apartment or mixed-use zones where ADUs under ROH Sec. 21-5.720 are not permitted; ADUs are generally limited to R-5 through R-20 single-family neighborhoods like Manoa, Kaimuki, and Nuuanu.
View full Urban Honolulu rules →Key Facts Comparison
| Fact | Honolulu | Urban Honolulu |
|---|---|---|
| Minimum lot size | 3,500 sq ft | - |
| Max ADU size (small lot) | 400 sq ft (3,500–4,999 sq ft lot) | - |
| Max ADU size (large lot) | 800 sq ft (5,000+ sq ft lot) | - |
| Minimum rental term | 6 months (180 days) | - |
| Owner occupancy required | Yes — main house or ADU | - |
| Code Section | - | ROH Sec. 21-5.720 |
| Urban Eligible Zones | - | R-5, R-7.5, R-10, R-20 |
| Not Eligible | - | A-1, A-2, BMX, B |
| Minimum Rental Term | - | 30 days |
Highlighted rows indicate differences between cities.
Honolulu FAQ
Can I rent my ADU on Airbnb or use it as a vacation rental?
No. ADUs are expressly prohibited from being used as bed and breakfast homes or transient vacation units. All rentals must be for a minimum of six months under a written lease.
Do I need a permit to build an ADU or convert an existing structure?
Yes. A building permit is required. Structures built without a permit before September 14, 2015 may obtain an after-the-fact permit to be converted to an ADU.
What happens if I no longer live on the property?
The ordinance allows limited hardship exceptions (e.g., military deployment or serious illness). All other absences require the director's confirmation; failing to maintain owner-occupancy is a code violation.
Urban Honolulu FAQ
Can I build an ADU on my Kakaako or Ala Moana condo lot?
No. ADUs are not allowed in A-1, A-2, or BMX mixed-use zones common in Kakaako and Ala Moana. ADUs are limited to residential R-5 through R-20 districts.
Can I build an ADU on my Manoa single-family lot?
Yes, if the lot meets R-5 or R-7.5 minimum size, parking, and setback rules under ROH Sec. 21-5.720 and you obtain a building permit.
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