Hawaii Statewide Rule
Hawaii Statewide ADU Authorization Act 39
Key Facts
- Statute
- Act 39 (2024); HRS § 46-4.8
- Compliance deadline
- December 31, 2026
- Minimum ADUs
- Two per residential lot
- Infrastructure
- Adequate water and wastewater
Summary
Act 39 (2024), codified at HRS § 46-4.8, requires every county to amend its zoning to allow at least two accessory dwelling units on residentially zoned lots with adequate water and wastewater infrastructure. Counties must comply by December 31, 2026.
(a) Each county shall adopt or amend accessory dwelling unit ordinances pursuant to this section to help address deficits in their housing inventory based on Hawaii housing planning studies published by the Hawaii housing finance and development corporation.
Full Breakdown
Act 39, Session Laws of Hawaii 2024, enacted HRS § 46-4.8 and directs each county to adopt or amend ordinances allowing at least two ADUs on residentially zoned lots where water and wastewater infrastructure is adequate. Counties must bring their codes into compliance by December 31, 2026. Counties retain authority over design, setbacks, and parking, and may prohibit short-term rental use of ADUs, but may not bar ADUs outright in qualifying residential zones. Implementation varies: Kauai and Hawaii County have already adopted conforming ordinances (Hawaii County allows up to three ADUs), while Honolulu and Maui are still updating their codes.
Violations & Penalties
Counties that fail to adopt conforming ordinances by December 31, 2026 face state review; an owner denied a permit that Act 39 requires may seek judicial review of the denial.
Frequently Asked Questions
Does Act 39 force my county to issue an ADU permit?
Can a county still ban short-term rentals in ADUs?
Sources
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