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Hawaii Act 39 (SLH 2024) — Statewide ADU Mandate (HI)

Tracked preemption from the Hawaii overlay bundle.

Overview

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Effective
2024-07-02
Sunset
—
Authority
state
Scope
state:HI
Other Hawaii preemptions
Maui County Bill 9 (2024) — Apartment District STR Phase-Out (Minatoya List)Gov. Green Affordable Housing Emergency Proclamation (Continuing Series, 2023-2026)Honolulu Ord. 22-7 — Short-Term Rental 90-Day Floor (City & County of Honolulu)Hawaii Native Hawaiian Traditional & Customary Rights (Hawaii Const. Art. XII §7)Hawaii Coastal Zone Management — Special Management Area (HRS Ch. 205A)Hawaii HRS Chapter 343 — State Environmental Review (HEPA)Hawaii HRS Chapter 205 — State Land Use Districts (LUC Classification)Hawaii Conservation District — DLNR Exclusive Jurisdiction (HAR 13-5)
Primary-source summary
[HRS Chapter 205 — State Land Use Law (capitol.hawaii.gov)](https://www.capitol.hawaii.gov/hrscurrent/Vol04_Ch0201-0257/HRS0205/) [HRS Chapter 205 — Justia mirror](https://law.justia.com/codes/hawaii/title-13/chapter-205/) [HRS Chapter 46 — County General Powers (capitol.hawaii.gov)](https://www.capitol.hawaii.gov/hrscurrent/Vol01_Ch0001-0042F/HRS0046/) [HRS §46-15.2 — ADU mandate](https://www.capitol.hawaii.gov/hrscurrent/Vol01_Ch0001-0042F/HRS0046/HRS_0046-0015_0002.htm) [Act 39 SLH 2024 (HB 1630 CD1) — ADU…

Trigger predicate

When this evaluates true for a parcel, the law's preempted fields take precedence over base zoning.

AND
  • parcel.state_land_use_district == urban
  • parcel.base_zone_category ∈ {res_sf, res_mf, res_th, mu}

Preempted fields

5 fields on the base district schema are rewritten when the trigger fires.

FieldOpValueNote
base_districts[category=res_sf].allowed_usesaddaduAt least one ADU permitted as of right on residential-zoned lots, subject to water/wastewater availability
base_districts[category=res_sf].owner_occupancy_required_aduwaive—Counties may not impose owner-occupancy as a condition of ADU permitting
base_districts[category=res_sf].parking_ratio_aducap_at1.0Counties may require 0 or 1 stall — no additional beyond primary dwelling rule
review_typewaive_discretionary—
base_districts[category=res_sf].min_rental_term_days_aducap_at180Rental for >=180 days permitted; counties may restrict STR of ADUs

Citation

Authority source
Act 39, Session Laws of Hawaii 2024 (HB 1630 HD2 SD2 CD1); codified at HRS §46-15.2 (dossier evidence suggests §46-4.8 may be correct codification — verify)
§ Act 39 SLH 2024 — Statewide ADU mandate
https://www.capitol.hawaii.gov/sessions/session2024/bills/HB1630_CD1_.HTM

Research notes

Hawaii's first statewide ADU mandate. Explicit floor-preemption: counties may go less restrictive but not more. All four counties implementing through 2026 (Honolulu Bill 7, etc.). Backdrop was Gov. Green's 2023 Affordable Housing Emergency Proclamation (since reissued bimonthly through 2026-01-16; HI Supreme Court Sep 2025 upheld proclamation class, struck Build Beyond Barriers cert mechanism). CODIFICATION FLAG: repo record cites §46-15.2 but LRB 2024 Acts PDF, Hawaii County Bill 123, and 2025 HB 516 all reference §46-4.8 — verify before correcting.