Mountain View, HI

Hawaii County (the Big Island) regulates Accessory Dwelling Units, formerly called 'ohana dwellings,' under Chapter 25 (Zoning) of the Hawaii County Code. After the County Council passed Bill 123 in September 2024 (signed by Mayor Mitch Roth), the County abolished the separate ohana-permit process, redefined ohana units as 'Accessory Dwelling Units' (ADUs), and now allows up to three ADUs per lot in the RS (Single-Family Residential), RD (Duplex Residential), RA (Residential-Agricultural), A (Agricultural), and FA (Family Agricultural) zoning districts. Each ADU is capped at 1,250 sq ft of living area (lanais, garages and carports excluded), must meet the underlying zone's yard setbacks, must have potable water and an approved wastewater system, and is built under a regular building permit (no separate ADU permit required). Bill 123 was adopted to comply with HRS Sec. 46-4.8 (added by Act 39, SLH 2024), the state law that requires every Hawaii county to allow at least two ADUs on residentially-zoned urban lots.

Hawaii County (the Big Island) is one of the largest short-term vacation rental markets in the State of Hawaii, and rentals of an entire dwelling for 30 consecutive days or fewer are tightly regulated under Bill 108 (2018), adopted by the Hawaii County Council on November 14, 2018, signed into law on December 5, 2018 as Ordinance 18-114, and effective April 1, 2019. The ordinance is codified primarily within Hawaii County Code (HCC) Chapter 25 (Zoning) and is administered by the Hawaii County Planning Department under Planning Department Rule 23. New non-owner-occupied short-term vacation rentals (STVRs) are permitted only in: V (Resort-Hotel) zones, CG/CV (General Commercial and Village Commercial) zones, residential and commercial districts within the General Plan Resort Area (resort nodes), and multifamily (RM) zones for units inside condominium properties. STVRs are not permitted in single-family residential (RS, RA) zones or on State Land Use Agricultural lands; the Hawaii Supreme Court unanimously affirmed Bill 108's ag-land prohibition in Rosehill v. County of Hawai'i on September 24, 2024, holding that farm dwellings under HRS Chapter 205 cannot lawfully be operated as transient accommodations. Pre-existing STVRs operating outside permitted zones before April 1, 2019 had until 180 days after the ordinance's effective date to apply for a Nonconforming Use Certificate (NUC); NUCs must be renewed annually with the Planning Department. In addition to a State TAT certificate and General Excise Tax (GET) license, operators must remit a 3% Hawaii County Transient Accommodations Tax (HCTAT) under Bill 81 / Ordinance 21-89 (signed by Mayor Mitchell D. Roth on December 10, 2021), levied on top of state TAT effective January 1, 2022. A new registration regime under Bill 47 (2025) / Ordinance 25-50, signed by Mayor Kimo Alameda on June 25, 2025, will require all hosted and unhosted transient accommodation rentals to register annually with the County; Bill 98 (2025) delayed the Ordinance 25-50 effective date from December 20, 2025 to July 1, 2026 to allow the County time to build the registration system.

Hawaii County (the Big Island) is the only U.S. NFIP community where parcels can simultaneously sit in a FEMA Special Flood Hazard Area, a USGS lava-flow hazard zone, and a Hawaii Emergency Management Agency tsunami evacuation zone. Floodplain development is governed by Hawaii County Code Chapter 27 (Floodplain Management), administered by the Department of Public Works Engineering Division. The county requires a Flood Development Permit for any work in a Special Flood Hazard Area and imposes a 1-foot freeboard above the Base Flood Elevation, exceeding the federal NFIP minimum. Hawaii County is a CRS-participating community providing flood insurance discounts on the roughly 4,400 NFIP policies countywide. USGS Hawaiian Volcano Observatory lava flow hazard Zones 1 and 2 cover much of Puna, Kau, and South Kona, and Zone 1 properties (active rift zones of Kilauea and Mauna Loa) are typically uninsurable for lava and difficult to mortgage.