Maui County, HI Accessory Structures: ADU Rules (2026)

Maui County's ohana program is codified at Maui County Code Title 19 (Zoning), Chapter 19.35 (Accessory Dwellings) and is administered by the County of Maui Department of Planning. The chapter defines an 'accessory dwelling' as a second or third dwelling unit on a single residential lot that is subordinate to the principal dwelling. Accessory dwellings are permitted only in zoning districts that list them as a permitted or accessory use - principally the R-1, R-2, and R-3 Residential districts and the Rural districts under Chapter 19.29 (Rural districts allow accessory dwellings under both Chapter 19.35 and Hawaii Revised Statutes Chapter 205). The chapter does not allow accessory dwellings in the County's State Agricultural districts under the same framework; agricultural lots use a different farm-dwelling regime under HRS 205. Density caps depend on lot size: lots smaller than 7,500 square feet may have one accessory dwelling, while lots of 7,500 square feet or more may have up to two accessory dwellings (subject to a scheduled state-mandated change). The maximum gross covered floor area of each accessory dwelling scales with net lot area and is set out in the Chapter 19.35 standards table, with thresholds at 7,500, 10,000, 21,780, 43,560, and 87,120 square feet, and a maximum unit size of 1,200 square feet on the largest lots. Accessory dwellings may be detached, attached, or stacked atop one another but must function as independent dwelling units. Each unit must have its own off-street parking, and the project must satisfy the underlying district's setback rules (typically 15 feet front and 6 feet side and rear for buildings of 15 feet or less in height, and 10 feet side and rear for buildings taller than 15 feet under Chapter 19.08). Building permit applications must demonstrate adequate water service - Maui County's Department of Water Supply limits the fixture units served by a standard 5/8-inch water meter, so adding a second or third dwelling commonly requires purchasing additional fixture units or upgrading the meter. Wastewater service must be provided through county sewer where available or an approved individual wastewater system. Use of any accessory dwelling as a short-term rental home, transient vacation rental, or bed-and-breakfast home is expressly prohibited under Chapter 19.35, and Chapter 19.65 (Bed and Breakfast Homes) and Chapter 19.64 (Short-Term Rental Homes) reinforce that prohibition. Hawaii law also shapes Maui's regime in two significant ways. HRS Section 46-4 long authorized counties to permit two single-family dwelling units on a lot where a residential dwelling is permitted, which is the statutory backbone of the ohana program. More recently, Act 39, Session Laws of Hawaii 2024 (originating as SB 3202), enacted HRS Section 46-4.8 and requires every Hawaii county to adopt or amend ordinances by December 31, 2026 allowing at least two accessory dwelling units in addition to the primary dwelling on each residentially zoned lot in an urban (residential) district, regardless of lot size, subject only to limited exceptions where utility infrastructure is insufficient. The statute also bars private covenants from limiting accessory dwellings below that statutory minimum. The Maui County Council referred a proposed implementing bill to the Housing and Land Use Committee on September 3, 2024 to develop the specific Chapter 19.35 amendments. Until that ordinance is adopted, the existing 7,500-square-foot threshold and unit-size schedule continue to control.