ADU rules in Maui

Two detached accessory dwellings are now allowed on essentially any residentially zoned lot in the County of Maui, with no minimum lot size. Ordinance No. 6013 (Bill 78, CD1 (2026)), effective July 8, 2026, rewrote Maui County Code 19.35.050 to read 'No more than two accessory dwellings are permitted per lot, except for rural district lots under chapter 19.29,' deleting the old rule that gave lots under 7,500 sq ft only one unit and gave Molokai and Lanai only one unit at all. Accessory dwellings are a listed permitted use in the residential districts (MCC 19.08.020.G) and, as of Ordinance 6013, also in the R-0 zero lot line residential district, the SBR service business residential district, the zero lot line overlay district and a list of project districts. The county's own July 15, 2026 guide confirms 'Up to two accessory dwellings may be permitted on qualifying residentially zoned lots throughout all of Maui County: Lanai, Maui and Molokai.'

Attached, above-garage and internal or basement units all qualify. MCC 19.04.040 defines an accessory dwelling as 'an attached or detached dwelling unit which is incidental or subordinate to the main or principal dwelling on a lot,' and the county's July 15, 2026 guide illustrates a detached ADU, an ADU over a garage, a basement ADU and an attached ADU. Two design rules bite on attached and internal conversions: MCC 19.35.030 requires at least one separate entrance, and MCC 19.35.040 provides that an accessory dwelling 'shall not have an interior connection to the main dwelling,' so a converted basement or wing must be fully sealed off from the main house and reached from outside. The same two-per-lot cap in 19.35.050 applies whether the units are attached or detached.

Ordinance No. 5966 (Bill 27, CD1 (2026)), effective March 23, 2026, rewrote MCC 19.35.020 and deleted the two smallest tiers, so every lot up to 21,779 sq ft now gets the same 720 sq ft cap instead of 500 sq ft (under 7,500 sq ft) or 600 sq ft (7,500 to 9,999 sq ft). The cap is on 'maximum gross covered floor area,' which includes covered storage and covered walkways or landings up to four feet wide under eaves, and expressly excludes carports, parking spaces and garages plus any laundry or water-heater space inside them. Decks and lanais are capped separately by the same lot tiers under MCC 19.35.060 as amended by the same ordinance: 280 sq ft up to 21,779 sq ft, then 320, 360 and 400 sq ft, counted separately for uncovered and for covered structures. The underlying zoning district's height, setback and lot coverage limits still apply on top of these caps.

Nothing in Maui County Code chapter 19.35 requires the owner to live on the property, and nothing limits occupancy of an accessory dwelling to family members; the chapter sets only building permit, size, entrance, interior-connection, parking, driveway and public-facility standards. Ordinance No. 6013 rewrote 19.35.010, 19.35.050, 19.35.070 and 19.35.090 in July 2026 and added no occupancy test, and Ordinance No. 5966 added none when it rewrote the size sections. Two nearby rules are easy to confuse with an owner-occupancy requirement but are not one: MCC 19.04.040 requires an owner-proprietor to occupy one of the units in a bed and breakfast home, and the Department of Housing's 'Ohana Assistance Program grant (up to $100,000) is limited to owner-occupant full-time residents, but that is a grant condition, not a zoning rule.

Ordinance No. 5983 (Bill 47, CD1 (2026)), effective April 20, 2026, rewrote the parking table at MCC 19.36B.020.E to count bedrooms instead of floor area and folded 'accessory dwelling' into the same row as single-family dwellings, deleting the old flat row 'Dwelling units: accessory dwelling. One for each accessory dwelling.' The table now reads: studio one space, one bedroom one, two bedrooms two, three bedrooms two, four or more bedrooms three plus one for each additional bedroom over four, with an exception dropping that to two plus one per extra bedroom where the fronting roadway is wide enough for two lanes of traffic while vehicles are parked on both sides. MCC 19.35.070, as amended by Ordinance 6013, still requires 'a carport, garage, or other off-street parking space to be used by residents of the accessory dwelling under chapter 19.36B,' and caps the carport or garage at 500 sq ft. A dwelling unit's spaces may be in tandem. Applications filed before April 20, 2026 are processed under the code in effect when they were filed.

Accessory dwellings are a by-right, ministerial use: MCC 19.35.010.B, as rewritten by Ordinance 6013, provides that anyone who wishes to construct or otherwise establish an accessory dwelling 'must apply for a building permit,' and the districts list them among permitted uses rather than special or conditional uses (MCC 19.08.020.G in the residential districts, MCC 19.29.030 in the rural districts, and, new under Ordinance 6013, MCC 19.09.030, 19.11.030, 19.58.030.G, 19.73, 19.74, 19.78, 19.79, 19.80, 19.84.040.B, 19.92.040 and 19.96.100). No planning commission hearing or discretionary permit is required for the dwelling itself. Two administrative gates still apply: MCC 19.35.090 requires written adequacy determinations for sewage disposal, fire protection on lots served by private streets, fire-apparatus street access and, added by Ordinance 6013, adequate water supply; and a parcel inside the Special Management Area needs coastal review under HRS chapter 205A on top of the building permit.

MCC 19.35.010.E, as rewritten by Ordinance 6013, provides that 'Accessory dwellings must not be used as a bed and breakfast home, short-term rental home, or transient vacation rental.' MCC 19.04.040 defines a short-term rental home as accommodations provided for compensation 'for periods of less than one hundred eighty days,' which is why the county's July 15, 2026 guide states flatly that 'an accessory dwelling may not be rented for less than 180 days.' Ordinary long-term renting is unrestricted and is protected by state law: HRS 46-4.8(h) provides that 'No county shall adopt prohibitions on using any dwelling unit on a residentially zoned lot as separately leased long-term rentals, as defined by each county.' There is no family-occupancy or relative-only limit. Owners who take a Department of Housing 'Ohana Assistance Program grant accept a separate deed restriction: at least 10 years of affordable rents and perpetual long-term occupancy.