Maui County, HI Accessory Structures: ADU Rules (2026)
ADU rules in Maui County, HI, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- Smallest lot cap
- 500 sq ft on lots under 7,500 sq ft
- Largest lot cap
- 1,200 sq ft on lots 87,120+ sq ft
- Maui unit count
- 1 unit under 7,500 sq ft; 2 units above
- Molokai/Lanai unit count
- 1 unit, only on 7,500+ sq ft lots
- Required features
- Separate entrance, no interior connection
Summary
Maui County scales an accessory dwelling's maximum floor area to lot size, from 500 square feet on small lots up to 1,200 square feet on lots over two acres, and caps how many can go on one lot depending on the island.
Lot Area (in square feet) Maximum Gross Covered Floor Area (in square feet) Up to 7,499 500 7,500 to 9,999 600 10,000 to 21,779 720 21,780 to 43,559 840 43,560 to 87,119 960 87,120 or more 1,200
... A.Maui:1.No more than one accessory dwelling shall be permitted on any lot that is less than 7,500 square feet.2.No more than two accessory dwellings shall be permitted on any lot that is 7,500 square feet or greater.B.Molokai: One accessory dwelling shall be permitted on a lot that is 7,500 square feet or greater.C.Lāna‘i: One accessory dwelling shall be permitted on a lot that is 7,500 square feet or greater.
Full Breakdown
35 sets the sizing and density rules for accessory dwellings across the county. 020 ties the maximum gross covered floor area directly to the lot's size: a lot up to 7,499 square feet is capped at 500 square feet of covered floor area, rising to 600 square feet on lots from 7,500 to 9,999 square feet, 720 square feet from 10,000 to 21,779 square feet, 840 square feet from 21,780 to 43,559 square feet, 960 square feet from 43,560 to 87,119 square feet, and 1,200 square feet on lots of 87,120 square feet or more.
The section defines covered floor area to include covered storage but exclude carports, parking spaces, and garages, along with narrow covered walkways or landings under eaves. 050 then limits how many accessory dwellings a single lot can carry, and the rule differs by island: on Maui, a lot under 7,500 square feet gets one accessory dwelling and a lot of 7,500 square feet or more can carry two, while on both Molokai and Lanai only one accessory dwelling is allowed per lot, and only once the lot reaches 7,500 square feet. 060 further caps deck, patio, and lanai area on a sliding scale that mirrors the floor-area table.
Violations & Fines
Building an accessory dwelling that exceeds the floor-area cap for its lot size under section 19.35.020, or adding a second unit on a Molokai or Lanai lot where only one is allowed under section 19.35.050, puts the structure outside the building permit that section 19.35.010(A) requires before any accessory dwelling can be constructed. Because the chapter's limits prevail over conflicting district standards under section 19.35.010(B), a plan that exceeds these caps cannot be approved through a general zoning variance.
Frequently Asked Questions
How big can a Maui County accessory dwelling be?
How many accessory dwellings can one lot have on Maui island?
Are the rules different on Molokai and Lanai?
Sources & Official References
Other rules in Maui County
How Maui County compares: Easiest Cities to Build an ADU·Compare Maui County to another location·View the Hawaii accessory structures overview
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