ADU laws in Alaska

In plain words

Alaska has no state law about ADUs. An ADU (accessory dwelling unit) is a second, smaller home on the same lot as a house. State law hands zoning to boroughs and to many cities. Zoning means the local rules about what can be built where. Boroughs are Alaska's version of counties. Some places have detailed rules, and some have almost none. So whether you can add an ADU depends on your local government. Anchorage is the biggest example. Since 2023 its code allows an ADU with a house or a duplex, if the lot meets its other rules. It can be up to 900 square feet or 40% of the main building, whichever is larger. Anchorage also dropped its owner-occupancy rule. That rule had required the owner to live in one of the two units. It dropped the parking requirement for ADUs too. In 2026 Anchorage began offering free ADU plans that are already approved, though you still need a building permit. Juneau allows detached ADUs up to 1,000 square feet and has offered grants of up to $13,500. A search of the Legislature's records found no bill or law that uses the term 'accessory dwelling unit.' In places with little or no zoning, you still have to meet well, septic and any local building rules. Before you design anything, call your borough or city planning office. Ask what zone your lot is in and what the ADU rules are. You still need permits, and your lot must work for an ADU.

The rules at a glance

What to do next

1. Find out which local government covers your lot: a city, a borough, both, or neither (the unorganized borough).
2. Call that planning office and ask what zone you are in and what its ADU rules say about size, parking and owner occupancy.
3. In Anchorage, look at the free pre-approved ADU plans to save on design costs; you still need a building permit.
4. In Juneau, ask whether the ADU Grant program is open before you apply, since grant applications go in with the building permit.
5. Sort out water, sewer or well and septic approvals early, including any separate water meter your utility requires.
6. If you will finance through an AHFC-backed loan, ask your lender about AHFC's ADU requirements.

What your town still decides

Alaska leaves land use, including ADUs, to local governments. First and second class boroughs and home rule boroughs must provide planning, platting and land use regulation (AS 29.35.180, AS 29.40.010), and a borough may hand those powers to a city that agrees. Home rule and first class cities outside a borough must do the same, while second class cities outside a borough may choose to (AS 29.35.260(c)). Areas outside any organized borough and outside such cities may have no local zoning at all, so building, well and septic rules matter most there. A full-text search of the Legislature's records for 1993-2026 found no bill or statute using the phrase 'accessory dwelling unit'; the term appears only in two committee meetings (2022 and 2023), and in a February 2025 Senate Finance presentation by the Alaska Municipal League that listed ADUs as a local housing tool. A related 2026 law, HB 13 (Chapter 25, SLA 2026, law without the governor's signature, effective September 20, 2026), lets municipalities choose to exempt from property tax a unit converted from short-term to long-term rental, or property rented to a low-income family at no more than 30% of its income (it also adds optional exemptions for first-time homebuyers, some mobile home parks and volunteer emergency responders); it is not ADU-specific but could apply to a rented ADU if the local government adopts it. The state housing finance agency, AHFC, clarified its lender requirements for properties with ADUs in 2025 (Seller-Servicer Memo 25-05).

Examples of local rules

• Municipality of Anchorage: AO 2022-107, passed January 10, 2023, removed the owner-occupancy requirement, allowed an ADU with a single-family home or a duplex, set the size cap at 900 sq ft or 40% of the main building (whichever is larger), and dropped the parking requirement. A 2024 ordinance (AO 2023-87(S-1)) made two-family homes a permitted use in every residential zone. In April 2026 the city began offering free pre-approved ADU plans; building permits are still required. Source
• City and Borough of Juneau: Detached ADUs can be up to 1,000 sq ft; attached or internal ADUs up to 1,000 sq ft or 40% of the main home, whichever is greater. Zoning approval runs through the building permit, a separate water meter is required, and fire and sound separation is needed between units. The city's ADU Grant program has offered up to $13,500 per ADU, with applications taken alongside the building permit; current funding was not confirmed. Source

What we’re still confirming

• Juneau has offered ADU grants, but whether the program is funded and taking applications now isn't confirmed; ask the city.

This is general information, not legal advice. Your town, village, city or county decides what can be built on your property. If something here looks out of date, email the team.