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Zoning Guide

ADU Rules in Anchorage, Alaska

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ADU Rules in Anchorage, Alaska

Anchorage is Alaska's largest city and the administrative center of the Municipality of Anchorage (MOA). ADUs (called "accessory apartments" in the local code) are permitted in residential zones under Title 21 of the Anchorage Municipal Code. Alaska has no statewide ADU preemption law.

Permitted ADU Types

  • Detached Accessory Apartment: A separate structure on the same lot as the primary dwelling
  • Attached Accessory Apartment: An addition to the primary dwelling with a separate entrance
  • Internal Conversion: Converting space within the existing home (basement, attic) to a separate unit

Size Limits

ADU Type Maximum Size
Detached ADU 800 sq ft or 50% of primary dwelling
Attached ADU 800 sq ft or 50% of primary dwelling
Internal Conversion 800 sq ft or 50% of existing heated space

Setbacks

Setbacks in Anchorage vary significantly by zone:

  • R-1 (Single Family): Side 5 ft, Rear 20 ft for detached ADU
  • R-2 (Low Density): Reduced setbacks may apply
  • Always verify setbacks for your specific zone at the Planning Department

Height

  • Detached ADU: Must not exceed height of primary structure in most zones
  • Maximum 25 feet in standard residential zones

Climate Considerations

Anchorage construction must account for:

  • Seismic Zone 4: High seismic risk — foundation and structural requirements are strict
  • Frost depth: Footings must extend below frost line (typically 42–48 inches)
  • Snow load: Roof structures must meet code requirements for snow loads

Parking

One additional off-street parking space is required per accessory apartment in most residential zones.

Permit Process

  1. Check zoning: Verify zone and setback requirements via MOA GIS
  2. Design for climate: Work with architect familiar with Alaska building requirements
  3. Submit plans: Complete architectural and site plans
  4. Planning review: Zoning compliance review
  5. Building permit: Issued by Development Services Department
  6. Inspections: All required phases including seismic-related inspections
  7. Certificate of Occupancy: Required before occupancy

Contact

Municipality of Anchorage Planning Department 4700 Elmore Rd, Anchorage, AK 99519 Phone: (907) 343-7921 Website: muni.org/planning

Disclaimer: Verify current requirements with the MOA Planning Department before starting any project. Alaska's climate and seismic conditions require specific construction expertise.

More about Anchorage Zoning

Building PermitsSetbacks & Height Limits

Sources

  1. Anchorage Municipal Code Title 21 — Land Use Regulations·library.municode.com·Accessed 2026-04-07·Direct link
  2. Municipality of Anchorage Planning Department·muni.org·Accessed 2026-04-07·Direct link

FAQ

Are ADUs allowed in Anchorage?
Yes. Anchorage permits accessory dwelling units in single-family and multi-family residential zones under Title 21 of the Anchorage Municipal Code. ADUs are called 'accessory apartments' in the municipal code.
What is the maximum ADU size in Anchorage?
In Anchorage, accessory apartments are generally limited to 800 square feet or 50% of the primary dwelling's floor area, whichever is less. Some zones allow up to 1,000 square feet.
Does Anchorage require owner occupancy for ADUs?
Anchorage does not currently require owner occupancy for all ADU types. However, specific zone standards may apply. Check current Title 21 requirements with the Planning Department.