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Zoning Guide

ADU Rules in Juneau, Alaska

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ADU Rules in Juneau, Alaska

Juneau is Alaska's capital and is uniquely accessible only by air or water. With limited developable land squeezed between mountains and the Gastineau Channel, housing is scarce and ADUs play an important role in the housing stock. The City and Borough of Juneau (CBJ) permits ADUs under Title 49 of its Land Use Code.

Permitted ADU Types

  • Detached ADU: A separate structure on the same lot
  • Attached ADU: An addition to the primary home with separate entrance
  • Conversion ADU: Converting an existing garage, basement, or accessory building

Size Limits

ADU Type Maximum Size
Detached ADU 800 sq ft or 50% of primary dwelling
Attached ADU 50% of primary dwelling floor area
Conversion ADU Existing footprint

Setbacks

  • Front: Must comply with base zone (typically 20–25 ft in residential)
  • Side: 5 feet minimum
  • Rear: 15–20 feet minimum depending on zone

Height

  • Detached ADU: Maximum 25 feet
  • Cannot exceed height of primary dwelling

Terrain and Hazard Considerations

Juneau has significant natural hazard overlays:

  • Avalanche Hazard Areas: Parts of Juneau hillside neighborhoods are in avalanche run zones — development may be restricted or require avalanche mitigation
  • Steep Slopes: Areas over 25% slope require geotechnical analysis
  • Wetlands: CBJ wetlands must be avoided or require permits
  • Landslide Hazard: Some areas have landslide risk — review CBJ hazard maps

Check the CBJ GIS system and Natural Hazards maps before planning.

Climate Considerations

  • Annual precipitation exceeds 60 inches — proper drainage and waterproofing are critical
  • High wind areas may require additional structural design
  • Seismic design required (Alaska is Seismic Zone 4)

Parking

One off-street parking space is required per ADU where physically feasible. In some high-density or transit-served areas, parking requirements may be reduced.

Permit Process

  1. Hazard assessment: Check CBJ hazard maps for avalanche, landslide, wetland areas
  2. Zoning check: Verify eligibility with CBJ Community Development
  3. Geotechnical review: May be required for steep or hazardous sites
  4. Submit plans: Complete architectural and site plans
  5. Planning review: Zoning and hazard compliance review
  6. Building permit: Issued by CBJ Community Development
  7. Inspections: All required phases must pass
  8. Certificate of Occupancy: Required before occupancy

Contact

City and Borough of Juneau Community Development Department 155 S. Seward Street, Juneau, AK 99801 Phone: (907) 586-0715 Website: juneau.org/community-development

Disclaimer: Juneau's unique terrain and natural hazards require careful site analysis. Verify all requirements with CBJ Community Development before starting any project.

More about Juneau Zoning

Sources

  1. City and Borough of Juneau Title 49 — Land Use Code·library.municode.com·Accessed 2026-04-07·Direct link
  2. City and Borough of Juneau Community Development Department·juneau.org·Accessed 2026-04-07·Direct link

FAQ

Are ADUs allowed in Juneau, Alaska?
Yes. Juneau permits accessory dwelling units in residential zones under the City and Borough of Juneau's Land Use Code (Title 49). Given Juneau's unique geography — surrounded by mountains and water with no road connection — housing availability is especially constrained, making ADUs valuable.
What is the maximum ADU size in Juneau?
Accessory dwelling units in Juneau are generally limited to 800 square feet or 50% of the primary dwelling's floor area, whichever is less.
Are there special terrain restrictions for ADUs in Juneau?
Yes. Many areas of Juneau are subject to avalanche hazard, landslide, and steep slope restrictions. Development in these hazard areas requires additional geotechnical review.