Accessory Structures in Anchorage, AK

If you live in Anchorage or are thinking about moving there, accessory structures are one of those things you probably won't think about until they affect you directly. Anchorage has 4 specific rules on the books covering different aspects of accessory structures, and some of them might surprise you.

Shed & Carport Rules

Anchorage lets a private carport encroach into a required side or rear setback next to an alley, but its combined floor area with any garage cannot exceed the house's own square footage in most residential zones.

Key details: Citation: AMC 21.05.070D.10. Setback exception: Alley-adjacent side/rear setback only. Size cap, R-1 through R-2D: 100% of house floor area. Size cap, R-2M/R-3/R-4: 50% of house floor area. Exterior materials: Must match principal structure.

Oversized garages or carports that exceed the floor-area cap, or that encroach outside the alley-setback exception, get flagged at permit review and must be resized, relocated, or removed before a building permit issues.

Tiny Homes

Anchorage lets a tiny home serve as an accessory dwelling only if it's fixed on a permanent foundation, per the zoning code's accessory-use rules.

Key details: Governing code: AMC 21.05.070E.4. Tiny home defined as: "relocatable dwelling unit". Foundation required: Yes, permanent, for ADU use. Applies: All zoning districts.

Code enforcement can order removal or require the unit anchored to a permanent foundation before it counts as a lawful accessory dwelling.

ADU Rules

Anchorage caps accessory dwelling units at 1,200 square feet and 25 feet in height, allowed by right in every residential zone.

Key details: Max size: 1,200 sq ft absolute cap. Size formula: 900 sq ft or 40% of home. Max height: 25 ft (30 ft over garage). Units per parcel: One ADU allowed. Permit needed: Building or land use permit.

An unpermitted or oversized ADU is an illegal accessory structure; the building official can require the owner to bring it into conformance within six months of a compliance order, and failure to legalize it triggers civil penalties under AMC 14.60.030.

ADU Rental Restrictions

Anchorage's accessory dwelling unit rules explicitly promote rental income and set no owner-occupancy or minimum-lease requirement: homeowners may rent out an ADU to any tenant once it is permitted under Title 21 zoning standards.

Key details: Owner-occupancy required: No, not required citywide. ADUs allowed per lot: One ADU per parcel. Girdwood text: ADU may be a rental unit. Permit needed: Building or land use permit. Illegal ADU penalty: Civil penalties, AMC 14.60.030.

Building or renting an unpermitted ADU risks code enforcement; unresolved illegal units face civil penalties under AMC 14.60.030 and the ADU permit itself expires if the unit falls out of code compliance.

Anchorage is more permissive than most cities when it comes to adu rental restrictions. That said, there are still limits.

The Bottom Line

Anchorage's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Anchorage is broadly strict or permissive.

This guide is based on Anchorage's current municipal code. Local rules can and do change, so check the individual ordinance pages for the latest details, penalties, and FAQs.