Auburn's Accessory Structures: The Rules That Matter

Every city handles accessory structures a little differently. In Auburn, Washington, there are 3 distinct rules that residents and property owners should be aware of. Some are stricter than what neighboring cities enforce, and others are more relaxed. Here is what you need to know.

Garage Conversions

Auburn lets homeowners convert garage space into an accessory dwelling unit, but ACC 18.32.010(E)(3) requires the garage door be swapped out for materials matching the house's exterior, and the converted square footage cannot count toward the ADU's minimum size.

Key details: Governing section: ACC 18.32.010(E)(3). Exterior rule: Garage door replaced to match house exterior. Size floor/cap: ADU 300-1,000 sq ft, garage space excluded. Parking: 1 space/ADU unless within 1/2 mile of transit. Permit step: Recorded county statement required before final.

A garage conversion built without matching the garage door replacement to the home's exterior, or one that quietly counts garage floor area toward the ADU's minimum size, is out of compliance with ACC 18.32.010(E)(3) and (D) and can be denied final inspection by the city's building division. Occupying or renting the converted space before the city finals the permit and the recorded title statement is on file with the county risks a stop-work order and permit revocation, since the statement itself warns that future owners must comply with the Auburn Zoning Code for the unit to be lawfully occupied or rented.

ADU Rules

Auburn allows two ADUs per residential lot outright in any residential zone that permits single-unit detached or middle housing, capping each unit between 300 and 1,000 square feet with no more than two bedrooms, attached, detached, or a mix of both.

Key details: Max ADUs per lot: 2 per residential unit. Size range: 300 to 1,000 sq. ft.. Max bedrooms: 2 per ADU. Parking waiver: Within 1/2 mile of transit stop. Utility requirement: Municipal sewer or septic.

Occupying or renting an ADU built or altered without the recorded notice, required permits, or compliant parking is a zoning violation under ACC 18.32.010; removing an ADU without first obtaining city permits and inspections leaves the recorded title notice in place and unreleased.

Shed & Carport Rules

Auburn lets you skip a building permit for a one-story detached tool or storage shed only if its floor area stays at or under 200 square feet. Go bigger, or add plumbing or wiring, and the shed becomes a permitted structure subject to the zone's setback and height table.

Key details: Permit-exempt shed size: 200 sq ft or less, one story. Accessory building height, RC/R-1 zones: 35 feet maximum. Accessory building height, R-2 to R-F: 24 feet maximum. Rear setback, detached structure (R-1): 15 feet. Vehicle-entrance setback: 20 feet from street/alley.

Building a shed over 200 square feet, or one with plumbing or electrical service, without first pulling a permit is a violation of ACC Title 15's adopted building code. Under ACC 15.07.140(E), an unpermitted build is punishable as a misdemeanor (up to 90 days in jail and a $1,000 fine) or as a civil infraction under Chapter 1.25 ACC, at the building official's discretion based on the seriousness of the offense and the owner's compliance effort. The department of community development, per ACC 15.07.140(B), is the enforcing agency and can record a compliance notice against the property with the county recorder if the violation is not resolved.

The Bottom Line

Auburn'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 Auburn is broadly strict or permissive.

These rules come from Auburn's publicly available municipal code. For complete penalty schedules, exemption details, and answers to common questions, see the individual ordinance pages throughout this guide.