Auburn's Accessory Structures: The Rules That Matter
Every city handles accessory structures a little differently. In Auburn, Washington, there are 5 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.
Tiny Homes
Auburn allows tiny homes on foundations as dwellings or ADUs if they meet WA Building Code IRC Appendix Q. Tiny homes on wheels are RVs and cannot be permanent dwellings except in approved RV parks.
Key details: On Foundation: Allowed as house or ADU. On Wheels: RV parks only. IRC Appendix Q: Under 400 sq ft. Code: ACC 15.36 and 18.31.120. State Framework: RCW 43.22 factory-built.
Contact your local code enforcement office for specific penalty information.
Carport Rules
Carports in Auburn follow ACC 15.36 and 18.31. Open carports under 200 sq ft may be permit-exempt but must meet setbacks. Attached carports always require a building permit regardless of size.
Key details: Exempt Size: 200 sq ft or less. Open Sides: 2 sides minimum. Attached: Permit always. Impervious Count: Yes. Wind Rating: 90 mph design.
Contact your local code enforcement office for specific penalty information.
If you are coming from a city with tighter rules, you will find Auburn gives residents more flexibility on carport rules.
ADU Rules
Auburn permits ADUs and DADUs under ACC 18.31.120 per WA HB 1337. Up to two ADUs per lot, max 1,000 sq ft, no owner-occupancy rule. Unit lot subdivision for fee-simple sale is allowed.
Key details: State Law: WA HB 1337 (2024). Units Per Lot: Up to 2 ADUs. Max Size: 1,000 sq ft. Owner Occupancy: Not required. Parking: Waived near transit.
Contact your local code enforcement office for specific penalty information.
The rules around adu rules in Auburn lean permissive, but that does not mean anything goes.
Shed Rules
Auburn follows the 2021 IRC through ACC 15.36. Sheds 200 sq ft or less and 10 ft or less tall do not need a building permit but must meet ACC 18.31 setbacks: 5 ft rear-side, 10-15 ft front. Larger sheds require permits.
Key details: Permit-Exempt Size: 200 sq ft or less. Height Exempt: 10 ft or less. Rear-Side Setback: 5 ft typical. Front Setback: 10 to 20 ft by zone. Rear Yard Cover: Max 50 percent.
Contact your local code enforcement office for specific penalty information.
If you are coming from a city with tighter rules, you will find Auburn gives residents more flexibility on shed rules.
Garage Conversions
Converting a garage to living space in Auburn requires a building permit under ACC 15.36. Independent units become ADUs. Replacement parking not required under WA HB 1337 near transit.
Key details: Permit: Building permit required. Parking Near Transit: Not required HB 1337. Parking Elsewhere: 1 space typical. Egress Window: Required bedrooms. Classified as ADU: If self-contained.
Contact your local code enforcement office for specific penalty information.
The Bottom Line
Compared to many U.S. cities, Auburn gives residents more room on accessory structures. 3 of the 5 rules here are rated permissive. But permissive does not mean unregulated. There are still requirements, and the city does enforce them when violations are reported.
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.