Accessory Structures in Bellevue, WA: What Residents Actually Need to Know

If you live in Bellevue or are thinking about moving there, accessory structures are one of those things you probably won't think about until they affect you directly. Bellevue has 9 specific rules on the books covering different aspects of accessory structures, and some of them might surprise you.

Tiny Homes

Bellevue allows tiny homes on foundations as ADUs under LUC 20.20.120 and WA HB 1337. Tiny houses on wheels are considered RVs and cannot be permanent dwellings. ADU size max is 1,200 sq ft.

Key details: Foundation Tiny Home: Allowed as ADU. Max ADU Size: 1,200 sq ft. Max Height: 24 feet. On-Wheels: Not permanent residence. Code: LUC 20.20.120; IRC App Q.

Occupying a tiny house on wheels as a permanent residence: zoning violation and potential code enforcement. Unpermitted foundation tiny home: stop-work order and correction requirements.

Shed Rules

Bellevue regulates detached sheds under LUC 20.20.125. Structures under 200 sq ft are exempt from building permits but must still meet Land Use Code setbacks. Rear setback is 5 feet.

Key details: Permit Exempt: Under 200 sq ft. Max Coverage: 10% of lot. Rear Setback: 5 feet minimum. Street Setback: 10 feet minimum. Code: LUC 20.20.125.

Sheds built without required setbacks or exceeding coverage: code enforcement citations from Development Services; corrections or removal may be ordered.

Carport Rules

Carports in Bellevue are detached accessory structures under LUC 20.20.125 and require a building permit. Rear setback is 5 feet, and 10 feet from any street right-of-way.

Key details: Permit: Building permit required. Rear Setback: 5 feet (detached). Street Setback: 10 feet. Max Coverage: 10% of lot. Code: LUC 20.20.125.

Building without permit: stop-work order and permit-after-the-fact fees; non-compliant placement requires removal or relocation.

ADU Impact Fees

Bellevue exempts ADUs from transportation and school impact fees in practice, consistent with Washington HB 1337 (RCW 36.70A.696), which caps any ADU impact fee at 50 percent of the single-family rate. Only standard plan-review and building-permit fees apply, plus utility connection charges if a new water or sewer service is needed.

Key details: Transportation Impact Fee: Exempt for ADUs. School Impact Fee: Exempt for ADUs. State Cap: 50% of SFR (RCW 36.70A.696). Building Permit: Per WA fee schedule. Utility Connection: Only if new service.

Failure to pay required permit and connection fees blocks permit issuance and inspection scheduling. Construction without paid permits triggers civil penalties under BCC 1.18 of up to $500 per day, double permit fees on legalization, and possible utility service refusal until charges are paid.

The rules around adu impact fees in Bellevue lean permissive, but that does not mean anything goes.

ADU Permits

Bellevue permits accessory dwelling units under Land Use Code (LUC) 20.20.120, substantially amended by Ordinance 6746 (2023 ADU Reform LUCA). Washington HB 1337 (RCW 36.70A.681) requires Bellevue to allow up to two ADUs per lot in urban growth areas, and the city's middle-housing LUCA is being adopted to comply by the June 30, 2025 statewide deadline.

Key details: Code Section: LUC 20.20.120. Reform Ordinance: No. 6746 (2023). Max Size: 1,200 sq ft or 40% of structure. State Law: HB 1337 / RCW 36.70A.681. ADUs Per Lot: Up to 2 (state-mandated).

Constructing an ADU without permits is a Land Use Code violation under LUC 20.40 (Enforcement) and Bellevue City Code Title 1.18. Civil penalties run up to $500 per day per violation. The city may issue stop-work orders, require removal, and assess double permit fees on retroactive applications. Occupancy without final inspection sign-off is a separate violation.

ADU Rental Restrictions

Bellevue allows long-term rental of ADUs without restriction. Short-term rentals (under 30 days) on ADUs are regulated under Bellevue's Residential Rental Regulations and the city's short-term rental framework. There is no cap on the number of long-term ADU tenants beyond standard occupancy and building-code limits.

Key details: Long-Term Rental: Unrestricted. Short-Term Rental: Requires registration. Rent Control: Preempted (RCW 35.21.830). Landlord-Tenant Law: RCW 59.18. Occupancy Limits: Per IRC / LUC 20.50.

Operating an unregistered short-term rental triggers civil penalties under the Residential Rental Regulations program and back-tax assessments. Long-term rental violations (e.g., habitability, illegal eviction) are enforced under RCW 59.18. Unpermitted ADU rental of a unit that lacks final occupancy sign-off is a separate LUC 20.40 violation with daily fines up to $500.

ADU Owner Occupancy

Bellevue does not require owner-occupancy for ADU properties. The 2023 ADU Reform (Ordinance 6746) explicitly removed the previous owner-occupancy mandate, and Washington HB 1337 (RCW 36.70A.683) prohibits cities from imposing owner-occupancy requirements on ADUs. Owners may rent both the primary dwelling and the ADU to separate tenants.

Key details: Owner-Occupancy Required: No. Removed By: Ord. 6746 (2023). State Preemption: RCW 36.70A.683. Both Units Rentable: Yes. HOA Rules: May still apply privately.

There has been no owner-occupancy violation under Bellevue code since the 2023 reform. Private HOA enforcement is a civil matter handled in King County Superior Court, not by the city. If a city official claims an owner-occupancy violation, point to LUC 20.20.120 as amended by Ordinance 6746 and to RCW 36.70A.683 preempting any such requirement.

If you are coming from a city with tighter rules, you will find Bellevue gives residents more flexibility on adu owner occupancy.

Garage Conversions

Garage-to-ADU conversions are allowed in Bellevue under WA HB 1337 and LUC 20.30; need building permits, must meet habitability codes, and lose required covered parking.

Key details: Authority: Garage conversions allowed as ADU (LUC 20.30). Permit/License: Building permits required. Authority: Must meet habitability code (ceiling, egress). Measurement: HB 1337 waives parking within 0.5 mi transit. Application: Sewer capacity charges apply.

Contact your local code enforcement office for specific penalty information.

ADU Rules

Under WA HB 1337 (2023) Bellevue must allow up to 2 ADUs on single-family lots, max 1000 sq ft each, no owner-occupancy requirement, no additional parking near transit.

Key details: Note: Up to 2 ADUs per single-family lot. Note: Max 1000 sq ft per ADU. Note: No owner-occupancy requirement (HB 1337). Note: No extra parking near transit stops. Permit/License: Building permits via MyBuildingPermit.com.

Contact your local code enforcement office for specific penalty information.

The rules around adu rules in Bellevue lean permissive, but that does not mean anything goes.

The Bottom Line

Compared to many U.S. cities, Bellevue gives residents more room on accessory structures. 3 of the 9 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.

Keep in mind that Bellevue can amend these rules at any council meeting. For the most current version of any rule mentioned here, check the specific ordinance page, where we track updates as they happen.