How big can a Bellevue ADU be?
✓ Verified against code · August 19, 2026
1,200 sq ft, excluding up to 300 sq ft of parking or unheated storage. Several national guides state 1,000 sq ft — that's the state-law floor, not Bellevue's adopted limit.
Citation: LUC 20.20.120.C.3
How current is this?
Bellevue’s ADU rules run under LUC 20.20.120 (Land Use Code) (Ordinance 6851). Detached ADUs were prohibited entirely in Bellevue until Ordinance 6851 (adopted June 24, 2025, effective early July 2025). The 2023 ADU reform (Ord 6746) removed owner-occupancy and registration for attached ADUs only — it did not legalize DADUs, despite what several guides claim. Anything describing Bellevue DADU rules with a pre-July-2025 date is describing a prohibition. We verified this answer against primary sources on August 19, 2026, and every change we catch is logged in the changelog.
More Bellevue ADU questions
- Can I build a detached ADU (backyard cottage) in Bellevue?
- Do I need parking for a Bellevue ADU?
- Do I have to live on the property to rent out an ADU in Bellevue?
- Are Bellevue's pre-approved DADU plans available yet?
- Attached or detached — which is easier under Bellevue zoning?
All Bellevue ADU rules → · Compare Washington cities →
Not legal advice — lot-specific overlays can change the answer for your parcel. The citation above points at the governing code section; check it, or ask the city to confirm.