Can I build a detached ADU (backyard cottage) in Bellevue?
✓ Verified against code · August 19, 2026
Yes — since July 2025. Detached ADUs were prohibited in Bellevue until Ordinance 6851 took effect. You can now build up to two ADUs per lot, including detached ones up to 1,200 sq ft and 24 ft tall. Note that the City of Bellevue's own older ADU-reform page still describes DADUs as not allowed — it predates the ordinance.
Citation: LUC 20.20.120 (Ord 6851, June 24, 2025)
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
- How big can a Bellevue ADU be?
- 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.