How tall can a detached Auburn ADU be?
✓ Verified against code · August 20, 2026
24 ft in most residential zones — R-2, R-3, R-4, R-NM and R-F — and 35 ft in the lower-density RC and R-1 zones. A detached ADU counts as an accessory structure, so it takes the accessory-building height from the dimensional table rather than the taller principal-building figure. The 24 ft exactly meets the floor HB 1337 sets; it does not exceed it.
Citation: ACC 18.07.030 Table, row H
How current is this?
Auburn’s ADU rules run under ACC 18.32 (Accessory Dwelling Unit Development Standards) (Ordinance 6959 §1 (Exh. A)). Auburn's ADU chapter dates to Ordinance 6959 in 2024 and has not been amended since — unusual among the cities in this ledger, most of which have amended twice. Auburn spans King and Pierce counties, but applies Title 18 uniformly across both portions; county code does not govern inside city limits. Auburn is also one of the few cities here that sets a minimum ADU size as well as a maximum. We verified this answer against primary sources on August 20, 2026, and every change we catch is logged in the changelog.
More Auburn ADU questions
- How many ADUs can I build in Auburn?
- Is there a minimum ADU size in Auburn?
- Do I need parking for an Auburn ADU?
- Do Auburn's ADU rules differ by county?
All Auburn 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.