No. Seattle does not require off-street parking for ADUs; it removed that requirement in 2019. Washington's HB 1337 also bars cities from requiring off-street parking for ADUs within half a mile walking distance of a major transit stop and caps it elsewhere.
Can I build over my parking?
Generally yes, but SDCI asks that existing parking be shown on the site plan, and any covenants on your property still apply.
Street parking
Tenants park on the street like everyone else. In restricted parking zones, check how permits are issued.
Sources, as of November 2026: City of Seattle ADU guidance; Washington HB 1337 final bill report. General information, not legal advice.
Updated November 2026