Is a DADU different from a regular ADU?
✓ Verified against code · August 19, 2026
No — a DADU (detached accessory dwelling unit) is one kind of ADU, distinguished only by standing apart from the main house rather than being attached to it or built inside it. Washington's HB 1337 regulates all ADUs together, but every one of the 16 city codes in this ledger uses the DADU abbreviation and writes separate height and setback rules for detached units. So the distinction matters a great deal for design even though state law does not treat it as a separate category.
Citation: varies by city — see city pages
How current is this?
Washington’s ADU rules run under HB 1337 (2023). HB 1337 required every Washington city over 25,000 people to allow two ADUs per residential lot, drop owner-occupancy requirements, cap size limits no lower than 1,000 sq ft, cap height limits no lower than 24 ft, and stop requiring parking near major transit — with compliance due June 30, 2025 for larger cities. We verified this answer against primary sources on August 19, 2026, and every change we catch is logged in the changelog.
More Washington ADU questions
- How many ADUs can I build in Washington?
- What is HB 1337?
- Do I need parking for an ADU in Washington?
- Can cities require me to live on the property?
- How big can an ADU be in Washington?
- Can I sell an ADU separately in Washington?
- Which WA cities have pre-approved ADU plans?
- When did WA ADU rules change?
- How tall can an ADU be in Washington?
- How close to my property line can an ADU be built?
- Will I have to pay impact fees on an ADU in Washington?
- How long does it take to get an ADU permit in Washington?
- Do granny flat or mother-in-law mean anything legally?
Not legal advice — local ordinances can go further than the state floor. The citation above points at the governing statute; check your city’s code for the specifics.