When Seattle dropped ADU owner-occupancy — and why it changed the math
The 2019 reform that quietly transformed Seattle into one of the most ADU-friendly cities in the United States.
The change
Before 2019, Seattle required that an owner live on the property for at least six months of the year to permit or maintain an ADU. The 2019 ordinance removed that requirement entirely, alongside increased size limits and the second-ADU allowance.
Sightline Institute's coverage at the time correctly predicted the production response.
Sources:Sightline Institute
What it unlocked
Lenders will underwrite an investment property with two rental units on a single lot. They will not underwrite an investment property where the owner is legally required to occupy the property. The repeal made conventional and cash-out refinance financing routinely available for ADU projects on owner-uninhabited lots.
It also legalized the most common practical use case we see: an owner who buys a larger Seattle lot, lives in the primary home for a year while building the DADU, then moves out and rents both units.
What it did not change
ADUs in Seattle still cannot be sold as separate fee-simple units without unit-lot subdivision. Short-term rentals still require a license and primary-residence connection under Seattle FAS rules. And HOA covenants, where they exist, can still restrict ADUs independent of City code.
