Does a backyard cottage count against Seattle's floor-area limits?
✓ Verified against code · August 19, 2026
Yes — as of January 21, 2026, it does. The interim rule that exempted ADU floor area from FAR was struck by Ordinance 127376. If a guide tells you ADUs are FAR-exempt, it's describing the 2025 interim code, which no longer exists. Model your FAR before assuming you can build two 1,000 sq ft units.
Citation: SMC 23.42.022.J, as amended by Ord 127376
How current is this?
Seattle’s ADU rules run under SMC 23.42.022 and the new Chapter 23.44 (Neighborhood Residential) (Ordinance 127376 (CB 120993)). Seattle rewrote its residential zoning twice in eight months: the HB 1337 compliance package (Ord 127211, May 2025), then the permanent state-compliance code signed December 22, 2025 and effective January 21, 2026, which repealed the old Chapter 23.44 and amended SMC 23.42.022. Most guides written in 2025 describe interim rules that no longer exist. We verified this answer against primary sources on August 19, 2026, and every change we catch is logged in the changelog.
More Seattle ADU questions
- How many ADUs can I build on my Seattle lot?
- Do I need to add parking for an ADU in Seattle?
- Do I have to live on the property?
- Can I sell a Seattle ADU separately from the house?
- What's the fastest way to permit a DADU in Seattle?
All Seattle 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.