Is there a tax break for building an ADU in Olympia?
✓ Verified against code · August 19, 2026
Yes — a 3-year property-tax exemption for ADU construction up to 30% of the original structure's value. The catch: you must file with the Thurston County Assessor before construction begins.
Citation: RCW 84.36.400; city ADU page
How current is this?
Olympia’s ADU rules run under OMC 18.04.060 (Olympia Municipal Code) (Ordinance 7444 (amended by Ord 7457)). Olympia adopted its combined HB 1110/1337 package in November 2025 — about five months after the state deadline — making its rules the freshest of the region's major cities. Its ADU liberalization runs deep, though: zero parking has been the rule here since 2019, and the city's ADU history dates to 1995. We verified this answer against primary sources on August 19, 2026, and every change we catch is logged in the changelog.
More Olympia ADU questions
- Can I sell my Olympia ADU separately from my house?
- Do I need parking for an Olympia ADU?
- How many ADUs can I build, and how big?
- When did Olympia's current rules take effect?
- Does Olympia offer pre-approved DADU stock plans?
- What do Olympia's ADU park impact fees cost?
All Olympia 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.