Olympia, WA Accessory Structures: ADU Impact Fees (2026)

OMC 15.04.040(A) directs the City of Olympia to impose and collect impact fees from any applicant whose development activity requires a building or occupancy permit. It then adds a cap: per RCW 36.70A, for each category of impact fees, the fees imposed on Accessory Dwelling Units cannot exceed 50 percent of those assessed for a single-family residence or principal unit on the same lot. OMC 15.04.040(C)(6) adds that the creation of an accessory dwelling unit is not subject to school impact fees, so the Olympia School District and North Thurston School District fee schedules do not apply to an ADU.

The fee schedules in Chapter 15.16 carry ADU lines of their own. Schedule A, Park Impact Fees (OMC 15.16.010), prints a single row for Single Room Occupancy Units, Studios and Accessory Dwelling Units at $2,991. Schedule D, Transportation Impact Fees (OMC 15.16.040), effective January 1, 2026, prints a row for Senior Housing, Accessory Dwelling Unit and Single-Room Occupancy Unit at $1,491 per dwelling, and a separate $905 per dwelling for the same row under the Downtown and High Density Corridor fees. These schedules carry a Revised 5/26 tag.

Timing and process follow the general rules. The Director assesses impact fees when the complete building permit application is submitted. The Community Planning and Development Department will not issue a building permit until the fees, less permitted exemptions, credits or deductions, are paid, unless payment is deferred until before the final building inspection. A deferral needs a signed Impact Fee Deferral Agreement acceptable to the city attorney, a $50 administrative fee, and the recording fees at the Thurston County Auditor. The Director decides whether an activity is subject to fees, in writing, and that determination is appealable under OMC 18.70.170. An applicant can also elect an independent fee calculation under OMC 15.04.050 for a $500.00 fee plus a $500.00 deposit.