Accessory Structures in Olympia, WA (2026)
5 verified accessory structures rules for Olympia, Washington, sourced directly from the municipal code and official government pages.
Verified from official government sources
ADU Rules
In the City of Olympia, Washington, every residential district allows up to two accessory dwelling units per lot alongside any principal unit. Each ADU is capped at 1,000 square feet of gross floor area, and covered porches are limited to 120 square feet per unit and cannot be enclosed.
Olympia WA Accessory Dwelling Unit (ADU) Rules
Some RestrictionsOlympia Municipal Code § 18.04.060(A)
Accessory dwelling units (ADU) are permitted in all residential districts subject to the following requirements: 1. Number. Up to two ADUs are allowed per residential lot in conjunction with any principal unit. ... 3. Size. ... Each ADU must have a gross floor area of no more than 1,000 square feet. Covered porches or patios (or similar covered spaces) do not count toward the gross floor area o...
ADU Impact Fees
In the City of Olympia, Washington, impact fees on an accessory dwelling unit cannot exceed 50 percent of those assessed for the single-family residence or principal unit on the same lot, and creating an ADU is not subject to school impact fees. The City schedules list ADUs at $2,991 for parks and $1,491 for transportation outside downtown.
Olympia WA ADU Impact Fee Rules
Some RestrictionsOlympia Municipal Code § 15.04.040
Per RCW 36.70A, for each category of impact fees, the impact fees imposed on Accessory Dwelling Units may not exceed 50 percent of those assessed for a single-family residence or principal unit on the same lot. ... C. The following development activities are not subject to some or all impact fees: ... 6. The creation of an accessory dwelling unit is not subject to school impact fees.
Shed & Carport Rules
In the City of Olympia, Washington, detached accessory structures are allowed in all residential districts but cannot be built before the main building, must stay incidental to the lot, and are capped at 800 square feet each in districts of twelve units per acre or less. Detached garages and carports follow a 1,200 square foot limit per dwelling unit.
Olympia WA Shed and Accessory Structure Rules
Some RestrictionsOlympia Municipal Code § 18.04.060(B)
Accessory structures are detached structures and are permitted in all residential districts subject to the following requirements: 1. Time of Establishment. Accessory structures may not be built prior to commencing construction of the main building on the lot. However, lots may be created which contain an accessory structure (without an associated primary use) constructed prior to submission of...
Garage Conversions
In the City of Olympia, Washington, a detached garage can be converted into an accessory dwelling unit even if it violates current setback or lot coverage rules, provided it was legally established and either built before December 22, 2025 or at least 10 years before the application. The ADU portion is capped at 1,000 square feet.
Olympia WA Garage Conversion to ADU Rules
Some RestrictionsOlympia Municipal Code § 18.04.060(A)(5)
5. Converting Existing Structures. ADUs may be created by converting existing legally established structures constructed prior to December 22, 2025, or that were constructed at least 10 years prior to the application for conversion, including detached garages, even if they violate current code requirements for setbacks and/or lot coverage. The existing structure may be added onto as part of the...
Tiny Homes
In the City of Olympia, Washington, tiny houses are tied to the International Residential Code: OMC 16.04.020(A)(2) adopts Appendix Q, Tiny Houses, along with the radon, solar-ready and dwelling unit sprinkler appendices. Separately, OMC 16.06.020 bars living, sleeping or cooking in a recreational vehicle parked on public or private property, with listed exceptions.
Olympia WA Tiny House Rules Under IRC Appendix Q
Some RestrictionsOlympia Municipal Code § 16.04.020(A)(2)
2. International Residential Code Adopted. The current State adopted edition of the International Residential Code (“IRC”), as published by the International Code Council, Inc., as adopted by the State Building Code Council in Chapter 51-51 WAC (excluding Chapter 1, Section R112, Board of Appeals, Chapter 11, and Chapters 25 through 43), except that Chapter 29, Section P2904 is adopted and the ...
Looking for Thurston County county-wide rules?
County ordinances apply to unincorporated areas and may supplement Olympia city rules.
Accessory Structures in Thurston County →