Olympia, WA Accessory Structures: Shed & Carport Rules (2026)

Section 18.04.060(B) of the Olympia Municipal Code sets the use standards for detached accessory structures, such as sheds, workshops and garages, in the residential districts of the City of Olympia, Thurston County, Washington. First, an accessory structure cannot be built prior to commencing construction of the main building on the lot. The one carve-out is subdivision: lots can be created which contain an accessory structure, without an associated primary use, if it was constructed prior to submission of the subdivision application.

Second, the structure must be clearly incidental and subordinate to the use of the lot, for example storage of personal property or the pursuit of hobbies, or it must be used for agricultural purposes. In residential districts with a maximum density of twelve units or less per acre, each accessory structure cannot exceed 800 square feet. Two exceptions apply: structures accessory to an agricultural use on a parcel one acre or larger, and garages and carports.

Detached garages and carports have their own cap of 1,200 square feet of floor space per dwelling unit, unless approved as a conditional use. A larger garage or carport can be permitted as a conditional use in the districts specified in Table 4.01 if it will not be adverse to the public interest and is compatible with the surrounding neighborhood. When it is visible from the right of way other than an alley, its appearance must be consistent with the primary structure, with a similar roof pitch, building materials and color, and it must meet OMC 18.175.060. The Director or the Director's designee sets a maximum size for each garage that receives conditional use approval. Accessory structures in mobile home and manufactured home parks follow OMC 18.04.060(P)(4) instead. Separate from this zoning section, OMC 16.04.040(A)(1) amends the building code so that a one-story detached accessory structure used as a tool and storage shed or playhouse is exempt from a building permit when its floor area is not greater than 200 square feet.