Accessory Structures in Spokane County, WA (2026)
3 rules for unincorporated Spokane County, Washington.
Verified from official government sources
ADU Rules
Spokane County allows one accessory dwelling unit (ADU) per single-family lot. Detached ADUs are capped at 800 sq ft on the ground floor and 2 bedrooms, on lots of at least 10,000 sq ft. Attached ADUs are capped at 900 sq ft.
ADU Rules in Unincorporated Spokane County
Some RestrictionsSCC 14.606 (Detached ADU standards)
The accessory dwelling unit shall contain no more than 2 bedrooms and shall measure no more than 800 square feet on the main (ground) floor. Only 1 accessory dwelling unit shall be allowed per lot with an existing single-family residence. Accessory dwelling units shall not be allowed on lots that are less than 10,000 square feet in size.
Shed & Carport Rules
In unincorporated Spokane County, a one-story detached storage shed under 200 sq ft needs no building permit, but must still meet zoning setbacks. Total accessory-structure floor area is capped by lot size under Zoning Code Chapter 14.606.
Shed and Accessory Building Rules
Some RestrictionsSCC 14.606, Table 606-4 (Size Standards for Accessory Structures)
One accessory structure shall be permitted prior to the construction of a primary use. This structure is not for residential occupancy, business use, or outside vehicle repair.
Garage Conversions
Converting a garage or attached space into living quarters is treated as creating an accessory dwelling unit or added living area under Zoning Code Chapter 14.606. It needs a building permit and, if a separate unit, must meet ADU standards and keep required off-street parking.
Garage Conversion Rules in Spokane County
Some RestrictionsSCC 14.606 (Attached ADU standards)
The accessory unit shall be a complete, separate housekeeping unit that is within or attached to the principal unit with a common wall(s). In no case shall it be more than 35% of the building's total livable floor area, nor more than 900 square feet, whichever is less.
All Spokane County ordinances
See every category we cover for Spokane County: parking, noise, fences, fires, animals, pools, and more.
Spokane County Ordinance Hub →