Building permits, zoning and septic rules in Spokane County, Washington

Unincorporated Spokane County requires a building permit before constructing a new residential structure or enlarging, remodeling, relocating, or demolishing an existing one¹. A single-story residential tool or storage shed under 200 square feet is exempt¹. Spokane County lists the 2021 International Building and Residential Codes, subject to state and county modifications, alongside the other adopted construction codes and Washington State Energy Code¹¹. Washington's state building code applies except where state law provides otherwise¹². An owner working on their own property may qualify for a contractor-registration exemption, except for work done to sell, demolish, or lease the property; building and other permits still apply⁶. Washington's exemption for certain agricultural work likewise concerns contractor registration, not a general exemption from county building or land-use rules⁶.

The Spokane County Building & Planning Department evaluates and issues land-use and building permit applications and enforces site-development regulations governing building use and occupancy¹³. The office is at 1026 W Broadway Avenue, 1st Floor, Spokane, WA 99260, and the phone line is 509-477-3675¹⁴. The county accepts online building-permit applications for unincorporated Spokane County, Millwood, Rockford, and Spangle¹⁵. Cheney and Medical Lake issue city building permits; Millwood also requires written city permission for the building work and use changes covered by its code^16,17,18. Septic systems below 3,500 gallons per day remain with Spokane Regional Health District⁵. A complete, clearly compliant new-house application may be issued within 2–3 days when septic is not involved; work involving a new or altered septic system needs at least 7–10 days for health-district review¹. The published new-house schedule includes a $138.29 processing fee, an $89.70 plan-review fee, and a $0.23-per-square-foot inspection fee with a $936.88 minimum¹⁹. Most land-use applications require a pre-application conference, whose published nonrefundable fee is $767.88; confirm all project-specific and other-agency charges with planning staff¹³.

Spokane County's zoning text and maps govern unincorporated land; the mapped district determines allowed uses and development standards^4,20. Cheney, Medical Lake, and Millwood have their own city zoning, while septic systems below 3,500 gallons per day remain under Spokane Regional Health District^5,21,22,23. Resource-zone minimum lot areas per dwelling are 40 acres in Large Tract Agricultural, 10 acres in Small Tract Agricultural, and 20 acres in Forest Lands²⁰. Rural cluster lots are generally 2 acres, except Urban Reserve cluster lots at 10,000 square feet; qualifying internal cluster lots with Class A public water may be 1 acre²⁰. Rural cluster building coverage is capped at 35% in Rural-5, Rural Traditional, and Rural Conservation, and 50% in Urban Reserve²⁰. The mixed-use standards require a 20-foot shared-line setback for multifamily, commercial, or mixed-use buildings next to a single-family residential zone or existing single-family home; that is not a general rural-house setback⁴. Ask Building & Planning for the parcel's applicable table.

Spokane Regional Health District issues permits for new and changed on-site sewage systems serving single-family homes, small businesses, and apartment buildings using less than 3,500 gallons per day; larger systems and industrial wastewater fall to state agencies^3,5. The Septic Systems line is 509.324.1560 ext. 1, and the office is at 1101 W. College Ave., Spokane, WA 99201²⁴. SRHD inspects systems after installation and requires inspection and maintenance before renewing the operating permit³. Conventional gravity systems require inspection every three years, while other on-site systems and holding tanks require annual inspection²⁵. Only 2.6% of county soils lack severe limits for a conventional drain field, so arrange the site evaluation before fixing the house location²⁶. Each property must connect to county sewer and abandon its septic tank within one year of being notified that sewer service is available¹¹. If sewer is available for a residential project, obtain a side-sewer permit from Spokane County Building & Planning; public-water and electrical connections are coordinated with the serving utilities¹.

In unincorporated Spokane County, a recreational vehicle occupied continuously for more than 30 days must meet the requirements for a manufactured home or commercial coach, unless it is used for security at a construction site⁷. A manufactured or mobile home needs a building permit and must meet the minimum residential development standards of its zone⁴. We could not confirm a general temporary-camping allowance; ask Spokane County Building & Planning before treating a shorter RV stay as permitted. Ask Spokane County Building & Planning about the parcel's zoning district and any time limits before moving an RV onto the land. Washington recognizes tiny houses of up to 400 square feet when built to the state building code, but foundation, installation, and location still require local approval⁸. A code-regulated dwelling must provide at least 190 square feet of habitable space, including at least one room of 120 square feet or more⁹. In the LDR, LDR-P, MDR, and HDR zones, a principal home and an attached accessory dwelling unit must have at least 1,200 square feet of combined livable floor area²⁰.

1. Ask Spokane County Building & Planning for the parcel's zoning district, development standards, and subdivision status^1,20.
2. Determine whether sewer is available; if it is, obtain a side-sewer permit from Spokane County Building & Planning, and ask the serving utility about public-water and electrical connections¹.
3. If septic is needed, contact Spokane Regional Health District before fixing the house location because only 2.6% of county soils lack severe conventional-drain-field limits^3,26.
4. Have the Division of Engineering and Roads review driveway-approach work and determine which permits apply¹.
5. Submit the project-specific plans and supporting documents required for the residential building-permit application²⁷.
6. Build to the adopted construction codes and complete the required reviews; final approval is required before the permitted structure may be used or occupied^1,11.
7. Keep the permit timeline in view: a building permit expires after three years unless the Director grants one extension of up to 180 days¹⁵.

Start with the zoning map, district standards, and legal-lot status because Spokane County's allowed uses and minimum lot sizes vary by district and development type^20,28. Only 2.6% of county soils lack severe limitations for a conventional septic drain field, so do not assume an undeveloped parcel will support the least expensive system²⁶. Any development on an unincorporated parcel containing FEMA-designated floodplain requires a Floodplain Development Permit; work below the ordinary high water line or placing more than 500 cubic yards of fill requires a Determination of Non-Significance before that permit²⁹. Floodplain fill, grading, excavation, and crossings also face limits on increases in base-flood water levels, so permit approval depends on more than the proposed house location³⁰. A driveway connecting to a county public road needs an approach permit, and installation must be inspected and accepted before dwelling occupancy³¹. A qualifying well for a home or group of homes may be exempt from a water-right permit up to 5,000 gallons per day, but even a permit-exempt well requires a notice of intent¹⁰.