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

At a glance

Building permit

Required for residential construction; single-story tool or storage sheds under 200 square feet are exempt¹

Zoning

Spokane County's zoning code applies in unincorporated areas; standards vary by district and use⁴

Septic permits

Spokane Regional Health District permits and inspects systems below 3,500 gallons per day⁵³

Owner-builder exemption

Available from contractor registration for work on your own property, except work done to sell, demolish, or lease it; permits still apply⁶

RV living

An RV occupied continuously for more than 30 days must meet manufactured-home or commercial-coach requirements⁷

Tiny home

Allowed up to 400 square feet if built to the Washington State Building Code, with local approval depending on where it's placed⁸

Minimum dwelling size

190 square feet of habitable space minimum, with at least one room of 120 square feet or more⁹

Private well

Some small-quantity uses are exempt from a water-right permit, but even an exempt well requires a notice of intent¹⁰

Who to call

Contact details are copied from each office’s official page and were checked against it on October 12, 2026.

Do you need a building permit 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 Code¹¹¹². Washington's state building code applies except where state law provides otherwise¹³. 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 rules¹⁴.

Who is the Spokane County building department, and how do you reach them?

The Spokane County Building & Planning Department evaluates and issues land-use and building permit applications and enforces site-development regulations governing building use and occupancy¹⁵. The office is at 1026 W Broadway Avenue, 1st Floor, Spokane, WA 99260, and the phone line is 509-477-3675¹⁶. The county accepts online building-permit applications for unincorporated Spokane County, Millwood, Rockford, and Spangle¹⁷. Cheney and Medical Lake issue city building permits; Millwood also requires written city permission for the building work and use changes covered by its code¹⁸¹⁹²⁰. 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 review²¹. 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 minimum²². 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 staff²³.

Does Spokane County have zoning?

Spokane County's zoning text and maps govern unincorporated land; the mapped district determines allowed uses and development standards⁴²⁴²⁵. 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^2627285. 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 Lands²⁹. 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 acre³⁰. Rural cluster building coverage is capped at 35% in Rural-5, Rural Traditional, and Rural Conservation, and 50% in Urban Reserve³¹. 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 setback³². Ask Building & Planning for the parcel's applicable table.

How do septic permits work in Spokane County?

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 agencies³³³⁴. The Septic Systems line is 509.324.1560 ext. 1, and the office is at 1101 W. College Ave., Spokane, WA 99201³⁵. SRHD inspects systems after installation and requires inspection and maintenance before renewing the operating permit³⁶. Conventional gravity systems require inspection every three years, while other on-site systems and holding tanks require annual inspection³⁷. Only 2.6% of county soils lack severe limits for a conventional drain field, so arrange the site evaluation before fixing the house location³⁸. Each property must connect to county sewer and abandon its septic tank within one year of being notified that sewer service is available³⁹. 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 utilities⁴⁰.

Can you live in an RV or tiny home on your land in Spokane County?

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 zone⁴¹. 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 area⁴².

Building a home in Spokane County: the steps, in order

1. Ask Spokane County Building & Planning for the parcel's zoning district, development standards, and subdivision status²⁵⁴³.
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 connections⁴⁰.
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 limits⁴⁴³⁸.
4. Have the Division of Engineering and Roads review driveway-approach work and determine which permits apply⁴⁵.
5. Submit the project-specific plans and supporting documents required for the residential building-permit application⁴⁶.
6. Build to the adopted construction codes and complete the required reviews; final approval is required before the permitted structure may be used or occupied¹²⁴⁷.
7. Keep the permit timeline in view: a building permit expires after three years unless the Director grants one extension of up to 180 days¹⁷.

What to check before you buy land in Spokane County

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 type⁴⁸⁴⁹. 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 system³⁸. 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 permit⁵⁰. 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 location⁵¹. A driveway connecting to a county public road needs an approach permit, and installation must be inspected and accepted before dwelling occupancy⁵². 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.

Watch-outs

• Dividing unincorporated Spokane County land involves separate plat or short-plat review and fees; a preliminary plat has a published base fee of $8,227.25 plus $22.77 per lot⁵³.
• Washington's tiny-house allowance is written for structures built to the state building code; a wheeled structure that doesn't meet that definition may instead be regulated as a recreational vehicle or park model, with different rules⁸.

Sources

1. Residential Building Permits, quoted and re-checked
2. County Code, quoted and re-checked
3. New Systems or Changes to Existing Systems, quoted and re-checked
4. County Code, quoted and re-checked
5. Septic Systems, quoted and re-checked
6. RCW 18.27.090: Exemptions, quoted and re-checked
7. Spokane County Code § 3.12.010, Occupancy restrictions, quoted and re-checked
8. Tiny Houses (Washington statewide rule), quoted and re-checked
9. WAC 51-50-1208, Section 1208—Interior space dimensions, quoted and re-checked
10. Exempt Wells, quoted and re-checked
11. Frequently Asked Questions — construction codes, quoted and re-checked
12. spokanecounty.gov, quoted and re-checked
13. app.leg.wa.gov, quoted and re-checked
14. RCW 18.27.090: Exemptions, quoted and re-checked
15. 2026 Land Use Fee Schedule BP-4P, quoted and re-checked
16. Spokane County Building & Planning Department (spokanecounty.gov)
17. Spokane County Building & Planning - Frequently Asked Questions (spokanecounty.gov)
18. Cheney: Building Department (Spokane County), quoted and re-checked
19. Medical Lake: Building Department - City of Medical Lake (Spokane County), quoted and re-checked
20. Millwood: Millwood Municipal Code § 17.44.040—Permit required for erection or alteration (Spokane County), quoted and re-checked
21. Residential Building Permits, quoted and re-checked
22. Building Department Fee Schedule, quoted and re-checked
23. 2026 Land Use Fee Schedule BP-4P, quoted and re-checked
24. Spokane County Zoning Code, quoted and re-checked
25. Spokane County Zoning Code, quoted and re-checked
26. Cheney: Laws & Regulations (Spokane County), quoted and re-checked
27. Medical Lake: Planning & Zoning Department - City of Medical Lake (Spokane County), quoted and re-checked
28. Millwood: Millwood Municipal Code Title 17, Appendix A—Definitions (Spokane County), quoted and re-checked
29. Spokane County Zoning Code, 2025 Printing, quoted and re-checked
30. Spokane County Zoning Code, 2025 Printing, quoted and re-checked
31. Spokane County Zoning Code, 2025 Printing, quoted and re-checked
32. Spokane County Zoning Code, quoted and re-checked
33. Septic Systems, quoted and re-checked
34. New Systems or Changes to Existing Systems, quoted and re-checked
35. Spokane Regional Health District (SRHD) - On-Site Sewage (Septic) Systems (srhd.org)
36. New Systems or Changes to Existing Systems, quoted and re-checked
37. On-Site Septic Operations and Maintenance, quoted and re-checked
38. Share of soils USDA rates "not limited" for a conventional septic drain field (SSURGO). A strict rating: the median county is about 6% and a tenth of counties are 0%, so a low figure means most lots need a site evaluation or an engineered system, not that septic is impossible. Cite it only with that caveat: Bolthole Index county data
39. spokanecounty.gov, quoted and re-checked
40. Residential Building Permits, quoted and re-checked
41. Spokane County Zoning Code, quoted and re-checked
42. Spokane County Zoning Code, Accessory Dwelling Unit Standards, quoted and re-checked
43. Residential Building Permits, quoted and re-checked
44. New Systems or Changes to Existing Systems, quoted and re-checked
45. Residential Building Permits, quoted and re-checked
46. Residential Building Permit Application, quoted and re-checked
47. Residential Building Permits, quoted and re-checked
48. County Code, quoted and re-checked
49. Spokane County Building & Planning FAQs, quoted and re-checked
50. Floodplain Information, quoted and re-checked
51. Floodplain Requirements, quoted and re-checked
52. Driveways, quoted and re-checked
53. 2026 Land Use Fee Schedule BP-4P, quoted and re-checked

Written October 12, 2026 from the rules quoted below, each taken from an official source and re-checked by an independent reviewer. This is research, not legal advice: rules change, so confirm with the office before you buy or build.