Building permits, zoning and land rules in Clark County, Washington

Unincorporated Clark County requires building permits for covered construction under building codes adopted and updated statewide¹. Clark County inspects permitted construction and completed plumbing and mechanical work^7,10. An owner working on their own property may be exempt from contractor registration unless the work is for sale, demolition or lease; building permits and inspections still apply^1,7,11. Washington also exempts specified work incidental to agriculture from contractor registration, except work performed by a registered contractor¹¹. Clark County’s separate agricultural building-permit exemption requires a site plan and certifications for a qualifying structure used solely for agriculture or forestry, never human habitation; setbacks, environmental rules, plumbing and mechanical requirements still apply¹².

The Clark County Permit Center handles building permits, inspections and permit status for unincorporated Clark County¹³. Applicants use an LMS account to create the building permit, pay initial fees, submit for processing, schedule a virtual submittal appointment and upload plans in ProjectDox⁴. Clark County requires appointments rather than walk-ins and may charge $148 for each missed submittal appointment; review and inspection fees depend on the project^1,4. Woodland, which lies mainly in Cowlitz County and reaches into Clark County, issues its own accessory-structure building permits¹⁴. Septic administration for Clark County addresses stays with Clark County Public Health³.

Title 40 regulates property development in unincorporated Clark County; incorporated municipalities may administer separate land-use rules². Clark County publishes agricultural, forest, rural, residential, commercial, employment and overlay districts, so find the parcel's exact district before choosing a house plan or use². In the FR-80, FR-40 and AG-20 districts, the cited table sets a 50-foot front setback, a 25-foot street-side setback and 50-foot interior-side and rear setbacks, subject to its footnotes¹⁵. The same districts cap residential buildings at 35 feet¹⁵. Urban lots in specified residential or multifamily zones may support up to two accessory dwelling units with one single-family residence, subject to the county's other conditions¹⁶. Clark County regulates land divisions and short plats, with procedures and standards varying by district and project type; ask Development Review about a proposed split before buying land to divide^2,7.

Clark County Public Health administers on-site sewage systems, and an on-site sewage permit is required before construction begins^3,17. Septic design must account for wastewater loading, soils and surrounding topography³. Only about 15% of Clark County soils are rated without severe limitations for a conventional drain field, so settle septic feasibility before fixing the house location⁵. Conventional gravity systems require inspection every 3 years, pressure distribution systems every 2 years and advanced systems every year¹⁸. A homeowner may inspect a conventional gravity system after taking the Public Health course and passing the $20 operations-and-maintenance test³. A property using on-site sanitation must have an approved, correctly functioning septic system; we could not confirm that every alternative off-grid method is allowed, so take the proposed design to Public Health^3,18.

We could not confirm a general rule allowing long-term RV occupancy on private land in unincorporated Clark County, so ask Community Development what the parcel's district allows². In the floodway, RV occupancy is limited to May 1 through October 1 of the same year; in the floodway fringe it must be fewer than 180 consecutive days, with licensing, mobility and connection conditions¹⁹. Washington recognizes tiny houses of up to 400 square feet when built to the state building code, but the local approval path depends on where and how the home is built⁹. For an urban ADU, public water and sewer are required unless the owner obtains a water-and-sewer waiver¹⁶. Clark County lists a 150-square-foot minimum for specified ADU and cottage-housing categories, not every dwelling; ask Building Safety how the applicable building-code space requirements affect the proposed plan^8,13,20. An urban ADU needs a certificate of occupancy from Clark County Building Safety before anyone moves in¹⁶.

1. Confirm the parcel’s Title 40 district, proposed use and any land division with Clark County Development Review^2,7.
2. Resolve septic design and obtain an on-site sewage permit before construction if the property will use septic^3,17.
3. For a private well, Washington’s domestic water-right permit exemption covers up to 5,000 gallons per day per project, with withdrawals from multiple wells aggregated; local limits still apply, and Ecology requires a drilling notice²¹.
4. If regulated floodplain crosses the property, request an inquiry review when no development enters it, or floodplain permit review when development enters its boundary¹⁹.
5. Resolve road access separately: a county-road approach needs county permission, while work on a state-highway right-of-way needs written WSDOT permission^22,23.
6. Submit the online building-permit application and plans, attend the required appointment and complete building, plumbing and mechanical inspections^4,7,10.