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

Yes, for most construction. The Wahkiakum County Building Permit Application Packet is required for houses, tiny houses, pole barns, sheds, or any other structure converted to a permanent residence¹. A permanent residence must have plumbing, conditioned air, potable water, and Environmental Health-approved sewer or septic before you can apply¹. A detached structure used only recreationally, without plumbing or conditioned air, does not need a building-permit application and cannot be used as a permanent residence¹. Work in unincorporated Wahkiakum County that changes a structure's occupancy classification requires a building permit and inspection⁷. Wahkiakum County enforces the 2021 International Building, Residential, Mechanical and Fire Codes, the 2021 Uniform Plumbing Code, and the 2021 Washington State Energy Code with Washington amendments⁸. Washington's owner-builder exemption permits owners to work on their own property without contractor registration, but building permits still apply and the exemption does not cover work for sale, demolition, or lease⁵. Qualifying work tied to farming, dairying, agriculture, horticulture, livestock or poultry also has a contractor-registration exemption, but that exemption does not waive Wahkiakum County building permits^1,5.

For unincorporated land, Wahkiakum County's Building & Planning Department is at 64 Main Street, Cathlamet, WA 98612; reach the building inspector at hicksd@wahkiakumcounty.gov, office line 360-795-6100 extension 104, or work cell 360-353-8074¹. Call ahead to confirm the required documents; applications and building documents may be emailed, and the county will not process an incomplete submission¹. Inside the incorporated Town of Cathlamet, obtain the building permit from the town clerk before erecting a building². County building permit fees are published: a new residence between 120 and 1,000 square feet runs $506.50, and one between 1,001 and 2,000 square feet runs $606.50, with the schedule's additional $4.50 building-permit fee⁹. A flood-elevation certificate, SEPA application, or JARPA application may also be required depending on the unincorporated property's location¹. If a driveway intersects a county road, Public Works handles the separate County Road Approach permit application at tobinj@wahkiakumcounty.gov¹.

No. Cathlamet is the only incorporated town inside Wahkiakum County, and the rest of the county is unincorporated and has no county zoning districts^3,6. The Town of Cathlamet has its own Title 19 zoning, so land inside town limits is governed differently³. Because unincorporated Wahkiakum County has no zoning ordinance, county zoning does not restrict accessory dwellings or temporary camping there; building-code, septic, shoreline, floodplain and other non-zoning rules can still apply³. Unincorporated Wahkiakum County has no minimum dwelling size, lot-coverage limit, or building-height limit imposed solely through county zoning⁶. House setbacks are 30 feet from mean high water, 5 feet from a side lot line, and 15 feet from a road right-of-way line; some reductions may be available through a variance or the responsible department¹⁰. Residential lots need at least 1 acre with a well and septic or 1/2 acre with public water and septic⁶. Land division also requires county approval under the applicable short-plat or subdivision process¹.

Wahkiakum County Health and Human Services issues septic installation permits for new construction and repairs⁴. Every application must include two copies of a septic-system design prepared by a licensed on-site wastewater treatment system designer or professional engineer⁴. The county requires test pits so the county and designer can evaluate the soil and choose the system type⁴. The local health officer must inspect permitted on-site sewage work, and the system must be inspected before cover; ongoing inspections are at least every 3 years for a sewage tank with a gravity soil dispersal component and annually for other systems unless the health officer requires more frequent checks¹¹. A permanent residence cannot obtain a building permit until Environmental Health approves sewer or septic and potable water is confirmed¹. Only 6.8% of Wahkiakum County soils have no severe limitation for a conventional drain field, so complete the site and soil evaluation before committing to a house location¹². Environmental Health is at 42 Elochoman Valley Road, Cathlamet, WA 98612⁴.

Unincorporated Wahkiakum County has no county zoning restriction on temporary camping, but an RV used as a permanent residence must have its own potable water and sewer or septic^1,3. A tiny house used as a permanent residence requires the county building-permit packet plus plumbing, conditioned air, potable water, and approved sewer or septic¹. Washington defines a code-built tiny house as no more than 400 square feet, including its kitchen, bathroom, and sleeping area¹³. Unincorporated Wahkiakum County adds no minimum dwelling size solely through zoning, although the building code and other site rules still apply⁶. A manufactured home needs a county placement permit, foundation specifications, engineered anchoring, approved septic and water, and a title-elimination permit; the title-elimination requirement also applies inside Cathlamet¹.

1. Confirm whether the parcel is inside Cathlamet: the town clerk issues building permits in town, while county Building & Planning handles unincorporated projects^1,2.
2. For unincorporated land, check that the lot and house location can meet the applicable minimum lot size and setbacks before finalizing plans^6,10.
3. Start the septic site and soil evaluation with Wahkiakum County Health & Human Services; test pits come before system design⁴.
4. Have a licensed designer or professional engineer prepare the septic design, then secure Environmental Health approval and confirm potable water^1,4.
5. Call county Building & Planning before submitting an unincorporated application, confirm every required document, and email the application and building documents if convenient; incomplete applications are not processed¹.
6. Obtain a County Road Approach permit through Public Works if the driveway intersects a county road¹.
7. Ask whether the property's location also requires a Flood Elevation Certificate, SEPA application, or JARPA application¹.

Check the soil before you assume a standard septic system will work: only 6.8% of Wahkiakum County's soils carry no severe limitation for a conventional drain field, so a site and soil evaluation matters before you commit¹². Confirm the parcel is outside Cathlamet if you're counting on no zoning review; land inside the town is governed by Title 19 zoning instead³. If the tract you're buying was recently split from a larger parcel, ask whether it went through the county's short-plat or subdivision process, which applies to any division into four or more parcels where the smallest lot is under five acres¹. Terrain here is steep by rural standards: only 28.2% of the county sits at 15% slope or less, while 85.1% is forested, so grading and access can matter as much as soils¹². Rainfall is heavy, at about 81.7 inches a year, with severe drought in only 4.8% of years, which favors a well but means drainage and site grading deserve real attention¹². If your driveway will connect to a state highway rather than a county road, you need written permission from the Washington Department of Transportation before building it, separate from the county's Road Approach permit¹⁴. Budget for carrying costs too: the effective property tax rate runs about 0.6%, with a median annual bill near $2,084, against a typical home value around $405,190¹².