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

Yes. Most new construction, remodeling and repair work affecting a building or structure in Cowlitz County requires a permit¹. Cowlitz County administers adopted construction codes as minimum standards; electrical permits come from Washington Labor and Industries¹. After work begins, a permitted project must receive an inspection every 180 days or the permit expires; additional project-specific inspections may apply⁸. The county adopts planning and building fees annually; its 2026 schedule took effect July 1, while Environmental Health handles septic and water fees¹⁰. An owner working on personal property may be exempt from contractor registration, but the exemption does not waive building, electrical, plumbing or septic permits and does not cover work intended for sale, demolition or lease⁷. Farming-related work also has a contractor-registration exemption, not a blanket exemption from county permits or land-use rules⁷. Inside Woodland, the city handles building permits, including accessory structures at 120 square feet or more; septic review remains with Cowlitz County Environmental Health^3,11.

Cowlitz County Building & Planning is the first stop for building permits, zoning questions, plan review and code enforcement in unincorporated areas¹². Reach the department at 360-577-3052 or permitinfo@cowlitzwa.gov, at 207 N. 4th Ave., Room 119, Kelso, WA 98626¹². The office is open 7am to 5:30pm Mondays through Thursdays and closed Fridays¹². The typical single-family process starts with planning clearance, then moves through building, engineering and fire-code review before permit issuance¹³. Ask for the current fee schedule because projects may involve several reviews and charges¹⁰. Cowlitz County's design criteria include a 12-inch frost depth, residential wind speed of 110 and Seismic Design Category D1¹⁴.

Only part of unincorporated Cowlitz County is zoned; use the county’s EPIC zoning map with Chapter 18.10 to identify the parcel’s district and permitted uses². County development review also considers Comprehensive Plan policies². Inside Kalama, the city sets zoning; septic review remains with Cowlitz County Environmental Health^3,15. Zoning setbacks vary by district, and building, fire and environmental rules can add setbacks¹. Rural residential minimum lots are 1 acre in RR-1, 2 acres in RR-2 and 5 acres in RR-5; AG and FR require 5 acres, while AG-38 requires 38 acres subject to code exceptions¹⁶. These are minimum standards, and sewage, water or other development requirements may be stricter¹⁶. In unzoned areas, the Comprehensive Plan determines minimum lot size and dimensions¹⁷. An accessory dwelling requires planning clearance and a building permit⁹. Washington’s adopted building code requires at least 190 square feet of dwelling habitable space, including a room of at least 120 square feet; we could not confirm a Cowlitz County amendment reducing those requirements¹⁸.

Cowlitz County's Environmental Health Unit administers septic permitting and operation-and-maintenance oversight³. A licensed engineer or on-site septic designer completes the site evaluation; the evaluation, system design, permit application and fee then go to Environmental Health¹⁹. A county permit is required before installing or modifying an on-site sewage treatment component, including new installation, repair, replacement or alteration work³. Final inspection follows submission of the required designer and installer paperwork, and an older system must be verified when connected to a new dwelling or when bedrooms are added³. For ongoing inspections, provider qualifications depend on system type: Level I covers gravity systems, Level II covers all but proprietary systems, and proprietary systems require a manufacturer-approved professional²⁰. Only about 12.8% of Cowlitz County soils are rated without severe limits for a conventional drain field, so make the site evaluation an early feasibility step²¹.

Cowlitz County allows temporary noncommercial use of up to two recreational vehicles or two camping sites on an undivided lot, provided the units are independent or the lot has health-authority-approved potable water and sanitary facilities⁴. That provision does not give permission for permanent RV residence⁴. A temporary campground not tied to permitted construction may operate no more than 14 days, and a construction campground needs a temporary campground permit and may not have permanent utility connections⁴. We could not confirm permission for long-term RV residence on private land in Cowlitz County⁴. Washington's statutory definition describes an RV as temporary, transient quarters that are not occupied as a primary residence, but that definition does not decide private-land siting⁵. Give Building & Planning the parcel number and ask whether RV placement or occupancy is allowed there and for how long¹². Washington defines a tiny house as a unit of no more than 400 square feet on wheels that is built to the state building code, but local requirements still control its foundation, installation and location⁶. Cowlitz County projects involving plumbing typically need water approval, while projects involving bedrooms typically need sewer approval; required approvals go to Building & Planning and vary by utility type and project scope²². A holding tank generally cannot serve new residential development or an expansion except in limited approved situations²³.

1. Apply for planning clearance and confirm the parcel's zoning and district standards with Building & Planning^12,13.
2. Submit the septic design and water application to Environmental Health; these reviews are separate from the building-permit process¹³.
3. Apply for the building permit with plans and required documents, and ask for current building, water and septic fees^1,10.
4. Resolve access: submit a county-road driveway approach application in person to Public Works, or obtain state permission for a state-highway approach^24,25.
5. Obtain a floodplain management permit before development in the floodplain; flood-hazard construction must also comply with county flood-management standards^26,27.
6. Keep approved plans on site and request inspections during construction, never letting more than 180 days pass without one^8,13.
7. Complete the construction, fire and septic inspections and all permit conditions; the Building Official then issues the Certificate of Occupancy¹³.

Start with legal status: confirm whether the parcel lies in the zoned portion of unincorporated Cowlitz County and whether any past division was approved^2,28. County short plats must address potable water, sewage disposal, survey, legal access and environmental compliance²⁸. Next test physical feasibility. Only about 12.8% of county soils are rated without severe limits for a conventional drain field, while about 28.7% of the land has a slope of 15% or less; site-specific septic, grading and drainage work can therefore drive the buildable area²¹. Cowlitz County projects involving plumbing typically need water approval, while projects involving bedrooms typically need sewer approval; required approvals go to Building & Planning and vary by utility type and project scope²². Confirm whether floodplain permitting applies and whether access is from a county road or state highway before closing^24,25,26.