Building permits, zoning and septic rules in Clackamas County, Oregon

Clackamas County requires multiple permits for a new single-family home or duplex, and most additions or modifications to an existing home or duplex also require permits¹. The county building code incorporates Oregon's structural, residential, electrical, plumbing, mechanical and other specialty codes¹⁰. A qualifying agricultural building on farm- or forest-zoned property can avoid the building permit and building inspections, but land-use approval and electrical, plumbing, mechanical or erosion-control permits may still apply¹¹. The exemption is limited to qualifying agricultural operations, excludes public use and does not cover a dwelling¹². For permitted residential work, final trade inspections occur after the systems are complete and before occupancy, and the final building inspection follows approval of every other required inspection¹³. County building and planning fee schedules are published, but the total varies with permit type, valuation, plan review, inspections and project details¹⁴.

Clackamas County Building Permitting is at the Development Services Building, 150 Beavercreek Road in Oregon City, and can be reached at 503-742-4240¹. Zoning questions and land-use applications go to the Planning Division in the same building, Room #225, at 503-742-4500; planning applications must be filed through Development Direct or in person by appointment². The Septic Program, on the 2nd floor, handles onsite wastewater permits at 503-742-4740⁴. Floodplain development permits also go through the Planning Division¹⁵. Transportation Engineering handles county road right-of-way and engineering matters at 503-742-4691¹⁶. Start with Planning for parcel use and siting, then coordinate with Septic when the property lacks community sewer, and submit the building package through Development Direct¹.

Clackamas County administers state, regional and local zoning regulations in unincorporated areas². Incorporated cities have their own zoning authority, so property inside city limits must be checked with that city rather than the county; septic permits remain a separate county program^3,4. The county's zoning ordinance divides unincorporated land into districts shown on zoning maps, so look up the parcel's district first¹⁷. The parcel's district matters: manufactured dwellings are primary uses in several urban districts, while other urban districts prohibit them¹⁸. In the RA-1, RA-2, RR, RRFF-5, FF-10 and FU-10 rural and future-urban residential districts, a manufactured dwelling is a primary use, but each lot of record may generally hold only one principal dwelling, and zoning, building, floodplain and septic standards still apply¹⁹. A rural accessory dwelling unit outside an urban growth boundary and unincorporated community requires a lot of at least 2 acres, is generally capped at 900 square feet, must sit within 100 feet of the primary dwelling and cannot be a short-term rental²⁰. A tiny home on wheels or similar mobile structure cannot serve as that ADU⁹. Resource-land minimums are generally 80 acres for exclusive farm use or forestland and 160 acres for rangeland, subject to statutory exceptions⁸.

The Clackamas County Septic Program regulates installation, repair and maintenance for homes and businesses not served by community sewer⁴. Replacing, repairing, altering or installing a septic system requires a construction permit; most permit types require an approved site evaluation, and a new system or alteration also requires a Land Use Compatibility Statement²¹. A buildable lot needs direct access to sanitary sewer or an approved onsite sewage disposal system²². A composting toilet does not eliminate the need for an approved wastewater system for the home's remaining wastewater²³. An RV approved as a second dwelling must connect to sanitary sewer or a county-approved onsite wastewater system and have a working sink and toilet connected to that system⁷. Only 7.1% of county soils rate free of severe limits for a conventional drain field, making a site evaluation an important pre-purchase step⁵. An ADU, guest house, RV, bedroom addition or hardship dwelling using an existing system can trigger a professional inspection and Existing System Evaluation Report⁴.

Unincorporated Clackamas County can approve one RV as a second dwelling on qualifying single-family residential property, but a Type I land-use application is required, the lot must already have exactly one eligible primary dwelling, and an owner must live there at least six months a year⁷. The approval is valid for 4 years and must be kept active through maintained county development permits⁷. The RV must sit 10 to 100 feet from the primary dwelling, have a written residential rental agreement, connect to approved sewage, potable water and electrical service, and stay outside the Floodplain Management District; neither dwelling may be used as a short-term rental⁷. This second-dwelling route is not general permission to camp on a vacant parcel. The county's separate recreational vehicle camping facility use in the RA-1, RA-2, RR, RRFF-5 and FF-10 districts is a conditional use reviewed under Section 813 and is prohibited in FU-10, so it is a campground-style business use rather than a way to live in an RV on your own lot¹⁹. Oregon allows occupancy of a camping vehicle on private land only with the owner's consent, adequate space for approved water and sewage, and compliance with state and local sanitation and utility standards²⁴. County park rules separately prohibit overnight camping outside designated numbered spaces, but that rule applies to county park areas rather than private land²⁵. A tiny home on wheels cannot be used as an ADU, and we could not confirm one general occupancy classification for every other tiny-home design; ask Planning how the specific unit and parcel will be treated^2,9.

1. Confirm the zoning district, allowed dwelling type and any resource-land minimum by calling Planning at 503-742-4500^2,8.
2. If community sewer is unavailable, obtain the septic site evaluation and Land Use Compatibility Statement needed for the proposed system²¹.
3. Identify the building, electrical, plumbing and mechanical permits the project requires, review the published fee schedules, then submit the drawings through Development Direct^1,14.
4. Show the driveway and adjacent streets on the site plan, and obtain a floodplain development permit before work if the site is in the Floodplain Management District^1,15.
5. An owner who is not licensed with the Construction Contractors Board must sign the construction-responsibility statement before a residential permit can issue; hired subcontractors must hold the required licenses, and the permit cannot be transferred^6,26.
6. The separate owner-built structural exemption is narrow: it covers ceiling heights, room sizes and specified temperature requirements, does not remove the permit requirement, and may require the permit to be recorded with the county clerk²⁷.
7. Complete every required trade inspection before the final building inspection and occupancy¹³. A certificate of occupancy is expressly required for new commercial, industrial and multi-family development, but the county source does not extend that requirement to an ordinary single-family home²⁸.

From the county's center, the nearest city of 100,000 or more people is about 23 miles away, and Clackamas County has a population density of about 226 people per square mile⁵. Federal land covers 53.4% of the county, so confirm that any parcel offered for sale is privately owned and legally buildable⁵. About 83% of the land is wooded and just over half sits at a gentle 15% slope or less, so expect clearing and grading questions on a wooded, sloped parcel⁵. Because only 7.1% of Clackamas County soils rate free of severe limits for a conventional drain field, budget for a site evaluation before closing on land without sewer⁵. For a private well, ordinary domestic groundwater use up to 15,000 gallons a day does not require a water-use permit, but well-construction standards still apply²⁹. A landowner drilling or altering a well personally generally needs a landowner permit, fee and financial bond before work unless licensed as a Water Supply Well Constructor³⁰.