ADU (accessory dwelling unit) Rules in Clatsop County, OR: What to Check
A practical Clatsop County, OR ADU guide: how zoning, lot type, utilities, and site constraints shape eligibility, and what Wolf verifies on your exact parcel first.
Whether you can build an ADU (accessory dwelling unit) in Clatsop County depends on the parcel’s zoning, lot type, and site conditions. Before you look at models, confirm which rules and fee schedule apply to your address.
Where ADUs are allowed
County and city rules differ. Start with the permit authority for the address, and don’t apply county standards automatically to Astoria, Warrenton, Seaside, Cannon Beach, or Gearhart.
The county’s April 2026 Article 3 places ADUs in section 3.0180. It distinguishes AC-RCR, RC-MFR, and RCR properties served by approved sanitary sewer from rural residential parcels. The ordinary rural path includes at least two acres, a primary dwelling, a 900-square-foot maximum gross habitable floor area, and siting within 100 feet measured between the closest exterior walls.
The rural path also requires water, wastewater, fire service and access review, prohibits vacation occupancy with a recorded covenant, and prevents a land division separating the homes. A separate historic-home provision has different conditions.
Check the use table and full standards for the parcel. An older summary used a proportional size limit; the current standard is 900 square feet, so don’t carry an old percentage into model selection.
Site and code factors that shape an ADU
On Clatsop County properties, these usually decide whether an ADU works and how big it can be:
- Applicable floor-area limit and how the county measures it
- Setback requirements from property lines and other structures
- Height restrictions, which can depend on location and setbacks
- Water and sewer connections, or septic system capacity
- Electrical service upgrades
- Access and any applicable parking requirements; the current Article 3 table lists zero spaces for an accessory dwelling
The exact square footage caps, setback distances, height limits, and parking counts depend on your zoning and parcel. Verify them before you lock in a design or a price. Two properties a few miles apart can get different answers because of septic capacity, slope, access, or utility routing.
What Wolf checks first
For a Clatsop County project, we confirm:
- The parcel’s zoning designation
- Whether an existing lawful dwelling is on the property
- Whether the property can support the ADU’s septic or sewer, water, and electrical needs
- Whether a modular unit can be delivered, staged, and set safely
- Whether a smaller footprint avoids a constraint a larger model would trigger
Modular homes in Clatsop County
Wolf builds modular homes in its factory, off-site. The property still needs local placement, foundation, utility, and inspection approvals from the jurisdiction that reviews your site. For how a home gets over the Coast Range and how other coast counties compare, see Oregon coast ADUs and beach cottages.
Start with the address
Send us your property address and what you want the home to do, such as long-term housing, bringing aging parents closer, or giving extended family a private place to stay. ADU approval does not establish permission for vacation rental use. We’ll start with zoning, access, and utilities, then confirm the county rules for your parcel.
Get a free Wolf property evaluation for your Clatsop County parcel.
Sources
Requirements change, so check the current forms and rules with your jurisdiction before you file. This is general information, not legal advice.