Clark County, WA ADU (accessory dwelling unit) Rules and Regulations (2026)

Clark County is Wolf’s home county. The factory is at 607 SE Eaton Blvd in Battle Ground. That doesn’t mean every Clark County permit follows the same path. A Vancouver mailing address can sit inside city limits, in the urban growth area, or on a five-acre rural parcel that needs a WAVE form before anyone picks finishes.

Who reviews the permit comes first, then the published county and city requirements. Wolf builds ADUs across Clark County. Statewide requirements are in the Washington ADU laws, and planning ranges are in the Washington ADU cost guide.

Who reviews your ADU

Pull the parcel on GIS before you sketch a backyard. It shows the zone, taxlot, city limits, and often prior permits. It won’t show site access issues like a cedar in the crane’s path, but it will keep you from filing with the wrong jurisdiction.

City vs unincorporated

Inside an incorporated city, the city sets the building and zoning path:

• Vancouver: ePlans, with city and county jurisdiction varying around Salmon Creek and Felida.
• Battle Ground: our factory town, where city lots and unincorporated parcels share a mailing city.
• Camas: see Camas ADU rules 2026.
• Ridgefield, Washougal, La Center, and Yacolt: smaller counters, each with its own rules. Brush Prairie is unincorporated Clark County and files with the county.

Unincorporated lots, including Hazel Dell, Minnehaha, Brush Prairie, Hockinson, Fargher Lake, Amboy, and parts of Salmon Creek, file with the county even when the mailing city is Vancouver or Battle Ground.

UGA vs rural / RADU

Inside the urban growth area, Washington’s HB 1337 protections apply to qualifying development. Critical areas, sewer availability, and other statutory exceptions can limit that path; see the Washington ADU laws guide. County Code 40.260.020 allows up to two ADUs on qualifying lots and requires public sewer and water unless the specified waiver applies. The city or county reviews the site plan and issues the permits. We coordinate that process for your project.

Outside the UGA, rural accessory dwelling units follow a separate county process. Official RADU materials describe an attached unit: an internal conversion, an addition to the house or an attached garage, conversion of an attached garage, or inclusion in a new single-family dwelling. A detached factory module does not follow that handout. County forms also distinguish hardship dwellings and guest houses from standard urban ADUs and RADUs, so the current packet needs to be reviewed for the intended use.

For a proposed rural backyard cottage, confirm early whether the unit must share a wall with the primary home to qualify under the RADU rules.

Utilities and the WAVE form

On a sewered city lot, utilities are usually laterals, a cleanout, and whether the panel can pick up a second all-electric dwelling. On a rural Clark County lot, Clark County Public Health has to sign off before a building permit issues.

The county’s RADU page requires a Septic System Release / Water Adequacy Verification (the WAVE form) before the building permit. If Clark Public Utilities water is available, the utility must document that availability. Public Health and the septic designer need to review the existing approval, proposed use, and site conditions; a general per-person estimate cannot establish capacity for another dwelling.

That can mean a drainfield expansion or a new system, so get the septic scoped before you settle on a floor plan.

How a factory-built ADU is treated

A Wolf home is modular. It is not a HUD (the federal standard for manufactured homes) manufactured home. Washington L&I reviews the factory plans and oversees factory inspections; the building must have its L&I insignia before shipping. Local review still covers placement, foundation, utility connections, and applicable site inspections. Confirm the division of inspection responsibilities in the approved permit documents.

The factory and local reviews run in parallel. Factory inspection doesn’t replace Public Health review, a road-approach permit, or the city-vs-county question.

For “tiny home vs ADU vs manufactured” in this county: an ADU is the use and the permit path; tiny is a size nickname; modular is the construction method. HUD manufactured is a different federal code. See prefab ADU vs stick-built for the side-by-side.

What to bring to an evaluation

1. The address, and whether you think you’re in a city or the county.
2. Any survey, WAVE paperwork, or well log you already have.
3. The use: family, long-term rental, guest, hardship, or a cottage you might live in.

We’ll check GIS, identify the reviewer, and determine whether the lot follows city, urban county, or rural ADU rules. Send the address, then compare models that fit the property.

This is general information, not legal advice. Recheck the current statute, local code, and permit packet before you file. Jurisdictions amend forms and effective dates.