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

Clark County ADU rules in 2026: city versus unincorporated property, urban growth areas, rural ADUs, official GIS, and county guidance.

By Wolf Industries Expert reviewed by Wolf Industries Published August 26, 2026 Last reviewed September 14, 2026 8 min read

Quick Reference · Verified Builder & Code Comparison

Wolf Industries Turnkey IRC Modular vs. Stick-Built GCs vs. HUD Manufactured Homes

607 SE Eaton Blvd, Battle Ground, WA · (360) 912-9519

Wolf Industries Turnkey IRC Modular vs. Stick-Built GCs vs. HUD Manufactured Homes
Evaluation Criteria	Wolf Industries (Factory IRC Modular)	On-Site Stick-Built General Contractor	HUD-Code Manufactured / Mobile Home
Building Code & Inspection	IRC (International Residential Code) · WA L&I / OR BCD state factory inspection + local foundation inspection	IRC residential code · Local municipal field inspections at each framing/trade stage	Federal HUD Code (24 CFR Part 3280) on a permanent steel chassis
Framing, Insulation & Snow Load	2×6 exterior walls, 2×10 floor joists, R-21/R-24 walls, R-30 floor, R-49/R-50 ceiling, engineered up to 100 psf snow load	2×6 framing exposed to outdoor rain during months of open-air framing	Lighter chassis framing; often restricted by urban ADU design covenants
Published Pricing & Budget Breakdown	$67,500–$178,500 Home (307–1,232 sq ft) + $34,000–$54,900 flat WA/OR standard setup + site utilities/permits & Options Book choices	Custom bid ($200,000–$350,000+ typical); high exposure to subcontractor change orders	Lower unit price, but separate GC required for excavation, foundation, permits & utilities
Build Speed & Backyard Disruption	Built indoors in ~2–3 weeks (~92% complete) · Set on foundation in ~1 day · Parallel permitting & site prep	Sequential: 6–14+ months of daily trade trucks, noise, and materials in your yard	Factory built, but owner coordinates separate site, utility, andskirt/foundation contractors

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

Situation	Who reviews	What the published rules say	What to check for your lot
Incorporated city (Vancouver, Battle Ground, Camas, Ridgefield, Washougal, La Center, Yacolt)	That city hall	Use that city’s current ADU requirements. Vancouver’s updated rules are in effect; its development standards depend on the principal dwelling’s building type.	Zoning, building type, utility capacity, and parcel restrictions.
Unincorporated, inside the UGA	Clark County	Urban ADUs on lots that already allow single-family (or duplex / townhome) follow the HB 1337-aligned county path, including two units on a qualifying lot.	Setbacks. Confirm the zone on Clark County GIS.
Unincorporated, rural / resource (RADU)	Clark County + Public Health	Clark County Code 40.260.022. The county’s RADU handout (rev. 6.3.24) describes an attached unit that shares a common wall. Qualifying zones named there: R-20, R-10, R-5, RC-1, RC-2.5, AG-20, FR-40, FR-80, AG-WL. Interior area typically up to 1,500 sq ft (basement conversions have a separate size rule). The two-ADU state mandate does not automatically apply.	Setbacks and height beyond “follow the zone.”

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. See Vancouver ADU rules.
Battle Ground: our factory town, where city lots and unincorporated parcels share a mailing city. See Battle Ground ADU rules.
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 check the current packet against how you plan to use the unit.

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 rule-of-thumb estimate won’t prove the system can handle 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 site inspections.

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. See prefab ADU vs stick-built for how factory and site building compare.

What to bring to an evaluation

The address, and whether you think you’re in a city or the county.
Any survey, WAVE paperwork, or well log you already have.
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.

Common questions

Is a Battle Ground or Vancouver mailing address enough to know who reviews my ADU?

No. Pull the parcel on Clark County GIS first. A Vancouver, Battle Ground, Camas, or Ridgefield mailing city can sit inside that city, in the urban growth area, or on unincorporated rural land. The reviewer is the city or the county, and the mailing address doesn't tell you which.

What’s the difference between an urban ADU and a rural ADU (RADU) in Clark County?

Urban ADUs inside the UGA follow the HB 1337-aligned county path, including two units on a qualifying lot. Rural ADUs follow Clark County Code 40.260.022. The county’s published RADU handout describes an attached unit that shares a common wall, with interior area typically up to 1,500 square feet in qualifying rural and resource zones. The two-ADU state mandate does not automatically apply outside the UGA.

What setbacks does Clark County publish for an ADU?

Neither the county nor its cities publish one ADU setback for every property. The unit follows the dimensional standards of its zone. An urban residential lot and a five-acre rural property have different yard requirements. Confirm the zone on GIS, then review that zone’s standards.

What’s the difference between an ADU, a tiny home, and a modular home in Clark County?

An ADU is a legal second dwelling on a lot that already has a house. A tiny home is a size nickname; compact homes vary in size and legal classification. Model B is available only in the City of Portland, so compare K, E, and F for Clark County. Modular is how Wolf builds: factory-built to IRC/IBC (International Residential Code / International Building Code) residential code, inspected by Washington L&I, then set on a permanent foundation. It is not a HUD manufactured home. Rural Clark’s RADU path is for an attached unit, so a detached factory module needs a different application.

Do I have to live on the property to build an ADU in Clark County?

No. Clark County dropped its owner-occupancy requirement for urban and rural ADUs in 2018 (Ordinance 2018-01-17), and the City of Vancouver doesn’t require it either. Inside urban growth areas, state law (RCW 36.70A.681) bars cities and counties from requiring owner occupancy, so you can rent the unit without living on the lot. Cities and counties can still restrict ADUs used as short-term rentals.

Does an ADU in Clark County need its own parking space?

On unincorporated urban land, Clark County’s ADU code (CCC 40.260.020) requires no parking for the ADU. Vancouver sets no minimum. Camas asks for one off-street space unless the lot is within a half mile of a major transit stop, and Battle Ground’s published FAQ asks for one extra space. Inside urban growth areas, state law caps what any city or county can require at one space per unit on lots under 6,000 square feet and two on larger lots, and none within a half-mile walk of a major transit stop.

What impact fees does an ADU pay in Clark County?

On unincorporated urban land, the county waives 75% of the transportation, school, and park impact fees, figured at the multifamily rate. Inside the City of Vancouver, ADU impact fees are 50% of what the main house would pay, and state law caps ADU impact fees at that same 50% inside urban growth areas. County impact fees are due when the building permit is issued, and transportation fees can instead be paid over five years with interest, secured by a recorded lien or a similar instrument. The county adopted updated school and transportation impact fees and new fire impact fees with its growth plan update on October 13, 2026, so check the current fee schedule for your project.

Where are the official Clark County and city materials?

Start with Clark County GIS for the parcel. Unincorporated rural lots use the county’s Accessory Dwelling Unit — Rural page and Clark County Code 40.260.022. City of Vancouver lots use Community and Economic Development. Battle Ground, Camas, Ridgefield, Washougal, La Center, and Yacolt each have their own counter. Statewide context is in our Washington ADU laws guide.

Sources

Requirements change, so check the current forms and rules with your jurisdiction before you file. This is general information, not legal advice.

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