Clark County, WA Accessory Structures: Tiny Homes (2026)
Tiny home rules in Clark County, WA, covering tiny houses on wheels (THOWs), park model RVs, and tiny home on foundation builds, determine where they are legal and how they get permitted.
Key Facts
- State tiny-house size
- 400 sq ft or less
- Permanent residence
- Foundation + building code
- On wheels
- Treated as an RV
- As an ADU
- Must meet CCC 40.260.020/022
- Governing code
- WA State Building Code
Summary
Washington defines a tiny house as a dwelling that may be built on wheels and is no larger than 400 sq ft, excluding lofts. To be a legal permanent residence in Clark County a tiny home generally must sit on a foundation and comply with the Washington State Building Code
A tiny house is a dwelling that may be built on wheels and is no larger than 400 square feet, excluding lofts.
Full Breakdown
Clark County follows the Washington State Building Code, administered by the Department of Labor and Industries. A tiny house on a permanent foundation is regulated as a dwelling and, on a residential lot, typically qualifies as a single-family home or an ADU under CCC 40.260.020/40.260.022, subject to the same size, setback, sewer and water rules. Tiny homes on wheels are classified similarly to recreational vehicles, meaning short-term occupancy only and no long-term rental. Rural hardship placements of a temporary mobile/modular unit may be allowed under CCC 40.260.210 if a qualifying standard is met.
Violations & Fines
Occupying a tiny home on wheels as a permanent residence, or placing a foundation tiny home without permits, violates zoning and building codes and can prompt correction orders and removal.
Frequently Asked Questions
Can I live full-time in a tiny home on wheels in Clark County?
Does a foundation tiny home count as an ADU?
Sources & Official References
Other rules in Clark County
Compare Clark County to another location·View the Washington accessory structures overview
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