Sonoma County, CA Accessory Structures: Tiny Homes (2026)
Tiny home rules in Sonoma County, CA, 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
- On a foundation
- Permitted as an ADU under Sec. 26-88-060 (ministerial)
- Max size as ADU
- Generally 1,200 sq ft; at least 800 sq ft protected
- Within home/garage
- Up to 500 sq ft may qualify as a JADU (Sec. 26-88-061)
- Tiny homes on wheels
- Treated as RVs/movable units, not permanent dwellings
- Rentals
- 30+ day rentals only; no vacation/transient use
Summary
A permanently sited tiny home on a foundation is typically permitted in unincorporated Sonoma County as an ADU under County Code Sec. 26-88-060 (max generally 1,200 sq ft), processed ministerially. Movable tiny homes on wheels and RVs are not treated as permanent dwellings and face separate restrictions.
According to the 2018 International Residential Code (IRC), a tiny house is a dwelling that is 400 square feet or less in floor area excluding lofts. Stick-built/traditional/site-constructed homes: A small home constructed entirely at the building site. Manufactured houses (commonly referred to as mobile homes): Homes built in a factory mounted on a non-removable steel chassis or frame. Factory-built houses (commonly referred to as modular homes): Factory-constructed homes that are transported to a permanent location for installation on a foundation. Transportable Housing Units and Recreational Vehicles: Travel trailers, motor homes, park model homes, truck campers, camping trailers, or any other housing on wheels. Temporary occupancies of travel trailers, recreational vehicles (RVs), transportable housing units (tiny homes), and manufactured homes are allowed in Sonoma County with a Temporary Occupancy (TEM) permit under the following circumstances: During the construction or major remodeling of a single family dwelling.
Full Breakdown
Sonoma County does not have a stand-alone 'tiny home' ordinance; tiny homes are regulated through the County's existing accessory dwelling unit and building rules. A tiny home built on a permanent foundation and meeting building-code standards for living, sleeping, cooking, and sanitation can qualify as an ADU under Sonoma County Code Sec. 26-88-060, which is processed ministerially with a building permit and any needed septic/water permits. As an ADU, a detached tiny home is generally allowed up to 1,200 square feet (with at least 800 square feet protected), with 4-foot side and rear setbacks and a detached height limit of 18 feet or the base zoning accessory-structure limit.
Tiny homes within an existing single-family dwelling or attached garage and under 500 square feet may instead qualify as a Junior ADU under Sec. 26-88-061. Tiny homes on wheels (THOWs) are generally classified as recreational vehicles or movable units rather than permanent dwellings, and using an RV or movable tiny home as a primary residence is restricted under County rules; some such units are addressed through emergency-housing or caregiver provisions rather than as ADUs. Like all ADUs and JADUs, a tiny-home ADU cannot be used as a vacation or transient rental and may be rented only for 30 days or longer.
Violations & Fines
Living full-time in an RV or tiny home on wheels outside permitted circumstances, or installing a tiny home as a dwelling without ADU/building permits, can result in code enforcement.
Frequently Asked Questions
Can I live in a tiny home in unincorporated Sonoma County?
Is there a special tiny-home ordinance in Sonoma County?
Sources & Official References
Other rules in Sonoma County
California rules heatmap·Compare Sonoma County to another location·View the California accessory structures overview
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