Sonoma County, CA Accessory Structures: Tiny Homes (2026)

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.