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

California distinguishes between two categories of tiny homes. A tiny house on a permanent foundation, meeting the CBC (CRC) and California Title 24 energy code, is treated as a regular dwelling unit or ADU. If under 500 sq ft and built within the walls of an existing single-family home, it qualifies as a JADU under Gov Code §65852.22; if up to 850 sq ft and detached or converted, it qualifies as a standard ADU under §65852.2. Full building permit and plan check are required from Riverside County Building and Safety. A tiny house on wheels (THOW) is a vehicle and is regulated by the California Department of Housing and Community Development (HCD) or the DMV depending on certification. Under Gov Code §65852.2(j), a THOW may be treated as an ADU only if it meets the 'Movable Tiny House' ANSI 119.5 standard and is certified by HCD; even then, Riverside County has local discretion on whether to allow them as ADUs. THOWs not meeting those standards are recreational vehicles and can only be occupied in permitted RV parks or short-term in emergency declarations. Using a travel trailer as a full-time residence on an unincorporated lot violates Ord. 348 and is routinely cited by Code Enforcement.