Fullerton, CA Accessory Structures: Tiny Homes (2026)

Fullerton Municipal Code section 15.17.100 (Accessory and Junior Accessory Dwelling Units), adopted by City Council on April 7, 2020 to align with state ADU law, is the only practical pathway for a tiny home in residential zones. A tiny house qualifying as an ADU must be on a permanent foundation and meet building code: California has incorporated Appendix AX of the California Residential Code (CRC) since 2020 to specifically govern tiny houses on foundations 400 square feet or less, including loft and ladder/stair standards. Detached ADUs in Fullerton are capped at 1,200 square feet and attached ADUs at 50 percent of the primary dwelling living area or 1,200 square feet, whichever is less. Government Code 65852.2 preempts most local restrictions on ADUs up to roughly 1,200 square feet, and AB 2533 (2024) created a state amnesty pathway for unpermitted ADUs built before 2020 (it does not legalize movable tiny houses). Movable tiny houses on wheels are typically titled as recreational vehicles or park-trailers under California Vehicle Code and HCD rules; Fullerton, like most Orange County cities, does not allow occupancy of a recreational vehicle as a permanent dwelling on a private residential lot, and Title 15 zoning does not list THOWs as a permitted use. Some California cities (San Jose, Fresno, Humboldt County, Placer County) have adopted bespoke movable-tiny-house ordinances, but Fullerton has not. Confirm current ADU and tiny-house pathways with the Fullerton Planning Division.