Modesto, CA Accessory Structures: Tiny Homes (2026)

A tiny home that meets the California Building Standards Code or HUD Manufactured Home standards and is placed on a permanent foundation can be permitted as an Accessory Dwelling Unit under Modesto Municipal Code section 10-4.115. The ordinance follows the ministerial review framework set by California Government Code section 65852.2: a detached new-construction ADU may be up to 800 square feet, with a maximum height of 16 feet for a one-story detached unit (or up to 25 feet, or two stories, when attached to the primary dwelling, subject to the underlying zone). Side and rear setbacks are a minimum of 4 feet, and parking can be required at up to one space per bedroom but is waived where the property is within one-half mile of a transit stop or otherwise exempt under state law. A Junior ADU (JADU) of up to 500 square feet is permitted within the walls of an existing or proposed single-family home if the property is owner-occupied. Tiny homes on wheels (THOWs), park-model RVs, and recreational vehicles are not treated as ADUs under state or city ADU law because they are not built to the California Residential Code and lack a permanent foundation; living in an RV outside of a permitted park is not a permitted use. Modesto also runs an ADU Express Program offering same-day plan review for ministerial projects. Stanislaus County partners with Modesto on a free pre-approved ADU plan library.