Placer County allows Tiny Homes which means a second permanent dwelling that is an accessory to a primary dwelling on a site. A secondary dwelling may be either a detached or attached dwelling unit, including a tiny house, which provides complete, independent living facilities for one or more persons. It shall include permanent provisions for living, sleeping, eating, cooking, and sanitation on the same parcel or parcels as the primary dwelling. Secondary dwellings also include multi-generation housing units and are synonymous with accessory dwelling units as defined by California Government Code Section 65852.2. See Section 17.56.200 for specific use requirements applicable to secondary dwellings. ***** “Tiny House” or “Tiny Houses” (land use) means separate, independent living quarters that are no larger than 400 square feet; include basic functional areas that support normal daily routines, including a bathroom, a kitchen, and a sleeping area; is mounted on a wheeled trailer chassis; is designed and built to look like a conventional residential structure, using conventional building materials, and is thus architecturally distinct from traditional mobile homes and recreational vehicles; and is titled and registered to tow legally under the California Department of Motor Vehicles. Includes park trailers as defined in HSC Section 18009.3. (See Section 17.56.350 for specific use requirements applicable to tiny houses).

https://www.placer.ca.gov/DocumentCenter/View/61416/15A