Twain Harte, CA Accessory Structures: Tiny Homes (2026)

Unincorporated Tuolumne County regulates tiny homes through its existing Title 17 (Zoning) framework and the building code rather than a dedicated tiny-home chapter. How a tiny home is treated depends on its construction. A tiny house built on a permanent foundation is reviewed as a single-family dwelling or, more commonly, as an Accessory Dwelling Unit under the County's Title 17 ADU chapter; that pathway carries the state ADU minimums (an ADU of at least 800 square feet is allowed, the minimum floor area can be as small as 150 square feet, and detached new-construction units may reach 16 feet) and ministerial approval. The County's Building and Safety Division has also offered pre-approved plan programs for ADUs and single-family dwellings, which can streamline a small home. A tiny house on wheels (built on a chassis) is generally treated as a movable structure similar to a recreational vehicle or, if HUD-certified, a manufactured home, and may only be placed where such units are permitted (for example certain agricultural parcels or licensed parks) rather than as a permanent residence on any lot. Manufactured homes are not currently required to have fire sprinklers in the County. Because most of unincorporated Tuolumne County sits in fire-hazard terrain, defensible-space and building-code fire provisions apply to any inhabited structure. Anyone planning a tiny home should confirm with the Community Development Department whether it will be permitted as an ADU, a dwelling, or a movable unit, because that classification determines the applicable standards.