A standalone ADU structure with no shared walls with the main house — the most flexible and most expensive ADU type.
California state law guarantees a minimum allowance of 850 sqft (studio/1BR) or 1,000 sqft (2+BR) for detached ADUs on any single-family lot. Many cities allow up to 1,200 sqft. Typical 2026 all-in cost: $135k-$360k in LA, higher in Bay Area.
Part of the BackyardADU California ADU Glossary — plain-English definitions of the regulatory, construction, and financing terms you'll encounter during a California ADU project.