A standalone ADU structure with no shared walls with the main house — the most flexible and most expensive ADU type.
Under the general ADU ordinance rules, a city cannot set a maximum ADU size below 850 sqft, or 1,000 sqft for more than one bedroom; separately, no local lot-coverage, floor-area, open-space, front-setback or minimum-lot-size rule can block an ADU with at least 800 sqft of interior livable space and four-foot side and rear setbacks. 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.