California · CA
ADU laws & builders in California
California leads the country on ADU legalization. State law SB-9 and SB-1211 require cities to allow ADUs on most single-family lots and limit owner-occupancy restrictions. Many cities run their own pre-approved plan programs that compress the permit timeline from months to weeks.
Last reviewed: 2026-05-29
Are ADUs legal in California?
Yes. California has the most ADU-friendly laws in the country. A series of state bills now require cities to permit at least one ADU and one Junior ADU (JADU) on most single-family lots, cap how much cities can restrict them, and force faster permit review. SB-9 opened lot splits and duplex conversions on many single-family parcels, and SB-1211 (effective 2025) further expanded how many detached ADUs are allowed on multifamily properties. The practical result: if you own a typical California home, you can almost certainly build an ADU.
Key rules that affect your build
Cities must approve or deny a complete ADU application within 60 days. Owner-occupancy requirements are limited for many ADUs. There are statewide size allowances (commonly up to 800–1,200 sq ft depending on configuration) that cities cannot zone below, and reduced or waived parking requirements near transit. Impact fees are limited or waived for smaller units. Exact setbacks, height, and design standards still vary city to city — which is why a builder who knows your specific city's rules matters.
Cost and timeline in California
A permitted, turnkey detached ADU in California typically runs $200K–$450K depending on size, finishes, and site conditions; garage conversions and JADUs can come in lower. From signed contract to final sign-off, plan on roughly 8–14 months. Choosing one of the city pre-approved plans below can cut the permit phase from months to weeks and save $15K–$25K in design fees.
Official source
We summarize California's ADU rules in plain English. For the authoritative, always-current legal detail, go straight to the source:
California HCD — Accessory Dwelling UnitsAlways verify current rules with the official source before making decisions.
Pre-approved ADU plan programs in California
- Los Angeles — LA Standard Plan Program
- San Jose — San Jose Pre-Approved ADU Program
- San Diego — Permit-Ready ADU Program (PRADU)
- Sacramento — Permit-Ready ADU
- Oakland — Pre-Approved ADU
Find a verified ADU builder in California
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