How do pre-approved ADU plans work in California, and are they faster?

Every California city and county must run a program that pre-approves ADU plans, and when you apply for a detached ADU using a qualifying pre-approved plan, the agency must approve or deny your complete application within 30 days instead of the usual 60. A pre-approved plan speeds up review of the building design, but you still need a permit and site-specific documents for your lot.

What the law requires

AB 1332 (2023) added Government Code section 65852.27. Under it, each local agency had to set up an ADU plan pre-approval program by January 1, 2025. The agency:

• must accept plan submissions for pre-approval and cannot restrict who submits them;
• reviews those plans against the state ADU standards and may charge the same permit fees it would charge for an ADU of the same size;
• must post pre-approved plans on its website, with the designer's contact information; and
• may also admit its own plans and plans pre-approved by other agencies in California.

Posting a plan is not an endorsement of the designer and does not approve your project.

When the 30-day clock applies

The 30-day decision applies to a detached ADU application that uses either a plan the agency pre-approved within the current triennial California Building Standards Code cycle, or a plan identical to one used in a detached ADU application the agency approved during that cycle. The building code is updated every three years, so a plan approved under an earlier cycle may not qualify. Ask whether the plan has been updated to the current code before you buy it.

How local programs look in practice

Programs differ. Los Angeles County runs a County Catalog of plans that are free to the public plus a Private Designer Catalog, both pre-approved by Regional Planning and Public Works Building and Safety. The City of Los Angeles runs a Standard Plan Program; LADBS says the plans are privately owned and bought from the plan owner, that owning a standard plan does not waive the building permit, that you submit plans showing how the design is adapted to your site, and that soil or site conditions may require changes.

What this means for your MEP plans and permit set

A pre-approved plan is a building design, not a site design. Your lot still determines where the sewer line runs and how it ties into your existing lateral, whether your existing electrical service can carry the new load, how the subpanel feeder is routed, how water service reaches the unit, and whether the plan's energy compliance covers your climate zone and the unit's orientation. Before you commit, ask the plan owner exactly which mechanical, electrical, plumbing and Title 24 documents come with the plan, and plan to fill the gaps with site-specific sheets so you keep the speed advantage you chose the plan for. See how the Los Angeles ADU process works, why load calculations matter, and the California ADU permit guide. Program details vary by city and county, so confirm them with your planning or building department.

Sources: leginfo.legislature.ca.gov, hcd.ca.gov, planning.lacounty.gov, dbs.lacity.gov.