ADU Permit and Approval Process in California

This page is general homeowner education, not legal advice. Requirements vary by city and county — always confirm current rules with your local building department.

The statewide framework

California Government Code §65852.2 is the state law that governs ADU permitting statewide. It requires cities and counties to allow ADUs on most residential lots, sets limits on how restrictive local agencies can be (for example, around minimum lot size requirements and parking mandates in many cases), and requires a ministerial (staff-level, non-discretionary) review process for qualifying ADUs rather than a lengthy public hearing. The intent of the law is to make ADU approval faster and more predictable statewide than it was previously.

Local agencies still administer the process

Even with a statewide framework, your actual permit application goes through your city or county's building department, and local agencies can still apply their own zoning overlays, design standards, and review timelines within what state law allows. This is why the process can look different in the Bay Area, San Diego, Sacramento, and Los Angeles even though the same state law applies everywhere — see our regional pages for area-specific notes.

General steps homeowners go through

1. Confirm zoning and eligibility. Most residential lots qualify for at least one ADU, but confirm with your local planning department.
2. Prepare plans. Site plans and construction drawings, typically prepared by an architect, designer, or your contractor's design team.
3. Submit for plan review. Your local building department reviews the application against zoning and building code requirements.
4. Address plan check comments. Most projects receive at least one round of correction comments before approval.
5. Receive your building permit. Construction can begin once the permit is issued.
6. Inspections during construction. Framing, electrical, plumbing, and final inspections happen at defined points in the build.
7. Final approval / certificate of occupancy. The unit becomes legally occupiable once final inspection is passed.

Special considerations

Coastal-zone properties may face additional Coastal Commission review in some jurisdictions. Hillside and fire-hazard-zone properties may face additional structural or defensible-space requirements. Historic districts may have design review overlays. A contractor experienced in your specific jurisdiction will already know which of these apply to your property.

Why the contractor you choose matters here

A licensed contractor who regularly works in your city or county has usually been through this exact process repeatedly and knows the local department's expectations. That experience often matters as much as construction skill in keeping a project on schedule.