How to Get an ADU Permit in Southern California: Step-by-Step (2026)

Permitting is the part of an ADU project that scares homeowners most — and it’s the part most builders are worst at explaining. Here’s the complete step-by-step process for Southern California, county by county, with the official portals and real timelines.

The 7 Steps to an ADU Permit (Everywhere in California)

1. Feasibility & zoning check — confirm lot eligibility, zoning, setbacks, easements, and overlays (fire, coastal, flood) before spending money on design.
2. Design & plan preparation — architectural and structural plans, site plan, Title 24 energy documentation, calculations.
3. Submit the permit application — file through your city or county’s online portal with forms, valuation, and plan-check fees.
4. Plan check & corrections — building, planning, fire, and public-works reviewers issue comments; you revise until everyone signs off.
5. Permit issuance — pay remaining fees and receive stamped plans plus the building permit card authorizing construction.
6. Construction inspections — schedule required inspections at each phase: foundation, framing, electrical/plumbing/mechanical rough-in, and more.
7. Final inspection & occupancy — final sign-off, Certificate of Occupancy, and any required deed restrictions recorded.

Key timing rule: state law (SB 543, effective 2026) requires ministerial ADU review within 60 days — but the clock only starts once your application is deemed complete. Incomplete submittals reset it. Getting the submittal right the first time is the single biggest schedule saver.

Los Angeles County

Portal: EPIC-LA — the county’s online permitting system for unincorporated areas. The county’s official five steps: Application → Plan Check → Permit → Inspection → Completion. Zoning review runs through Regional Planning first, then Public Works Building & Safety handles plan check.

• Pre-approved plans: yes — the county’s Pre-Approved ADU Standard Plans Program offers three county-owned plans free to use.
• Expedited review: yes — an official Expedited ADU Plancheck track exists via EPIC-LA (plans uploaded as one combined PDF).
• City of Los Angeles (LADBS): separate system at dbs.lacity.gov — the city also runs its own approved standard plans program (a free LADBS sign-in is required to browse the catalogue).

Orange County

Portal: MyOCeServices (OC Development Services / OC Public Works) for unincorporated areas. Your plan checker acts as project manager through all clearances; inspections are scheduled online, and a Certificate of Use & Occupancy is issued after final inspections.

• Timeline: the county publishes real numbers — typical first plan-check turnaround is 15 business days, rechecks 10 business days.
• Pre-approved plans: yes — OC Development Services offers a pre-approved ADU plan program; structural and energy review is pre-done, so only site-specific review remains.

Riverside County

Portal: PLUS Online — apply online, upload a single multi-page PDF of plans plus the permit application; submittals are processed for intake within about 3 business days with parallel plan review.

• Pre-approved plans: yes — the county’s “Permit Ready ADU” program offers three free plans: a 499 sq ft studio, a 625 sq ft 1-bed/1-bath, and a 749 sq ft 2-bed/1-bath.
• City of Riverside: Building & Safety at riversideca.gov — first plan-check review runs about 10 business days, subsequent reviews about 5.

San Bernardino County

Portal: EZOP (EZ Online Permitting) — register, select Planning/Fire/Building/Enforcement/Public Works, submit and pay fees online; approval and correction notices arrive by email.

• Timeline: the county must approve or deny an ADU application within 60 days of receiving a complete application (per the county’s official ADU handout).
• Fee break: zero transportation impact fees for ADUs under 750 sq ft.
• Watch out: septic lots may require a percolation report — check this during feasibility, not after design.

How Pre-Approved Plans Speed Things Up

Using a pre-approved plan skips structural and energy re-review — but never skips site-specific zoning and foundation review. That’s why our Cities with Pre-Approved Plans guide pairs with this page: pick your city’s plan, and we handle the site work and submittal.

Portals, timelines, and programs change; verify current requirements with your city or county building department before submitting. This page is general information, not legal advice.