California sets the floor everywhere — ministerial approval, 4-ft side and rear setbacks, and since 2026 a legal review clock (15 days to completeness, 60 days to decide) — but each city runs its own counter, and the differences decide your design path and budget. This table compares 22 Orange County and LA-area cities we build in: who reviews your plans, whether pre-approved plans exist, and the one local factor that matters most. Free to cite with attribution.
We maintain a full guide for every city below — click any city name for the deep dive. This reference table is compiled from each city’s official ADU pages and our own permit-counter experience, and we update it as programs change.
01Orange County cities
| City | Who reviews | Pre-approved plans? | The local factor that matters |
|---|---|---|---|
| Irvine | Own counter | No | The HOA review runs parallel to the city permit — the HOA letter usually sets your start date |
| Santa Ana | Own counter | No | Older housing stock: garage slab condition and panel capacity decide conversion budgets |
| Anaheim | Own counter | No | One of the faster OC plan checks in our experience (~4 weeks on clean submittals) |
| Costa Mesa | Own counter | No | Standard state-law path — the lot, not the counter, decides the project |
| Huntington Beach | Own counter | No | Standard path; wide postwar lots suit detached units |
| Newport Beach | Own counter | No | Slower plan check (10+ weeks is common) — budget the calendar, not just the build |
| Tustin | Own counter | No | Standard state-law path |
| Fullerton | Own counter | No | Standard path; older stock rewards a slab-and-panel check before quoting |
| Garden Grove | Own counter | Yes — ADU Go (active since Jan 2025) | City publishes official ADU handouts in English, Vietnamese and Spanish |
| Orange | Own counter | No | Four historic districts: ADUs there need a preservation professional’s report + design review |
| Mission Viejo | Own counter (administrative, no neighbor notice) | No | HOA architectural review runs in parallel; hillside lots make slope the budget factor |
| Buena Park | Own counter | No | Standard state path, no exotic local wrinkles — the property decides |
| Westminster | Own counter + online submittal portal | Yes — standard plans (pre-approved, not pre-permitted) | City is explicit that full plan check still applies to pre-approved plans |
| Fountain Valley | Own counter | No | Published development-standards handout + famously flat tract lots |
02Los Angeles–area cities
| City | Who reviews | Pre-approved plans? | The local factor that matters |
|---|---|---|---|
| City of LA | LADBS + LA City Planning (LA County if unincorporated) | Yes — LA standard plans | Hillside, coastal and older-home conditions move timelines, not the review clock |
| Long Beach | Own counter | Yes — PAADU catalog (active) | A qualifying catalog design can trim design cost |
| Pasadena | Own counter | Expired (standard plans ended Dec 2025) | Budget for custom design |
| Torrance | Own counter | No | Suburban lots suit detached units and conversions |
| Whittier | Own counter | No | Older homes, generous lots — slab and panel checks first |
| Downey | Own counter + Fire Department review | Program exists, no plans posted yet (as of Jul 2026) | Downey Fire publishes its own ADU fire-plan guide — design to it up front |
| Norwalk | Own counter | No | City publishes a 2026 ADU guidebook + submittal checklist — file it complete and the clock starts |
| Lakewood | Own counter (online portal) | Yes — active AB 1332 program | Two budget lines people miss: school fees (paid at the district) + Construction of Dwelling Unit Tax |
| Cerritos | Own counter | No | Step-by-step published process, posted construction hours — complete submittals matter |
03How to read this table
Three patterns worth noticing:
- Pre-approved plans are spreading — unevenly
Garden Grove, Westminster, Long Beach, Lakewood and the City of LA have working programs; Downey has announced one with nothing posted yet; Pasadena’s expired. Where a program exists, it’s a head start on design — never a skip past plan check or site-specific engineering.
- The second reviewer is the real variable
Irvine and Mission Viejo add an HOA review; Orange adds historic-district review on some addresses; Downey adds a fire review. None of these block a code-compliant ADU — but designing for them from day one is the difference between approval and correction rounds.
- State law is your floor everywhere
Every city on this list must approve a code-compliant ADU ministerially — no hearing, no neighbor veto — on the 15/60-day clock. The city can shape how; it cannot say no.
Compiled from each city’s official ADU resources and L Square’s permit-counter experience across 200+ projects. Reuse permitted with attribution and a link to this page. Corrections welcome: (949) 374-7980.