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 under California state ADU law — 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.
Quick answers
Which Orange County cities have pre-approved ADU plans?
Do ADU rules really differ city by city?
Which city is fastest for an ADU permit?
Use this table to find your city, then go deeper. California ADU law explains the state floor every city on this list has to respect, the Orange County permit guide covers what a submittal actually contains, and the timeline guide converts the review clocks into calendar time. If a city column here surprises you, the state law page usually explains why the city cannot go further than it does.