An ADU permit in California is faster, cheaper, and more predictable than any other residential permit type. State law requires ministerial review — meaning no discretionary hearings — and a 60-day decision window once your application is complete. But "60 days" only counts after the city accepts your submittal. Getting to that point is where most projects stall.
This guide walks through the full permit timeline, explains what each phase actually checks, and notes how the largest California jurisdictions differ in practice.
The Five Permit Phases
- Pre-application. Optional in most cities, mandatory in some (San Francisco, Los Angeles for hillside lots). The city reviews zoning compliance and flags missing items before formal submittal.
- Submittal and intake. You submit the full plan set (architectural, structural, MEP, Title 24, soils report when required). Intake clerk checks for completeness only — not technical correctness. Returns within 1–5 business days.
- Plan check. Building, planning, fire, and public works each review their slice. Building plan check is typically the longest. State law caps the first round at 60 days for ADUs.
- Corrections. Plan checkers issue comments. Your designer addresses each one and resubmits. Each subsequent round must complete within 60 days. Most ADUs require 1–2 correction rounds.
- Issuance. Once all comments are cleared, fees are paid and the permit is issued. Construction can begin.
Realistic Timeline (Permit Phase Only)
From "complete application submitted" to "permit issued":
| Scenario | Typical Duration |
|---|---|
| Best case (clean plans, simple lot, fast jurisdiction) | 6–10 weeks |
| Typical (1 correction round) | 3–4 months |
| Slow (2+ rounds, complex lot, slow jurisdiction) | 5–7 months |
What Plan Checkers Actually Look For
- Setbacks, height, and footprint match the zoning district
- Structural calculations cover gravity and lateral loads (CBC + ASCE 7)
- Foundation matches geotechnical recommendations
- Energy compliance per Title 24 (CFR-1R-NCB form attached)
- Egress windows and doors per CRC R310
- Smoke and CO alarms shown on plans per CRC R314/R315
- Accessibility (where applicable) per CBC Chapter 11A
- Fire separation from existing structures and lot lines per CRC R302
- Utility plans show connections, demand, and panel upgrades if needed
County and City Differences
State law is uniform but local administration varies. Notable differences in 2026:
Los Angeles (City)
Largest ADU volume in the state. EXPRESS-ADU pre-approved plan program lets you skip plan check entirely if you use one of their stock plans. Plan check otherwise runs 8–14 weeks. Hillside lots require additional grading and slope reports.
San Diego (City)
Pre-approved ADU plan program with about 30 stock designs. Online submittal portal. Median plan check 6–10 weeks. Coastal Zone parcels require coastal permit on top of building permit (separate timeline).
San Francisco
Pre-application meeting required. Plan check 12–20 weeks because of additional reviews (Historic Preservation, MTA driveway review, Public Works ramp/curb cut review). Owner-occupancy not required for ADUs but JADUs follow city ordinance.
San Jose / Santa Clara County
Generally faster than SF. Plan check 4–8 weeks for clean submittals. Pre-approved plan program available. Fire-zone lots in the foothills add wildland-urban-interface fire requirements.
Sacramento
Streamlined ADU permit pathway with online submittal. Plan check 4–6 weeks typical. Most parcels qualify for ministerial review without setback variances.
Oakland / Berkeley
Berkeley requires soils report for any new foundation. Oakland enforces strict tree protection ordinance — survey required if any protected tree is within 50 ft of construction. Plan check 8–12 weeks.
Unincorporated County (varies)
Often faster than city jurisdictions because of lighter staff load, but utility connection can be more complex (well, septic, propane). Plan check 3–8 weeks; field inspections sometimes the bottleneck.
Three Things That Cause Most ADU Permit Delays
- Incomplete soils report. If you skip the geotechnical investigation, plan check will return the entire submittal until you provide one. Two weeks lost.
- Setback miscount. Owners measure from the wrong reference (e.g., property pin vs. fence line). Use a recent survey or an ALTA — not a guess.
- Title 24 form not signed. The energy form must be wet-signed by a CEA or CABEC-certified energy analyst. Trivial-looking but blocks issuance.
Permit Support from XE Engineering
Every XE plan includes the structural calculations, framing details, and connection details that plan checkers require. For an additional flat fee, our Permit Support add-on lets you forward the city's correction comments to our engineers; we respond within 5 business days. This typically cuts the correction phase from 6 weeks to 2.
For custom sites or jurisdictions with unusual requirements, our structural engineering services include scoped permit-support hours from day one. Contact us with your jurisdiction and lot details for a fixed-fee proposal.