A Bay Area ADU typically takes about 9 to 16 months from first design to final inspection — about 12 months on average — roughly 1–2 months for design, 2–5 months for permitting, and 4–8 months for construction. California law (Gov. Code § 66314) requires most cities to approve or deny a complete ADU application within 60 days.
Phase-by-phase timeline
| Phase | Typical duration | What happens |
|---|---|---|
| 1. Feasibility | 1–3 weeks | Confirm lot eligibility, size, setbacks, and budget. |
| 2. Design & engineering | 4–8 weeks | Plans, structural details, and Title 24 energy compliance. |
| 3. Permit submittal & plan check | 2–5 months | City review; 60-day statutory clock on complete applications, plus correction cycles. |
| 4. Construction | 4–8 months | Site work, foundation, framing, systems, finishes, inspections. |
| 5. Final & occupancy | 1–3 weeks | Final inspections, sign-off, utility release, move-in ready. |
Where the delays hide
- Incomplete submittals — the top cause of restarted review clocks.
- Plan-check corrections — each back-and-forth cycle can add weeks.
- Utility & impact-fee coordination — easy to underestimate.
- Trade scheduling gaps — idle time between phases drags the build out.
Active project management compresses this timeline by running design, permitting, and pre-construction in parallel and keeping trades tightly scheduled. See how our managed process works or get a free ADU estimate.
Building in a specific city?
See our local guides for San Francisco, Oakland, Berkeley, Fremont, San Mateo, Palo Alto, and Mountain View.
How long does an ADU take to build?
About 9–16 months end to end: ~1–2 months design, 2–5 months permitting, 4–8 months construction.
Can the timeline be shortened?
Yes — submitting a complete, code-compliant plan set and running permitting in parallel with pre-construction is the most reliable way to save months.
Sources
- California Department of Housing and Community Development (HCD) — Accessory Dwelling Units (state ADU law, including the 60-day approval requirement)
- Your city's planning department portal for local permit, setback, and fee specifics
Timelines are typical ranges observed across Bay Area jurisdictions, compiled by Ground Rise Build for planning purposes; actual durations vary by city, project scope, and review workload.
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