As of October 2026, San Diego builders publish total timelines from about 6 to 12 months at the quick end to 10 to 18 months or more at the slow end, design through move-in. Garage conversions tend to be faster. State law caps city review at 60 days after a complete application; the rest is design, corrections and construction.
What are the phases?
| Phase | Published San Diego estimates, as of October 2026 | What sets the pace |
|---|---|---|
| Feasibility and design | About 1 to 5 months | How quickly layout and finish decisions are made |
| Permitting | A few months; one builder estimates about 3 to 9 | Completeness of the first submittal and the number of correction rounds |
| Construction | About 5 to 10 months | Size, one or two stories, foundation and site work, inspection scheduling |
Ranges come from Maxable (July 2026) and SnapADU (November 2025, updated August 2026). They are third-party estimates and do not describe our schedule.
What does state law say about review time?
As of October 2026, the permitting agency has 15 business days to confirm an ADU application is complete and 60 days from a complete application to approve or deny it, when a home already exists on the lot. Since 2026 that 60-day period applies in the coastal zone too. Each correction round sends plans back to the designer, so a well-prepared first submittal saves the most time.
What tends to slow San Diego projects down?
- Coastal review. Maxable estimates that a Coastal Development Permit, when needed, adds 2 to 4 months.
- Correction rounds. Maxable notes plan sets often go through three or four review cycles.
- Sloped or canyon lots that need soils reports, engineered foundations or retaining walls.
- Utility work, especially new electrical service or a long sewer run.
- Late design changes after the permit is issued, which can require a revision.
Is a garage conversion faster?
Often, because the shell already exists and there is no new foundation or roof to build. Structural surprises in an older garage can still add weeks, so we open up and inspect the critical areas early.
Does a ready-made plan speed things up?
It can shorten design. As of October 2026, the City of San Diego accepts San Diego County's Standard ADU Building Plans and Encinitas's Permit Ready ADU plans. Site-specific items such as the site plan, foundation and utilities still go through review.
Sources, as of October 2026:
- Maxable, "How to Build an ADU in San Diego" (July 2026).
- SnapADU, "How Long Does it Take to Build an ADU?" (November 2025; updated August 2026).
- California Department of Housing and Community Development (HCD), ADU Handbook, updated March 2026, with its addendum on law in effect January 1, 2026, hcd.ca.gov.
- City of San Diego Planning Department, Housing Toolkit: Accessory Dwelling Units page, sandiego.gov.