One of the first questions families ask when they start thinking about a backyard home is how long it’s going to take. The honest answer for most projects in San Diego County: somewhere between six months and twelve months from start to a finished, livable unit. Simpler conversions can move faster. Complex builds on challenging sites can run longer. Understanding how long to build an adu, phase by phase, helps you plan around the process instead of being surprised by it.
Here’s what a realistic timeline looks like.
Phase 1: Design (6 to 10 Weeks)
Design is where the project takes shape on paper. At ADUz, we start with a feasibility review before anything gets drawn. That step confirms what your lot will actually allow in terms of setbacks, utilities, and size, and it usually takes one to two weeks.
From there, the design phase includes schematic drawings and layout development, structural engineering if required (typically required for detached new builds), Title 24 energy compliance documentation, and any specialty reports your jurisdiction requires. Geotechnical reports for sloped lots are the most common example.
For straightforward projects, design moves quickly. A garage conversion with a simple layout and no structural complications can be ready for permit submission in six weeks. A new detached build with a custom layout may take closer to ten or twelve weeks, depending on engineering timelines.
What Slows Design Down
The biggest culprit is layout changes mid-process. Every round of revisions adds time. The clearer you are about what you want going into the design phase, the faster it moves. Coming to the first meeting with decisions made on bedroom count, bathroom configuration, and any must-haves shortens this phase considerably.
Phase 2: Permits (6 to 16 Weeks)
This is the phase most people underestimate, and the one ADUz has spent the most time learning how to navigate efficiently.
Permit timelines vary by jurisdiction. Here’s a general picture of what to expect across San Diego County:
City of San Diego: Over-the-counter review is available for certain ADU types and can result in same-day or next-day approval. More complex projects go through standard review, which currently runs eight to twelve weeks.
Other incorporated cities (Oceanside, Vista, Escondido, Chula Vista, and others): Review times vary. Some cities have improved their turnaround; others are still working through backlogs. Six to fourteen weeks is a reasonable range.
Unincorporated San Diego County: The county permit office has its own process and current review times. These shift, and we track them actively.
California law requires jurisdictions to approve or deny ADU permits within 60 days of a complete application. Getting to a complete application usually involves some back-and-forth, but that 60-day clock is real protection once you’re there.
The permit phase is where projects sit the longest. Working with a team that knows what each jurisdiction wants in the permit package and submits a complete set the first time is the single biggest factor in shortening this phase.
What Slows Permits Down
Incomplete submittals. If a permit package is missing documents, it gets sent back. The correction cycle can add weeks to the review clock. ADUz prepares complete permit packages because we’ve seen what incomplete submittals cost in time.
What You Can Do While Permits Are In Review
The permit phase doesn’t have to be dead time. Once the application is submitted, there are productive things to work on.
Finish selections are the most valuable. Flooring, fixtures, appliances, cabinets, and paint all take time to source and order. Getting these decisions made during permit review means materials can be ordered before approval comes through, which can shave weeks off the construction start.
Some utility pre-work can also be coordinated with the local utility provider before the permit is in hand. Your project team can flag which connections are worth getting on the schedule early.
Phase 3: Construction (3 to 7 Months)
Once permits are approved, construction can begin. This is handled by our licensed build partner, The Rock Remodel (CA Lic. 1042918).
Timeline depends heavily on the type of ADU.
Garage conversion: Three to four months is typical for a well-organized conversion. The structure is already there, so work focuses on insulation, drywall, interior framing, plumbing, electrical, and finishes.
Detached new build: Four to seven months for most projects. Foundation work, framing, roofing, rough mechanical, insulation, drywall, finishes, and utility connections take time when you’re starting from scratch.
Junior ADU inside the existing home: Often the fastest option. Two to three months for interior work that doesn’t require major structural changes.
What Slows Construction Down
Material lead times are the most common culprit, especially for windows, doors, and specialty fixtures. Subcontractor scheduling during busy periods adds time. Inspection scheduling is another factor because each phase of construction has to pass inspection before the next phase can begin.
Working with a coordinated design-build team where the designer and contractor are already aligned means inspections get scheduled at the right time, materials are ordered before they’re needed, and the project doesn’t pause while people figure out what happens next.
Realistic Totals for San Diego County ADU Projects
For most projects in San Diego County:
- Simple garage conversion: 6 to 9 months total
- Detached new build on a straightforward lot: 9 to 12 months total
- Complex builds with sloped sites, structural complications, or coastal review: 12 to 18 months
These ranges assume a reasonably smooth permit process. Jurisdictional delays, site surprises, or significant design revisions can extend any project. A proper feasibility review and a coordinated team reduce those variables significantly.
How ADUz Keeps Your Project Moving
ADUz is a family-owned company in San Diego County. Alma leads design and permitting. Her husband David leads construction through The Rock Remodel. Because design and construction are coordinated from day one, the permit package is built the way the contractor actually needs it, inspections happen on schedule, and no one is waiting on a decision that should have been made three weeks earlier.
We’re bilingual and we’ve guided families through ADU projects across the county. We know what Escondido wants in a permit package and what Chula Vista’s process looks like right now. We designed ADUz for the way your family grows, and part of that is being honest about timelines so you can plan around them.
If you want to understand what a realistic schedule looks like for your project, the next step is a conversation. Call ADUz at (760) 524-1754 for a free ADU consultation. We’ll give you a straight answer about your lot, your timeline, and what to expect along the way. Family owned, bilingual, and here when you’re ready.