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How long does an ADU take to build in Los Angeles?
From the first design meeting to final inspection, an ADU in Los Angeles typically takes about 8 to 14 months. Design and engineering usually take 1 to 3 months, permit review up to 60 days for a complete application under state law (longer if corrections are needed), and construction roughly 4 to 6 months for a garage conversion or compact detached unit and 6 to 8 months for a larger or hillside unit.
| Total, design to final | About 8 – 14 months |
|---|---|
| Design and engineering | 1 – 3 months |
| Permit review | Up to 60 days per complete application (2 – 4 months with corrections) |
| Construction | 4 – 8 months depending on type and site |
The three phases
Design and engineering, 1 to 3 months. Site survey, feasibility against setbacks and height limits, floor plan, structural engineering, Title 24 energy compliance and utility planning. Pre-approved standard plans can shorten this phase.
Permits, up to 60 days once complete. State law gives the city 60 days to approve or deny a complete ADU application. The clock starts when the application is deemed complete, so the realistic permit phase is often 2 to 4 months once correction cycles are counted.
Construction, 4 to 8 months. Garage conversions and compact detached units sit at the low end; new detached units with foundations, long utility runs, hillside conditions or high-end finishes sit at the high end. Inspections at foundation, framing, rough mechanical, insulation, drywall and final add fixed points to the schedule.
What actually causes delays
Incomplete submittals, utility upgrades that need the power company's involvement, long-lead items such as windows and cabinets ordered late, and changes after construction starts. Ordering long-lead materials when the permit is issued, not when the slab is poured, is the single biggest schedule protection. Oria Builders (CSLB #1029255) runs ADU projects on a written schedule with milestones tied to inspections; confirm current review times with LADBS for your neighborhood.
Related Questions
Is a garage conversion faster than a detached ADU?
Usually. The structure exists, so construction is often 4 to 5 months instead of 6 to 8, and there is no new foundation to inspect.
Can a prefab ADU cut the timeline?
Factory-built units shorten on-site construction, but the site work, foundation, utilities and permits still take their normal time, so total savings are often a few months, not more.
Do I need to be home during ADU construction?
No. Most ADU work is confined to the yard or garage, and homeowners usually stay in the main house throughout.
Sources
Related
- General contractor in Los Angeles
- ADU Construction
- Project: Full Remodeling and garage conversion to an ADU in Los Angeles – Precision Punch List Completion
- Case study: Modern ADU Creation in Santa Monica’s Ocean Park Neighborhood
- Can I convert my garage into an ADU in Los Angeles?
- What does a general contractor charge in Los Angeles?
- How much does a 400-square-foot ADU cost?
Answered by Gilad Segev — Founder & Licensed General Contractor, Oria Builders (CSLB #1029255). Last updated October 2, 2026.