Once homeowners get past what an ADU will cost, the next question is almost always how long it will take.
The honest answer is that the timeline has gotten better. California passed a wave of laws over the last two years
specifically to speed up ADU approvals, and several of the most useful changes took effect in 2026. Here is a realistic
breakdown of how long an ADU takes in Los Angeles today, and where projects tend to get stuck.
(If you haven’t nailed down budget yet, start with our companion piece: How Much Does an ADU Cost in Los Angeles in
2026?)
The short answer
For a typical detached ADU in Los Angeles, a realistic timeline from your first design conversation to move in usually lands somewhere around 8 to 14 months. Garage conversions can be faster. Complex or hillside sites can run longer.
That range breaks into four phases: design, permitting, construction, and final sign off.
Phase 1: Design and planning (about 1 to 3 months)
This is where you decide what you’re building: the size, the layout, where it sits on the lot, and how it connects to utilities. Your designer or architect produces the plans everything else depends on.
How long this takes depends mostly on you. Homeowners who know what they want move through design quickly. Homeowners who revise repeatedly stretch it out. The plans also have to reflect your site’s real conditions, including setbacks, lot layout, existing structures, and utility locations, so a little diligence here prevents problems later.
Speed tip: as of 2026, every California jurisdiction must keep a set of preapproved ADU plans available. Choosing a preapproved design instead of a fully custom one can shorten both the design and the permit phase, because the design has already been reviewed. It isn’t right for every lot, but it’s worth asking about.
Phase 2: Permitting (faster than it used to be)
Permitting used to be the black hole of ADU projects. Applications would disappear into plan check for months with no clear deadline. That is the exact problem the newest laws were written to fix.
Here is what changed and what it means for your timeline.
The completeness clock. Under a 2026 state law, once you submit your application, the city has 15 business days to tell you whether it’s complete. If they miss that deadline, the application is automatically deemed complete. This ends the old game of open ended, drip fed correction lists.
The approval deadline. For a complete application, cities must approve or deny within 60 days. Combined with the completeness clock, that puts real, enforceable limits on how long the city can take.
Preapproved plans move even faster. When you use a preapproved plan, cities are generally held to an even shorter review, and in practice LADBS has reportedly issued permits on preapproved plans in as little as a few weeks.
Private plan check as a backstop. State law also lets homeowners bring in a certified private professional for plan review if a city can’t finish in time, another pressure valve on delays.
The practical result: for a complete, well prepared application, permitting in LA is now often measured in a few months rather than the open ended waits of a few years ago. The key phrase is complete and well prepared, which is entirely within your control when you work with a team that knows what the city wants.
Phase 3: Construction (about 4 to 8 months)
Once you’re permitted, construction is the most predictable phase, because your builder controls it directly.
For most detached ADUs, active construction runs somewhere around 4 to 8 months, depending on size, complexity, finishes, and site conditions. A straightforward garage conversion sits at the shorter end. A larger detached unit, a hillside lot, or a site that needs significant utility or foundation work sits at the longer end.
The big timeline drivers are the ones you would expect. Site conditions matter, since a flat, accessible backyard builds faster than a sloped or difficult one. Utility upgrades matter, since older homes often need an electrical panel upgrade and new sewer, water, or gas connections to support a second dwelling. And finish selections matter, since indecision or long lead custom materials can stall an otherwise smooth build.
Phase 4: Final inspections and utilities (a few weeks)
At the end, the ADU goes through final inspections, and utility connections and meters get finalized before you receive your certificate of occupancy and can legally move in or rent.
This phase is usually short, but it’s worth knowing it exists. Many homeowners mentally finish at the last coat of paint and forget there is a sign off step after it.
What actually causes delays
In our experience, ADU projects rarely get delayed by construction itself. They get delayed by the things around it: incomplete permit applications that bounce back for corrections, utility coordination (especially panel upgrades and new service connections), site surprises on older or sloped lots, design changes made after permitting that send you back through review, and decision lag on finishes, fixtures, and layout.
Almost all of these are avoidable with planning. The new laws fixed the city side delays. The remaining delays are mostly about preparation.
How to move faster
Consider a preapproved plan, since it can compress both design and permitting. Submit a genuinely complete application, because the 15 day clock and 60 day deadline only help you when your submittal is clean. Handle utilities early, so you know whether you need a panel upgrade or new connections before construction, not during. Make your finish selections up front, so the build doesn’t wait on decisions. And work with a team that knows LA, because local experience with the city’s process is the single biggest lever on your timeline.
Build it right, not just fast
A faster permit is great, but the goal is still an ADU that’s built properly and passes inspection the first time. The 2026 changes sped up approvals. They did not lower the construction and safety standards your unit has to meet. That part still comes down to who is building it.
We have built in Los Angeles since 1989, and being led by a former LA Construction Inspector means we plan projects around what the city actually requires, which is what keeps a timeline predictable.
If you’re thinking about an ADU and want a realistic timeline for your property, book a consultation or call (213) 948-5297. We’ll walk you through the schedule, the permitting path, and what your lot will actually take.
Alloy Builders. Building with precision since 1989. A family business. License #569174. Los Angeles ADUs, custom homes, hillside builds, and multifamily construction.
Note: ADU laws and city timelines are changing quickly and vary by jurisdiction and project. Treat the ranges above as realistic planning estimates, and confirm current rules and processing times with your local building department for your specific property.
