Los Angeles ADU Permit Guide for Homeowners

California state ADU law

SB 9 and AB 2221 streamline ADU approval statewide. Cities cannot deny a permitted ADU on most single-family lots, and most reviews are ministerial — meaning if your plans meet code, they must be approved.

The LADBS process

Submit a complete plan set to LADBS, pay plan-check fees, address corrections, then receive your permit. Most projects take 60–120 days from submittal to approval.

Common pitfalls

Setback violations, fire-sprinkler triggers from existing-home modifications, and utility upgrade requirements (panel size, sewer capacity) are the most common reasons for delays.

The good news is that all three of these pitfalls are knowable before you submit. Setbacks are measurable, sprinkler triggers are determinable from the scope of work, and utility capacity can be checked with the providers. A thorough feasibility review turns surprises into line items.

Step by step: from idea to approved permit

The process starts with feasibility: measuring your lot, locating utilities, and confirming what size and type of unit your property can support. Skipping this step is how homeowners end up paying for plans that cannot be approved.

Next comes design — floor plans, elevations, a site plan, structural engineering, and Title 24 energy documentation. A complete, coordinated plan set is the single biggest factor in a smooth review, because every correction cycle adds weeks.

Then the plans go to LADBS (or your city's building department if you live in one of LA County's independent cities). You pay plan-check fees, the city reviews, and corrections come back if anything needs adjusting. Most projects take 60–120 days from submittal to approval, and well-prepared sets land at the faster end.

One timing note that surprises homeowners: the permit clock and the construction clock are separate. A detached ADU takes 6–9 months from permit submittal to final inspection, and a garage conversion 3–4 months — and the plan-check period is part of that span. Starting the design early is the only way to start construction early.

Documents you will need

A typical ADU submittal includes a site plan showing the lot, existing structures, and the proposed unit; floor plans and elevations; structural calculations; and energy compliance documentation. If your property has any recorded easements or hillside conditions, those get addressed in the plans as well.

A design-build team assembles all of this for you — that coordination is most of what you are hiring. Your job is decisions, not paperwork.

If your project is a garage conversion, the plan set also documents how the existing structure will be brought up to residential standards — insulation, ventilation, and any structural upgrades. If it is new construction, the set includes foundation and framing plans engineered for your lot. Either way, the submittal tells the city a complete story, and complete stories get approved faster.

After approval: the inspections to expect

Once the permit is issued, construction proceeds through a series of city inspections: foundation, framing, rough plumbing and electrical, insulation, and final. Each inspection must pass before the next phase closes up the work.

The final inspection ends with a sign-off and a certificate of occupancy — the document that makes the unit legal to live in or rent out. We schedule and manage every inspection as part of the build.

A note on scheduling: inspections are booked with the city, and each trade phase waits for its sign-off. This is normal and built into the project timeline — a detached ADU runs 6–9 months from submittal to final inspection, and a conversion 3–4 months. Experienced builders sequence the work so inspection waits never leave the site idle.

If your home is in an independent city

Los Angeles County contains 88 incorporated cities, and most of them — Pasadena, Burbank, Long Beach, Santa Monica, and the rest — run their own building departments with their own submittal processes and fee schedules. State ADU law applies everywhere, but the counter you visit and the details of the process depend on your city.

The good news is that the fundamentals are the same everywhere: state law makes ADU approval ministerial on most single-family lots, so a code-compliant plan set must be approved. What changes city to city is the logistics — submittal format, review queues, and local details like design guidelines in some historic districts.

We build across LA County and handle the submittal in whichever jurisdiction your property sits. The process above — feasibility, complete plans, review, corrections, approval — is the same shape everywhere; only the window is different.

Frequently asked questions