Building an accessory dwelling unit (ADU) in Los Angeles is much more predictable than it was a few years ago. State law has made ADUs a ministerial approval. That means if your plans meet the objective standards, the city reviews them against a checklist and doesn't hold a discretionary hearing. The process still has several steps, though, and most delays come from skipping one of them. This guide covers how the ADU permit process works in the City of Los Angeles, from the first zoning check to the final inspection.
Step 1: Decide what kind of ADU you're building
The type of unit affects which rules apply and how complex the plans will be:
- Detached ADU: a new, freestanding building, usually in the backyard.
- Attached ADU: an addition connected to the main house.
- Garage conversion: turning an existing garage into living space. It's often the most direct path because the structure is already there.
- Junior ADU (JADU): a smaller unit created inside the existing home, with its own rules, including an owner-occupancy rule.
If you're comparing options, our ADU and garage conversion page explains what each one involves on a typical LA lot.
Step 2: Check your lot before you design
Before anyone draws plans, look up your property's zoning and overlays. The City of Los Angeles publishes parcel information through ZIMAS, its online zoning map. Things to look for:
- Zone and lot size: these set the basic rules for setbacks and height.
- Hillside areas: these can bring extra grading, access and foundation requirements.
- Very High Fire Hazard Severity Zones: these affect fire access, materials and sometimes parking rules.
- Coastal Zone: lots here may need a coastal review on top of the building permit.
- Historic Preservation Overlay Zones (HPOZ): these can add design review for anything visible from the street.
Also check where the sewer line, gas meter and electrical service are. An older electrical panel often has to be upgraded to carry a second unit, and planning that early saves a redesign later.
Step 3: Choose custom plans or a standard plan
You have two main routes:
Custom plans. A designer or architect draws an ADU for your lot. You get the most flexibility, and the plans go through full plan check.
The LADBS ADU Standard Plan Program. LADBS keeps a gallery of ADU plans that have already been reviewed for the Building, Residential and Green Building codes. Choosing one can shorten plan check, because the building code review is already done. You still need a site-specific review for zoning and the foundation, and a site plan showing where the unit goes on your lot. The city also offers its own free standard plan for a small one-bedroom unit, so check the program page for current options.
Either way, the drawings need a site plan, floor plans, elevations, structural details, and energy compliance documents (Title 24).
Step 4: Submit to LADBS for plan check
In the City of Los Angeles, ADU plans are generally submitted electronically through ePlan LA. Plan check reviews the project against zoning, building, fire, and green building requirements. Depending on the lot, other departments may also need to clear the plans, for example fire access, sanitation or sewer capacity, or utility service.
How long does the city have?
California Government Code Section 66317 sets the clock. The permitting agency has to determine whether the application is complete within 15 business days. Once it's complete, and there's an existing home on the lot, the agency has 60 days to approve or deny it. If it doesn't act in time, the application is deemed approved. The clock pauses while the agency is waiting on you. That's why the quality of the first submittal matters so much: every round of corrections adds time on your side of the process.
Step 5: Respond to corrections
It's normal to get a correction list after the first review. Common items include missing dimensions on the site plan, unclear setback measurements, structural calculations, fire sprinkler or fire access questions, and energy calculations. A clear, complete response sheet that answers each item helps the next review go faster. This is where an experienced contractor and designer working together save time, because many corrections are about how the unit will actually be built.
Step 6: Pay fees and pull the permit
Once plans are approved, the permit is issued after fees are paid. Fees depend on the size of the unit and the services it connects to. Some state rules limit impact fees on smaller ADUs. Ask for a fee estimate during plan check so there are no surprises, and confirm whether utility upgrades will need separate applications.
Step 7: Build and pass inspections
With the permit issued, construction can start. The building inspector visits at key stages, typically:
- Foundation, before the concrete is poured
- Framing, plus rough plumbing, electrical and mechanical
- Insulation
- Drywall, where required
- Final inspection, after which the unit can be used
Each stage has to pass before the work is covered up, so the schedule depends partly on inspection availability. A good contractor books inspections ahead and keeps the job ready for them.
Common mistakes that slow ADU permits in LA
- Designing before checking the lot. Easements, overhead power lines, protected trees or a hillside designation can force a redesign.
- Ignoring utilities. Panel upgrades and sewer connections often take longer than expected.
- Incomplete first submittals. Every resubmittal adds weeks.
- Changing the design mid-review. Even small changes can restart part of the review.
Working with a contractor on your ADU permit
RD Fast Construction Inc. is a California Class B general contractor (Lic. #1105076), licensed since 2023. Owner Rafael Diaz has more than 10 years in construction. We build detached ADUs, garage conversions and JADUs across the City of Los Angeles and nearby LA County cities, and we handle permit coordination and inspections as part of the job. If you're not sure which ADU type fits your lot, call or text us and we'll walk the property with you.