Permit Guide
What it takes to get an ADU permitted in California: how long each stage runs, which state laws apply, and what your specific city requires.
Every ADU needs a building permit, zoning clearance, and Title 24 energy compliance before construction starts. Here's how that plays out, start to finish.
Regular permit
4-6 Months
Pre-approved plan
2-3 Months
A pre-approved plan has already passed city design review: no separate review fee, near-certain approval, and 4-8 weeks faster than a regular permit.
Apex Homes submits your project details and initial documents to the city.
The city reviews drawings against zoning, setbacks, and Title 24 rules.
If comments come back, Apex Homes resolves them and resubmits on your behalf.
Fees are paid and the city issues your official building permit.
City inspectors check the build at each construction milestone.
Certificate of occupancy is issued and your ADU is ready to use.
What Made Building an ADU Easier, Faster, and More Valuable
Permit timeline
Effective January 2026, it puts your city on a clock: 15 business days to tell you whether your application is complete, then a 60-day window to approve or deny. If the city claims your submission is incomplete, you can now formally challenge that before a planning commission.
Junior ADUs
If a junior ADU has its own private bathroom, the requirement to live on site goes away. That matters if you are weighing an interior conversion instead of a detached backyard unit.
Coastal & rebuild
AB 462 sets a firm 60-day deadline on coastal permit decisions. AB 818 lets wildfire rebuilds move into a detached ADU before the main house is finished, with those permits fast-tracked to roughly 10 business days.
Transit corridors
Aimed at larger multifamily near transit rather than at detached ADUs. But if your home sits near a major transit stop, it can affect your land value and your long-term options.
California sets a baseline every city has to honor. Your city then layers its own process and review times on top.
Size
At least 800 sq ft
Regardless of lot-coverage limits. On request, at least 850 sq ft for a studio or one-bedroom, or 1,000 for two-plus bedrooms.
Setbacks
4 ft side & rear
From your side and rear property lines for a detached ADU.
Height
16-18 ft
Up to 16 ft for a detached ADU, or up to 18 ft near transit or on a multifamily lot.
City review
15 + 60 days
Under SB 543, 15 business days to confirm your application is complete, then 60 days to decide.
Not sure what your lot allows? A free estimate includes zoning, setbacks, and buildable size for your specific parcel.
Find your city for its local permit path, review times, and pricing.
Apex Homes floor plans are already approved with this city. Ask what that changes for your timeline.
FAQs
No. California requires a permit for every type of ADU, including detached units, attached units, garage conversions, and JADUs. Skipping it can lead to stop-work orders, fines, and problems when you refinance or sell, since lenders often will not count unpermitted square footage. The good news: Apex Homes handles the entire permitting process for you, from the application to plan check corrections and inspections.
Title 24 is California's collection of building standards. Part 6, the California Energy Code, sets energy-efficiency rules for insulation, windows, HVAC, water heating, lighting, ventilation, and solar. Yes, your ADU has to meet the requirements that apply to its project type and location. A new detached ADU is treated as new construction and commonly needs solar, while a garage conversion follows the rules for alterations. Every Apex Homes project includes the Title 24 energy report and solar design.
An ADU is a self-contained home on the same lot as your house: detached, attached, or a garage conversion, with its own kitchen, bathroom, and entrance, up to 1,200 sq ft for a detached unit. A JADU is capped at 500 sq ft and must be built inside your existing home. It needs its own entrance and at least an efficiency kitchen, but it can share a bathroom with the main house. Since January 2026, the owner only has to live on site if the JADU shares that bathroom.
Every ADU needs electricity, water, and sewer. Gas is optional, and most new ADUs go all-electric. In San Jose and most Bay Area cities, a detached ADU usually gets its own electrical panel and meter, while water and sewer typically extend from the main house, as long as the sewer lateral has the capacity and a dedicated cleanout. Combined hookups commonly run $8,000 to $23,000 or more depending on your site. Apex Homes starts the PG&E application before permits are final, so utility work runs alongside construction instead of after it.
No. Under AB 670 and Civil Code Section 4751, an HOA cannot ban or unreasonably restrict an ADU on a single-family lot. It can still apply published design standards, such as a matching architectural style, approved colors and materials, landscaping, and setbacks up to the state limit of 4 feet. It cannot require you to live on the property or ban long-term rentals. Condo associations can be treated differently, so get legal advice if that is your situation.
ADU permit costs in California typically range from about $1,000 to $30,000, depending on your city, the size of the ADU, and the scope of work. They usually cover plan check, the building permit and inspections, impact fees, and utility connection charges. ADUs under 750 sq ft are exempt from development impact fees, and pre-approved plans lower plan check costs. Our free estimate breaks down the fees for your specific city.
Zoning, buildable size, and permit path for your lot, in one call, at no cost.
