ADU Permit Guide for Los Angeles, Orange County & San Bernardino

An ADU permit is the official building permit and related approvals that authorize construction or conversion of an accessory dwelling unit on a residential property in California. Accessory dwelling units, also called in-law units, granny flats, casitas, or cottages, are secondary housing units that function as independent living space with their own kitchen, bathroom, and exterior access. Almost every ADU, whether it is a detached ADU, attached ADU, garage conversion, or junior ADU, requires a building permit before any construction begins, and building an ADU often takes a combination of different permit approvals, including specific permits for utility connections and sanitation. Your ADU permit verifies compliance with the California Building Code, the Residential Code, the energy code (Title 24), the fire code, and local development standards. Skipping it carries real risk. Building without a permit can lead to stop-work orders and municipal fines, denial of homeowner insurance claims, an inability to sell or refinance the property, and even orders to demolish unpermitted ADUs. Even a simple garage conversion almost always requires a full building permit plus electrical, plumbing, and mechanical permits, so the permit process is the foundation every legal, rentable unit is built on.

California has passed a series of ADU laws over the past several years to speed up approvals, limit what local governments can restrict, and add more housing units statewide. The important thing to understand is that local ADU ordinances must comply with these state minimum standards, even if a city’s older zoning code looks more restrictive. Under current California law, the framework that shapes almost every permit application looks like this:

• Ministerial, 60-day review: a complete ADU permit application must be approved or denied within 60 days, with no discretionary public hearing for a standard ADU
• One ADU plus one junior ADU is allowed on many single family home lots
• Impact fees are prohibited on ADUs under 750 square feet, which lowers the cost of smaller builds
• Owner-occupancy is not required for most newly permitted standard ADUs, so you can rent both the main home and the unit
• Homeowner associations cannot outright ban ADUs on single family homes, though they can apply reasonable design rules

Because ADU regulations still differ by city and county, the exact fees, forms, and design rules vary between Los Angeles, Long Beach, Anaheim, and other jurisdictions. What does not change is that cities across Los Angeles, Orange, and San Bernardino Counties must align their local ADU ordinances with these state minimums. Renova Built tracks the current rules in each city we serve, so your plans are built to comply from the first submittal.

Development standards are the rules about maximum size, height, setbacks, and lot coverage that a plan checker applies to your permit application. These physical dimensions decide what you can build and where. Under current California law, cities cannot restrict qualifying ADUs below a set of statewide minimums, which gives you a baseline you can count on no matter how strict a local code appears.

• At least 800 square feet is allowed for qualifying ADUs, even on tight lots
• A 16-foot height minimum applies in many zones, and cities can allow more
• 4-foot side and rear setbacks apply to qualifying detached and attached ADUs
• Detached ADUs are commonly capped around 1,000 to 1,200 square feet
• A junior ADU cannot exceed 500 square feet and must sit within your existing home

On a typical 6,000 square foot R1 lot in Los Angeles, a homeowner can generally place a detached ADU of up to 1,200 square feet in the rear yard with 4-foot setbacks, provided the unit meets height and code requirements. A state-exempt 800 square foot ADU usually cannot be denied solely because of lot coverage limits if it otherwise meets the minimum standards. This is why the exemption path matters so much, and why we weigh it against a larger local-ordinance unit for every homeowner.

California ADU laws greatly reduced parking requirements to make ADU development feasible on urban lots. As a rule, parking for an ADU generally cannot exceed one parking space per unit or per bedroom, whichever is less, and tandem or setback parking counts toward that requirement. In many cases, no new parking can be required at all under certain conditions.

• The ADU is within a half mile walking distance of public transit
• The ADU is located in a historic district
• The ADU is inside an existing primary dwelling or an existing accessory structure
• On-street parking permits are not offered in the area

Just as important, when an existing garage, carport, or covered parking is converted into an ADU, the city cannot require you to replace that parking on-site under current state law. For example, a garage conversion a third of a mile from a Metro bus stop in Los Angeles ends up with zero added parking requirements. That single rule is a big reason garage conversions are one of the most permit-friendly ways to add a unit.