A detached ADU is a new, separate home built on the same lot as your house. It is the most private type of ADU and gives you the most freedom in layout, but it is also usually the most expensive, because everything from the foundation to the roof is new.
How big can a detached ADU be in Los Angeles?
As of October 2026, California law requires cities to allow a detached ADU of at least 850 sq ft, or 1,000 sq ft if it has more than one bedroom. Local lot coverage, floor area and open space rules cannot block an ADU of at least 800 sq ft with 4-foot side and rear setbacks. Size is measured as interior livable space.
Where a city has no compliant ADU ordinance, the state default maximum for a new detached ADU is 1,200 sq ft. In the City of Los Angeles, City Planning's ADU guidance caps detached ADUs at 1,200 sq ft, and hillside and baseline floor-area rules can limit size further on some lots.
How tall can a detached ADU be?
As of October 2026, state law sets a base height of 16 feet for a detached ADU. Cities must allow 18 feet if the lot is within half a mile of a major transit stop or high-quality transit corridor, with up to 2 more feet to match the roof pitch of the main house. Lots with an existing multistory multifamily building also get 18 feet. Cities may allow more.
How close to the property line can it go?
As of October 2026, cities cannot require more than 4-foot side and rear setbacks for an ADU under state law. Front setbacks can apply, but cannot block an 800 sq ft unit. Some cities add other spacing rules; Pasadena, for example, has its own standards for walls with windows and for equipment near the property line. See ADUs in Pasadena.
Do I need to add parking?
Often not. As of October 2026, state law bars cities from requiring parking for an ADU that is:
- within half a mile walking distance of public transit
- in an architecturally and historically significant historic district
- in an area where on-street parking permits are required but not offered to the ADU occupant
- within one block of a car share vehicle
Where parking can be required, it is capped at one space per unit or bedroom, whichever is less. We check your address against these exemptions during the lot check.
How much does a detached ADU cost in Los Angeles?
As of October 2026, published Los Angeles estimates commonly put new detached ADUs at about $300,000 to $450,000 or more. Design and engineering, permit fees, utility connections and trenching to the back of the lot all add to the total. Units of 750 sq ft or less are exempt from impact fees under state law. Read the full ADU cost guide.
Does a new detached ADU need solar panels?
In most cases, yes. As of October 2026, the HCD ADU Handbook notes that new detached ADUs generally must include solar under the California Energy Code, with some exceptions. ADUs built inside existing space or as additions are generally exempt. We size the system as part of the design.
Can I use a pre-approved plan?
Yes, in many cases. The Los Angeles Department of Building and Safety (LADBS) runs an ADU Standard Plan Program with designs already reviewed for building code compliance, including a city-owned plan that can be used free of charge. LADBS still reviews site-specific items such as zoning and the foundation, and a standard plan may not work for every lot. We can build from a standard plan or a custom design.
What does a detached ADU depend on?
- Yard size and shape. Setbacks, the main house and existing trees decide the footprint.
- Slope and soil. Hillside lots may need geotechnical work and more foundation.
- Utilities. The distance to sewer, water and electrical service, and whether your panel can handle the new load.
- Access. How materials and equipment reach the backyard.
- Local rules. Hillside, fire zone, historic or coastal rules where they apply.