The rules that decide what you can build in your backyard: size, height, setbacks, parking, owner-occupancy and the pre-approved plan shortcut.
If you own a single-family lot in Los Angeles, you can almost certainly build an accessory dwelling unit. State law overrode most local restrictions, and the City of Los Angeles added a pre-approved standard plan program that cuts review time. Here are the rules that decide what fits on your lot, written for homeowners rather than planners.
Size and height
- Detached ADU: up to 1,200 square feet in most cases. Lots with a small main house may be limited to a percentage of the primary dwelling's floor area, with an 800 sq ft minimum always allowed.
- Attached ADU: up to 50 percent of the main house's floor area, or 800 sq ft if that is larger.
- Junior ADU: up to 500 sq ft carved out of the existing house, sharing a wall and sometimes a bathroom.
- Height: 16 feet for a detached unit by right, higher in some cases near transit or when matching a two-story main house.
Setbacks and placement
A detached ADU needs 4 feet from the rear and side property lines. Converting an existing garage or structure keeps its current setbacks even if they are less than 4 feet. Front-yard setbacks still apply, and hillside, historic and very-high fire-hazard overlays add review steps but rarely prohibit an ADU outright.
Parking
No replacement parking can be required for a garage converted to an ADU. New detached ADUs within half a mile of transit, or on lots where on-street permit parking is available, are also exempt. In practice most LA lots owe no ADU parking at all.
Owner-occupancy and rentals
Owner-occupancy requirements for ADUs are suspended statewide through at least 2025 and the City of LA does not enforce one. Long-term rental (30 days or more) is allowed. Short-term rental of an ADU is restricted under LA's home-sharing ordinance.
The pre-approved standard plan shortcut
LADBS maintains a list of pre-approved detached ADU plans from local designers. Using one means plan check focuses on site-specific items, which can cut weeks from review. We use standard plans when the lot allows and custom plans when it does not.
What still trips people up
- Sewer capacity and route. A long run or a grade problem can mean an ejector pump.
- Electrical service. Many 100-amp panels need an upgrade before an ADU is added.
- Fire sprinklers. Not required for an ADU unless the main house has them.
- Trees. Protected trees near the build area need a report.
- HOA rules. An HOA cannot prohibit an ADU but can enforce reasonable design rules.
Fix Brothers builds detached ADUs and garage conversion ADUs across the Valley, from Chatsworth and Granada Hills to Sherman Oaks and Burbank. If you are deciding between an ADU and adding to the main house, read room addition vs. moving.
Detached ADU, garage conversion or junior ADU: which fits
- Garage conversion: fastest and least expensive; keeps existing setbacks; no parking replacement.
- Detached new build: most flexible layout and highest rental value; needs 4-foot setbacks and a full foundation.
- Attached addition ADU: shares a wall with the house; good when the yard is small.
- Junior ADU: up to 500 sq ft inside the existing house; cheapest, but shares utilities and often a bathroom.
Frequently asked questions
How big can an ADU be in Los Angeles?
Detached units up to 1,200 sq ft in most cases; attached units up to 50 percent of the main house or 800 sq ft; junior ADUs up to 500 sq ft.
Do I need to live on the property to build an ADU?
Owner-occupancy requirements are suspended statewide and LA does not enforce one for ADUs.
Can my HOA stop me from building an ADU?
No. HOAs can enforce reasonable design standards but cannot prohibit an ADU.
Do I need parking for a new ADU?
Usually not. Garage conversions and most lots near transit or permit parking are exempt.
How long does ADU approval take in LA?
With a pre-approved standard plan, often 4-8 weeks. Custom plans typically 8-12 weeks including corrections.
Related services
Book a free on-site estimate: call (323) 593-3663 or request a quote online. Fix Brothers is a licensed and insured general contractor based in Chatsworth, serving Los Angeles since 2015.