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What are the ADU setback rules in California, and how does Los Angeles apply them?

For a new ADU (accessory dwelling unit), California lets a city require a setback of no more than 4 feet from the side and rear lot lines, and no setback at all when you convert an existing structure such as a garage 1. Front setbacks can still apply, but a city cannot use them to block an ADU of at least 800 square feet with 4-foot side and rear setbacks 2. Los Angeles follows the same numbers, with a few rules of its own about where a detached unit can sit 811.

Edited by Ryan Rambo, construction managerFacts checked 2026-10-09

How close to the property line can I build a new ADU in California?

Four feet from the side and rear lot lines is the most a city can ask for. State law says a setback of no more than four feet from the side and rear lot lines shall be required for an ADU that is not converted from an existing structure 1. That applies to a new detached backyard house and to a new attached addition alike.

The state also guarantees one specific unit. On a lot with a single-family house, one detached, newly built ADU with 4-foot side and rear setbacks must be approved 3. A city cannot use lot coverage, floor area ratio, open space, front setbacks or minimum lot size to stop an ADU of at least 800 square feet with those 4-foot setbacks 2.

Los Angeles uses 4 feet for its own ADUs too. City Planning's ADU memo lists a 4-foot minimum side and rear yard for the new building or addition portion of an ADU 11. So on a typical San Fernando Valley lot, the line you design to is 4 feet in from the side and back fences, measured from the actual property line, not the fence.

Does a garage conversion have to meet setbacks?

No. State law says no setback shall be required for an existing living area or accessory structure that is converted to an ADU, or for a structure rebuilt in the same location and to the same dimensions 1. Los Angeles applies the same rule and says no additional setbacks are required in that case 11.

That is why an old garage sitting 2 feet off the back fence can become a backyard house where a new building could not go. The relief covers the existing footprint, though, not anything you add. City Planning gives the example of an ADU built above an existing garage on the property line: the garage portion does not have to meet the current setback, but the addition above it still has to maintain required setbacks 10.

A converted garage still has to meet the building code, and walls close to the line have fire-rating rules of their own. Our guide on checking whether your garage was permitted covers the records you need and the fire rules for conversions.

Can I put an ADU in my front yard?

Usually not in Los Angeles, unless the backyard cannot fit one. The City's ADU ordinance requires detached ADUs to be located behind the primary residence, with limited exceptions for through lots and for additions to an existing front-yard accessory structure 8.

The state puts a floor under that rule. A city may apply front yard setbacks to ADUs, but those setbacks cannot stop an ADU of at least 800 square feet from being built, even if it would sit partly or wholly in the front setback 4. The state handbook says that if an 800 square foot unit cannot be built in the backyard, the city must allow it in the front setback if that is necessary 5. Los Angeles says the same thing in its own memo: it may still apply front yard setbacks, but not to block an ADU of up to 800 square feet that cannot be built elsewhere on the lot 9.

There is one more case. For the ADUs that state law requires cities to approve under Government Code section 66323, the city cannot impose local standards, including front setbacks, and cannot require the unit to be built somewhere else on the lot 6.

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If I build 4 feet from the line, what does the building code add?

It adds fire rules for the wall facing the neighbor. Setbacks come from zoning; the building code separately decides how a wall near a property line must be built. Under the California Residential Code table for buildings without fire sprinklers, an exterior wall less than 5 feet from the line must be 1-hour fire-resistance rated, and a wall 5 feet or more away does not need a rating 14.

Windows and doors are limited too. In the same table, openings are not allowed less than 3 feet from the line, are capped at 25% of the wall area between 3 and 5 feet, and are unlimited at 5 feet or more 14. Buildings with fire sprinklers throughout follow a second table with different distances 14.

In practice that means a wall at exactly 4 feet is a rated wall with limited windows. Moving it to 5 feet gives up a foot of floor plan but frees the wall. That trade-off is worth deciding before plans are drawn, not after.

How far does the ADU have to be from my house?

State ADU law does not set a distance between an ADU and other structures on the lot, though a city may impose objective standards and every ADU must meet the building code 7. Los Angeles has a local item on this. The LADBS ADU plan check correction sheet, revised in 2021, includes an item to maintain a minimum 10-foot horizontal separation between an ADU or accessory building and the main building 15.

That correction sheet predates several rounds of state ADU changes, so treat the 10-foot item as something to confirm with plan check for your design, not as a settled rule. If your yard is tight, this is the number most likely to decide whether the backyard house fits, so ask early.

What if my lot has a narrow side yard or a building line?

A narrower side yard can work in your favor. City Planning says that when the required side yard for a lot under the zoning code is less than 4 feet, the lesser setback may be used 11.

A building line can work against you. City Planning treats building lines as functionally equivalent to setbacks in deciding where an ADU can go 12. If your street has one, it acts like a deeper front yard, and the front-setback protections above are what keep an 800 square foot unit possible.

How do I find my own setbacks before I pay for plans?

Start with ZIMAS, City Planning's online map, which looks up a parcel's zoning designation and its planning and building permit history 16. Then work through it in this order:

  1. Look up your address in ZIMAS and note the zone and any building line or special overlay.
  2. Pull the plot plan from your old building permits, which shows where the house and garage sit relative to the property lines. The garage permit guide explains how.
  3. Measure the backyard from an aerial image or by tape, and subtract 4 feet from the side and rear lines.
  4. Mark any existing garage or shed you might convert, since its footprint carries no setback 1.
  5. Check the distance to the house against the 10-foot item on the correction sheet 15.

Fences are often not on the property line, so a survey settles the exact line when the numbers are close. Putting these pieces together for one address is the kind of thing a lot check settles. For how tall the unit can be once it fits, see ADU height limits in LA, and for what fits on a typical lot, see ADU types on a 6,600 sq ft lot.

Quick answers

Can a California city require more than 4 feet of side or rear setback for an ADU?

No. For an ADU that is not a conversion, state law caps the side and rear setback at 4 feet 1.

Does a converted garage need any setback?

No setback is required for an existing structure converted to an ADU, or one rebuilt in the same place to the same size 111. Anything you add beyond that footprint must meet setbacks 10.

Do JADUs have setback rules?

A JADU sits inside the house, and Los Angeles requires side and rear setbacks sufficient for fire and safety, as determined by LADBS 13. See JADU vs ADU for the differences.

Can I put windows on a wall 4 feet from the property line?

Yes, but in a building without sprinklers, openings between 3 and 5 feet from the line are limited to 25% of the wall area, and the wall must be 1-hour rated 14.

Can Los Angeles make me build the ADU in the backyard?

Yes, the City requires detached ADUs behind the house 8, unless an 800 square foot unit cannot fit there, in which case the front setback must give way 59.

Sources

  1. Government Code section 66314, State of California (text via California.Public.Law). Facts checked 2026-10-09
  2. Government Code section 66321, State of California (text via California.Public.Law). Facts checked 2026-10-09
  3. Government Code section 66323, State of California (text via California.Public.Law). Facts checked 2026-10-09
  4. Accessory Dwelling Unit Handbook (March 2026): front setbacks, California Department of Housing and Community Development. Facts checked 2026-10-09
  5. Accessory Dwelling Unit Handbook (March 2026): alternate location, California Department of Housing and Community Development. Facts checked 2026-10-09
  6. Accessory Dwelling Unit Handbook (March 2026): state-law units, California Department of Housing and Community Development. Facts checked 2026-10-09
  7. Accessory Dwelling Unit Handbook (March 2026): distance between structures, California Department of Housing and Community Development. Facts checked 2026-10-09
  8. ZA Memo 143, Revision 1 (updated 8.1.25), Q.37, Los Angeles City Planning. Facts checked 2026-10-09
  9. ZA Memo 143, Revision 1 (updated 8.1.25), Q.37, Los Angeles City Planning. Facts checked 2026-10-09
  10. ZA Memo 143, Revision 1 (updated 8.1.25), Q.26, Los Angeles City Planning. Facts checked 2026-10-09
  11. ZA Memo 143, Revision 1 (updated 8.1.25), ADU summary table notes, Los Angeles City Planning. Facts checked 2026-10-09
  12. ZA Memo 143, Revision 1 (updated 8.1.25), Q.40, Los Angeles City Planning. Facts checked 2026-10-09
  13. ZA Memo 143, Revision 1 (updated 8.1.25), JADUs, Los Angeles City Planning. Facts checked 2026-10-09
  14. California Residential Code 2022, Section R302.1 and Table R302.1(1), UpCodes (code text). Facts checked 2026-10-09
  15. ADU Plan Check Correction Sheet (rev. 8/03/2021), LADBS. Facts checked 2026-10-09
  16. ZIMAS: Zoning Information and Map Access System, Los Angeles City Planning. Facts checked 2026-10-09

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Greenlight is not a contractor, architect or engineer, and this is not legal advice. Rules change; every fact here shows the date we last checked it.