ADU Size & Building Constraints – Los Angeles County
1. Size Limits
• Detached ADUs: Up to 1,200 sq. ft., regardless of lot size.
• Attached ADUs: Limited to 50% of the primary dwelling’s size, max 1,200 sq. ft.
• Junior ADUs (JADUs): Max 500 sq. ft., must be within the existing home.
2. Height Restrictions
• Single-story ADU: Max 16 feet tall.
• Two-story ADU: Allowed up to 18 feet if near transit or located in specific zones.
3. Setbacks
• Front yard: Must comply with zoning requirements.
• Side & rear yards: 4 feet minimum setback required.
• Garage conversions: No setback required if using the existing footprint.
4. Parking Requirements
• No additional parking is required if the property is within ½ mile of public transit.
• Otherwise, 1 parking space per ADU may be required.
5. Lot Coverage & Open Space
• Some cities may have maximum lot coverage limits, especially for small lots.
• Open space requirements apply in multifamily zones.

Height Limits for ADUs in Los Angeles County
The height limit for Accessory Dwelling Units (ADUs) in unincorporated Los Angeles County
depends on the type and location of the ADU:
1. Standard Height Limits
• Detached ADUs (Single-Story): 16 feet maximum.
• Detached ADUs (Two-Story or Above-Garage): Up to 25 feet, depending on zoning
and setbacks.
• Attached ADUs: Limited to the height of the primary residence, up to 25 feet in most
cases.
• Junior ADUs (JADUs): Must be within the existing structure, so height is not an issue.
2. Special Height Allowances
• Near Transit or in Higher-Density Areas:
o If within ½ mile of a major transit stop, detached ADUs can be up to 18 feet.
o Some multifamily properties may allow up to 25 feet based on local zoning.
• Over Garages/Existing Structures:
o Allowed up to two stories (up to 25 feet) in some cases.
o Must meet fire safety and setback requirements.

1. Detached ADUs
o Max Height: 16 feet (Standard)
o 18 feet if within ½ mile of a major transit stop (California Gov. Code §
65852.2(e)(1)(C)).
o Up to 25 feet may be allowed, depending on zoning and lot conditions (Los
Angeles County ADU Ordinance 22.140.640).
2. Attached ADUs
o Can match the height of the primary residence (up to two stories).
o Must comply with setbacks, fire safety, and local zoning limits.
3. ADU Above Garage or Existing Structure
o Allowed up to two stories, subject to zoning restrictions.
o Must meet a minimum 4-foot setback from side and rear property lines.
Additional Requirements:
• Subject to design and privacy regulations in some areas.
• HOAs and local zoning may impose additional height restrictions.

Yes, you can stack ADUs (build one on top of another) on multifamily properties, but not on
single-family lots.
Key Code References:
1. Multifamily Properties (Apartments, Duplexes, etc.)
o Up to 25% of existing units can be converted into ADUs (CA Gov. Code §
65852.2(e)(1)(B)).
o Two detached ADUs are allowed, and they can be stacked if zoning allows (LA
County ADU Ordinance 22.140.640).
o Max Height: Up to 25 feet, depending on zoning.
2. Single-Family Properties
o Stacking ADUs is NOT allowed; only one detached ADU + one JADU per lot

Yes, two ADUs can be attached, but only on multifamily properties—not single-family lots.
Key Rules & Codes:
1. Multifamily Properties (Apartments, Duplexes, etc.)
o Two detached ADUs are allowed and can be attached to each other, forming a
duplex-style ADU (LA County ADU Ordinance 22.140.640).
o Max Size: Each ADU can be up to 1,200 sq. ft.
o Height Limit: Typically 16-25 feet, depending on zoning.
2. Single-Family Properties
o Two detached ADUs are NOT allowed, so you cannot attach two ADUs.

Yes, roof decks on ADUs are allowed in Los Angeles County, but they must comply with
zoning, privacy, and height regulations.
Key Code References:
• Allowed if within the ADU’s height limit (typically 16-25 feet, depending on zoning).
• Must comply with privacy regulations (e.g., setbacks, screening) to avoid overlooking
neighboring properties (LA County ADU Ordinance 22.140.640).
• May require additional safety features, like guardrails, per California Building Code
(CBC) § 1015.

• Design & Materials
• Must be compatible with the primary dwelling in materials, colors, and style (LA
County ADU Ordinance 22.140.640.D.2).
• No specific architectural style is required, but it cannot contrast sharply with the main
home.
• Windows & Privacy
• Upper-floor ADUs must minimize direct views into neighboring yards (LA County
ADU Ordinance 22.140.640.D.4).
• Frosted glass or clerestory windows may be required for privacy.
• Roof Design
• Pitched or flat roofs allowed, but must match the primary structure if visually dominant
(LA County ADU Ordinance 22.140.640.D.3).
• Lighting & Entrances
• Exterior lighting must be shielded to prevent glare onto adjacent properties (LA County
ADU Ordinance 22.140.640.D.5).
• Separate entrance required, but it cannot face the street unless already existing (LA
County ADU Ordinance 22.140.640.D.6).

1. Standard Setbacks (LA Municipal Code § 12.22.A.33)
• Side & Rear Yards: 4 feet minimum
• Front Yard: Must comply with zoning setback requirements for the main dwelling.
2. Garage Conversions
• No additional setbacks required if using the existing footprint (CA Gov. Code §
65852.2(e)(1)(A)).
3. Multifamily Properties (LA Municipal Code § 12.22.A.33(c))
• Detached ADUs: 4-foot side and rear setbacks apply.
• Converted ADUs (inside existing structures): No setback required

Fire Separation (CRC § R302.1)
• Detached ADUs must be at least 10 feet from other structures unless fire-rated
construction is used.
Zoning Setbacks (LA County ADU Ordinance § 22.140.640)
• Side & Rear Setbacks: 4 feet minimum
• Attached ADUs: No separation required.
• Garage Conversions: No additional setback if within the existing footprint

General Rule:
• Not allowed unless it meets standard front yard setbacks for the zoning district. (LA
County ADU Ordinance § 22.140.640.B.2)
Exception:
• If adhering to front setbacks prevents an 800 sq. ft. ADU, the setback may be reduced to
allow construction. (CA Gov. Code § 65852.2(c))

No, LA County does not mandate a soils report, unless specific site conditions trigger it. This
could include hillside ADU’.
Yes, Los Angeles County requires a Coastal Development Permit (CDP) for developments
within the Coastal Zone, as mandated by the California Coastal Act. The specific requirements
and application process are detailed in Los Angeles County Code § 22.56.2550. Additionally,
the California Coastal Commission oversees these permits to ensure compliance with coastal
regulations.

If a parking space is required, it may be located within the setbacks and in an existing driveway as tandem parking. Parking spaces don’t need to be replaced when a garage,
carport, or covered parking structure is demolished in conjunction with the construction
of an ADU or converted to an ADU.

No, most of everything can be submitted electronically

1. General Requirement:
• One parking space per ADU is typically required.
2. Exemptions:
• No parking is required if the ADU:
o Is located within ½ mile of public transit.
o Is part of an existing primary residence or accessory structure.
o Is in a designated historic district.
o Is in an area where on-street parking permits are required but not offered to the
ADU occupant.
o Is within one block of a car share vehicle.
3. Replacement Parking:
• If a garage, carport, or covered parking is demolished or converted into an ADU,
replacement parking is not required.
These guidelines are outlined in the Los Angeles County Code § 22.140.640 and the California
Government Code § 65852.2.