ADU Regulations in Los Angeles County, California (2026)

Regulations at a glance

Local rules & notes

Methane Zone Mitigation: Special slab-on-grade requirements apply if the site is within a designated Methane Zone. Fire Rating Proximity Rule: Units located less than 3 feet from an adjacent structure require a 1-hour fire rating for exterior walls. School Fee Threshold Optimization: The standard plan is designed at 499 SF for school district calculations, likely to stay under the 500 SF threshold for school impact fees.

For the official ordinance and latest updates, check your city or county planning department.

Frequently asked questions about ADU regulations in Los Angeles County

• What is the maximum ADU size in Los Angeles County, California?

  In Los Angeles County, the maximum ADU size is typically 1200 square feet, depending on whether the unit is attached or detached. California state law allows up to 1,200 sq ft for detached ADUs and 800 sq ft for attached in many jurisdictions; Los Angeles County may follow state defaults or have local limits. Verify with Los Angeles County planning for your specific lot.

• What are the setback requirements for ADUs in Los Angeles County?

  In Los Angeles County, typical setback requirements are 4 feet from the side property line and 4 feet from the rear. These may be reduced to 4 feet under California Government Code § 65852.2 where applicable. Check with Los Angeles County planning for overlay zones or design standards that could affect your site.

• What is the maximum height for an ADU in Los Angeles County?

  In Los Angeles County, the maximum height for an ADU is generally 20 feet. State law often allows up to 16 feet for detached ADUs and up to 25 feet when within 4 feet of the property line in some cases. Confirm with Los Angeles County or county planning for your zone.

• Is ADU approval ministerial in Los Angeles County?

  In Los Angeles County, ADU approval is typically Ministerial (by-right) per Gov Code §65852.2. Ministerial (by-right) review means the city must approve qualifying applications without discretionary review, per California Gov Code § 65852.2. Your project must still meet objective standards; Los Angeles County planning can confirm the exact process.

• Are there parking requirements for ADUs in Los Angeles County?

  In Los Angeles County, parking for ADUs is generally true. California law often waives parking for ADUs within a half-mile of transit or in certain historic districts. Check with Los Angeles County planning for your address.