ADU Regulations in Antioch, California (2026)

Regulations at a glance

Local rules & notes

Confusing Impact Fee Formula: The ordinance text provides an example for calculating proportional impact fees that appears mathematically inverted, suggesting the primary floor area be divided by the ADU floor area (resulting in a multiplier > 1), rather than the standard ADU/Primary ratio. Future Owner Occupancy Reinstatement: Unlike many cities that simply reference state law, Antioch's ordinance explicitly codes a 'sunset' on the owner-occupancy exemption, requiring deed restrictions to state that units created after Jan 1, 2025, will require owner occupancy. Front Setback Requirement: The city imposes a large 30-foot front setback, which is stricter than standard side/rear setbacks, though it yields to the state mandate allowing at least an 800 sqft unit.

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

Frequently asked questions about ADU regulations in Antioch

• What is the maximum ADU size in Antioch, California?

  In Antioch, the maximum ADU size is typically 1000 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; Antioch may follow state defaults or have local limits. Verify with Antioch planning for your specific lot.

• What are the setback requirements for ADUs in Antioch?

  In Antioch, 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 Antioch planning for overlay zones or design standards that could affect your site.

• What is the maximum height for an ADU in Antioch?

  In Antioch, the maximum height for an ADU is generally 16 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 Antioch or county planning for your zone.

• Is ADU approval ministerial in Antioch?

  In Antioch, 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; Antioch planning can confirm the exact process.

• Are there parking requirements for ADUs in Antioch?

  In Antioch, 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 Antioch planning for your address.