ADU Regulations in San Marino, California (2026)

Regulations at a glance

Local rules & notes

Illegal Fire Safety Restrictions: The city attempted to restrict ADUs to lots with 10-foot wide fire lanes and specific water flow minimums without providing substantial evidence of health and safety risks. Subjective Design Standards: San Marino requires ADUs to 'exactly match' the primary residence and 'avoid direct line of sight' to neighbors, which are prohibited subjective standards. Prohibited Utility Requirements: The ordinance incorrectly stated that ADUs may not have separate utility services, which contradicts state protections for specific ADU types.

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

Frequently asked questions about ADU regulations in San Marino

• What is the maximum ADU size in San Marino, California?

  In San Marino, the maximum ADU size is typically 800 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; San Marino may follow state defaults or have local limits. Verify with San Marino planning for your specific lot.

• What are the setback requirements for ADUs in San Marino?

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

• What is the maximum height for an ADU in San Marino?

  In San Marino, 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 San Marino or county planning for your zone.

• Is ADU approval ministerial in San Marino?

  In San Marino, 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; San Marino planning can confirm the exact process.

• Are there parking requirements for ADUs in San Marino?

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