ADU Regulations in San Dimas, California (2026)

Regulations at a glance

Local rules & notes

Clerestory Window Requirement: ADUs with side or rear setbacks less than 5 feet are restricted to clerestory windows at least 6 feet above the floor. Usable Open Space Requirement: ADUs must provide 100 square feet of usable open space, though this cannot preclude an 800 sq ft unit. Entrance Orientation Restrictions: ADU entrances cannot face the street and detached units cannot have entrances on elevations within 15 feet of a side property line. Equestrian Property Setback Flexibility: Special provisions allow for setback adjustments on equestrian properties if standard ADU setbacks are not physically feasible.

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

Frequently asked questions about ADU regulations in San Dimas

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

  In San Dimas, 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; San Dimas may follow state defaults or have local limits. Verify with San Dimas planning for your specific lot.

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

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

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

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

• Is ADU approval ministerial in San Dimas?

  In San Dimas, 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 Dimas planning can confirm the exact process.

• Are there parking requirements for ADUs in San Dimas?

  In San Dimas, 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 Dimas planning for your address.