ADU Regulations in Diamond Bar, California (2026)

Regulations at a glance

Local rules & notes

Home Improvement Program (HIP): Qualified low- and moderate-income households are eligible to receive up to $20,000 as a no-interest, deferred loan for housing rehabilitation, which can be a significant source of funding for ADU/JADU related improvements. 2021 Ordinance Update: The City amended its Development Code in 2021 to incorporate recent state ADU laws, ensuring compliance and removing outdated barriers.

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

Frequently asked questions about ADU regulations in Diamond Bar

• What is the maximum ADU size in Diamond Bar, California?

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

• What are the setback requirements for ADUs in Diamond Bar?

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

• What is the maximum height for an ADU in Diamond Bar?

  In Diamond Bar, 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 Diamond Bar or county planning for your zone.

• Is ADU approval ministerial in Diamond Bar?

  In Diamond Bar, 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; Diamond Bar planning can confirm the exact process.

• Are there parking requirements for ADUs in Diamond Bar?

  In Diamond Bar, 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 Diamond Bar planning for your address.