ADU Regulations in Riverside, California (2026)

Regulations at a glance

Local rules & notes

Unpermitted Structure Protection: The County cannot deny an ADU permit due to unpermitted structures on the lot unless they are a health/safety threat or affected by the ADU construction. Fire Sprinkler Trigger Prohibition: The construction of an ADU cannot be used as a trigger to require the installation of fire sprinklers in the existing primary dwelling. Mobilehomes vs Manufactured Homes: The ordinance incorrectly allowed 'mobilehomes' (pre-1976); HCD clarifies only 'manufactured homes' (post-1976) are legally defined as ADUs.

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

Frequently asked questions about ADU regulations in Riverside

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

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

• What are the setback requirements for ADUs in Riverside?

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

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

  In Riverside, 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 Riverside or county planning for your zone.

• Is ADU approval ministerial in Riverside?

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

• Are there parking requirements for ADUs in Riverside?

  In Riverside, 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 Riverside planning for your address.