ADU Regulations in Walnut, California (2026)

Regulations at a glance

Local rules & notes

Large ADU Sequencing Requirement: The city permits detached ADUs larger than 800 square feet (outside the state-exempt category) but mandates that they must be constructed before any other ADUs on the property. Pre-Reviewed ADU Plans (PRADU) Program: The city provides a specific program for pre-reviewed plans for detached new construction ADUs to streamline the ministerial review process. Faith-Based ADU Support: The city is recognized for a proactive approach toward facilitating ADUs on faith-based organization properties.

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

Frequently asked questions about ADU regulations in Walnut

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

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

• What are the setback requirements for ADUs in Walnut?

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

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

  In Walnut, 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 Walnut or county planning for your zone.

• Is ADU approval ministerial in Walnut?

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

• Are there parking requirements for ADUs in Walnut?

  In Walnut, parking for ADUs is generally Often waived per state law; check local ordinance. California law often waives parking for ADUs within a half-mile of transit or in certain historic districts. Check with Walnut planning for your address.