ADU Regulations in Mill Valley, California (2026)

Regulations at a glance

Local rules & notes

Mandatory Use of State Law: Because the City's local ordinance is non-compliant, they must process all applications using State ADU Law, which is generally more permissive than local codes. Ordinance Repeal Recommendation: HCD has formally recommended the City repeal Ordinance 1330 to prevent applicant confusion, as it contains non-compliant standards that are no longer enforceable.

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

Frequently asked questions about ADU regulations in Mill Valley

• What is the maximum ADU size in Mill Valley, California?

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

• What are the setback requirements for ADUs in Mill Valley?

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

• What is the maximum height for an ADU in Mill Valley?

  In Mill Valley, 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 Mill Valley or county planning for your zone.

• Is ADU approval ministerial in Mill Valley?

  In Mill Valley, 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; Mill Valley planning can confirm the exact process.

• Are there parking requirements for ADUs in Mill Valley?

  In Mill Valley, 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 Mill Valley planning for your address.