ADU Regulations in Napa, California (2026)

Regulations at a glance

Local rules & notes

SB 1211 Multifamily Allowance: Allows up to 8 detached ADUs on lots with existing multifamily dwellings, provided the number does not exceed the number of existing units. Front Setback Protection: Local agencies cannot impose front setbacks that would preclude an 800 square foot ADU with 4-foot side/rear setbacks. Unpermitted Structure Amnesty: The city cannot deny an ADU permit solely to require the correction of unpermitted structures that do not pose a health or safety threat.

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

Frequently asked questions about ADU regulations in Napa

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

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

• What are the setback requirements for ADUs in Napa?

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

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

  In Napa, 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 Napa or county planning for your zone.

• Is ADU approval ministerial in Napa?

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

• Are there parking requirements for ADUs in Napa?

  In Napa, 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 Napa planning for your address.