ADU Regulations in Napa County, California (2026)

Regulations at a glance

Local rules & notes

Illegal Deed Restriction Requirement: The County attempted to require owners to record a covenant/deed restriction to prohibit short-term rentals, which HCD identified as an unauthorized 'additional standard'. Multifamily ADU Expansion: Under SB 1211, the county must allow up to 8 detached ADUs on lots with existing multifamily dwellings, provided the number does not exceed the existing unit count. Unpermitted ADU Amnesty: The ordinance must be updated to include AB 2533 protections which facilitate the permitting of previously unpermitted ADUs and JADUs.

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

Frequently asked questions about ADU regulations in Napa County

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

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

• What are the setback requirements for ADUs in Napa County?

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

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

  In Napa County, 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 County or county planning for your zone.

• Is ADU approval ministerial in Napa County?

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

• Are there parking requirements for ADUs in Napa County?

  In Napa County, 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 County planning for your address.