ADU Regulations in Solano County, California (2026)

Regulations at a glance

Local rules & notes

Rural Residential Size Bonus: In R-R zoning districts, detached ADUs are permitted to reach a gross floor area of 1,500 square feet, exceeding the standard 1,200 square foot limit found in most California jurisdictions. Neighborhood Compatibility Waiver: The Zoning Administrator has the authority to grant waivers for minimum development and architectural standards if the unit is compatible with the surrounding neighborhood. Fire Sprinkler Waiver: ADUs and JADUs are exempt from fire sprinkler requirements if the primary residence does not have them, providing a significant cost saving for older homes.

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

Frequently asked questions about ADU regulations in Solano County

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

  In Solano County, the maximum ADU size is typically 1500 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; Solano County may follow state defaults or have local limits. Verify with Solano County planning for your specific lot.

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

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

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

  In Solano 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 Solano County or county planning for your zone.

• Is ADU approval ministerial in Solano County?

  In Solano 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; Solano County planning can confirm the exact process.

• Are there parking requirements for ADUs in Solano County?

  In Solano County, 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 Solano County planning for your address.