ADU Regulations in Colusa County, California (2026)

Regulations at a glance

Local rules & notes

Minimum Lot Size Restriction: The code imposes a minimum lot size of 9,600 sq ft for detached secondary units, which likely conflicts with California state law prohibiting minimum lot size requirements for ADUs. Restrictive Attached Size Limit: Attached units are limited to 30% of the existing living area, whereas state law typically allows up to 50%. Standard Setbacks Applied: The code requires ADUs to meet the setbacks of the underlying zone, rather than the state maximum of 4 feet for side and rear setbacks.

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

Frequently asked questions about ADU regulations in Colusa County

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

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

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

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

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

  In Colusa 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 Colusa County or county planning for your zone.

• Is ADU approval ministerial in Colusa County?

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

• Are there parking requirements for ADUs in Colusa County?

  In Colusa 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 Colusa County planning for your address.