ADU Regulations in Trinity County, California (2026)

Regulations at a glance

Local rules & notes

Unpermitted ADU Amnesty: Local agencies are prohibited from denying permits for unpermitted ADUs built before 2020 unless they are a health and safety risk. HOA Review Prohibition: Homeowners' associations and third parties are legally barred from influencing or reviewing ADU permit applications. 60-Day Deemed Approved Rule: If the local agency does not approve or deny a completed application within 60 days, it is automatically deemed approved.

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

Frequently asked questions about ADU regulations in Trinity County

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

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

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

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

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

  In Trinity 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 Trinity County or county planning for your zone.

• Is ADU approval ministerial in Trinity County?

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

• Are there parking requirements for ADUs in Trinity County?

  In Trinity 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 Trinity County planning for your address.