ADU Regulations in Fairfax, California (2026)

Regulations at a glance

Local rules & notes

Definition of ADU (Inclusionary Zoning): In Fairfax County, 'ADU' stands for Affordable Dwelling Unit, referring to below-market units within larger developments, not Accessory Dwelling Units (granny flats). Housing Trust Fund Equity Share: Upon the first sale after the 30-year control period expires, the seller must pay 50% of the net equity gain (difference between net sales price and adjusted original price) to the Housing Trust Fund. Priority Point System: A complex point system determines buyer eligibility, awarding points for living/working in the county, having dependents, and time in the program.

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

Frequently asked questions about ADU regulations in Fairfax

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

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

• What are the setback requirements for ADUs in Fairfax?

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

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

  In Fairfax, 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 Fairfax or county planning for your zone.

• Is ADU approval ministerial in Fairfax?

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

• Are there parking requirements for ADUs in Fairfax?

  In Fairfax, parking for ADUs is generally Often waived per state law; check local ordinance. California law often waives parking for ADUs within a half-mile of transit or in certain historic districts. Check with Fairfax planning for your address.