ADU Regulations in Humboldt County, California (2026)

Regulations at a glance

Local rules & notes

Moveable Tiny Homes Permitted: Tiny Homes (as defined in County Code) may qualify as ADUs if they comply with detached ADU requirements and tiny home standards. Unlimited Size on Large Agricultural Lots: ADUs located on Agricultural Exclusive (AE) lots that are 40 acres or greater do not have a maximum square footage limit. Amnesty / Enforcement Delay: Owners of existing unpermitted ADUs built before the ordinance effective date may request a 5-year delay in enforcement upon receiving a violation notice. Special Permit Areas: ADUs in mapped hazard areas (fire, airport, landslide, flood, toxic sites) require a Special Permit and substantial evidence that safety conditions do not apply.

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

Frequently asked questions about ADU regulations in Humboldt County

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

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

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

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

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

  In Humboldt 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 Humboldt County or county planning for your zone.

• Is ADU approval ministerial in Humboldt County?

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

• Are there parking requirements for ADUs in Humboldt County?

  In Humboldt 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 Humboldt County planning for your address.