Accessory Structures in Humboldt County, CA (2026)
3 rules for unincorporated Humboldt County, California.
Verified from official government sources
ADU Rules
Humboldt County permits accessory dwelling units (ADUs) and junior ADUs in any zone allowing single-family or multifamily residential use, with ministerial 60-day approval, 4-foot side/rear setbacks, detached size cap of 1,200 sq ft, attached cap of 50% of the primary residence, and a prohibition on short-term rentals of 30 days or less.
Humboldt County ADU rules (Section 314-69.05)
Significant RestrictionsHumboldt County Code section 314-69.05 (Inland), subsections 69.05.2, 69.05.3.4, 69.05.4.3, 69.05.4.5, 69.05.4.6
69.05.2 Accessory Dwelling Units Generally Permitted. Accessory dwelling units may be principally permitted in any zone that allows single family or multifamily dwelling residential use and includes a proposed or existing dwelling, if the General Provisions in 69.05.3 are met, and the ADU meets the Development Regulations and Standards of section 69.05.4. ... The county shall act on a complete ...
Shed & Carport Rules
One-story detached sheds 120 sq ft or smaller are exempt from a Humboldt County building permit under the adopted California Building Code, but they must still meet zoning setbacks and any utilities serving the shed require permits; defensible-space rules also apply on parcels of 1 acre or more.
Humboldt County shed permit and setback rules
Some RestrictionsCalifornia Building Code section 105.2, adopted by Humboldt County Code section 331-11; zoning under Humboldt County Code section 314-43; defensible space under section 3115-2
California Building Code section 105.2, as adopted by Humboldt County Code section 331-11, exempts the following from building permits: One-story detached accessory structures used as tool and storage sheds, playhouses and similar uses, provided the floor area does not exceed 120 square feet (11 m2). Exemption from the permit requirements of this code shall not be deemed to grant authorization ...
Garage Conversions
Humboldt County allows conversion of an existing garage or accessory structure into an ADU or JADU with zero required setback, ministerial approval, no separate utility connection fees, and no impact fees if under 750 sq ft; short-term rentals (30 days or less) remain prohibited.
Humboldt County garage-to-ADU conversion rules
Some RestrictionsHumboldt County Code section 314-69.05 (Inland), subsections 69.05.3.8.1, 69.05.4.1.3, and 69.05.4.5
69.05.3.8.1 ADU or JADU Within Existing Single Family Structure. One accessory dwelling unit per lot with a proposed or existing single-family dwelling if all of the following apply: (i) The accessory dwelling unit or junior accessory dwelling unit is within the proposed footprint of an existing or proposed single-family dwelling or accessory structure, and may include an expansion of not more ...
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