Glenn County, CA Accessory Structures: ADU Rules (2026)
ADU rules in Glenn County, CA, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- County code chapter
- Glenn County Code Ch. 15.175 (procedure) & Ch. 15.590 (standards)
- County ADU term
- 'Second dwelling' / second dwelling unit
- Foundation & entrance
- Permanent foundation; separate entrance (Sec. 15.590.020(B))
- County size limit
- No maximum size if within lot coverage (cites Gov. Code 65852.2)
- Controlling state law
- Cal. Gov. Code 66310-66342 (ministerial; preempts local rules)
- State-exempt ADU minimum
- 800 sq ft, 16 ft, 4 ft setbacks (Gov. Code 66323)
Summary
In unincorporated Glenn County, ADUs are permitted as 'second dwellings' under Chapter 15.175 and built to the standards of Chapter 15.590 of the Unified Development Code. The county code references older state law, but current California Government Code Sections 66310-66342 control and require ministerial approval.
In accordance with California Government Code Sections 65852.2 (a)(1)(B)(i) and 68582.2(c), no maximum size is imposed on second dwellings provided that it does not exceed lot coverage requirements.
Full Breakdown
590 (Minimum Residential Construction Standards), and is approved once the Planning Director determines it complies. 610 is waived where there is insufficient space for an additional vehicle. 2(a)(1)(B)(i), no maximum size is imposed on a second dwelling so long as it does not exceed lot coverage requirements. 2. State ADU law has since been recodified into Government Code Sections 66310-66342 (effective January 1, 2025). Under that controlling state law, an ADU and a junior ADU (JADU) must be approved ministerially; a 'state-exempt' ADU under Section 66323 must be allowed at up to 800 square feet and 16 feet in height with 4-foot side and rear setbacks regardless of local lot-coverage or design standards, and a JADU is limited to 500 square feet within an existing single-family residence.
Where the county's older ordinance conflicts with current state law, state law preempts. Owners should confirm requirements with Glenn County Planning & Community Development Services.
Violations & Fines
Building or occupying a second dwelling/ADU without a building permit and second-dwelling approval, or in violation of the Chapter 15.590 construction standards, is a violation of the Glenn County Unified Development Code subject to code enforcement. Where county standards are more restrictive than California Government Code Sections 66310-66342, the qualifying ADU must still be approved ministerially under state law; unpermitted units are ineligible for that streamlined approval and may be abated as zoning and building-code violations.
Frequently Asked Questions
Can I build an ADU on my property in unincorporated Glenn County?
How large can my ADU be in Glenn County?
Does Glenn County's ADU code match current California law?
Sources & Official References
Other rules in Glenn County
How Glenn County compares: Easiest Cities to Build an ADU·California rules heatmap·Compare Glenn County to another location·View the California accessory structures overview
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