Butte County, CA Accessory Structures: ADU Rules (2026)
ADU rules in Butte County, CA, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- Code Section
- Butte County Code section 24-172
- Maximum detached ADU size
- 1,200 sq ft (minimum 150 sq ft)
- Maximum JADU size
- 500 sq ft (minimum 150 sq ft)
- Minimum side/rear setback
- 4 feet (or zero for conversions of existing structures)
- Maximum units per parcel
- 3 (primary + detached ADU + JADU)
- Short-term rental rule
- ADUs and JADUs cannot be rented for 30 days or less
- Geographic limit
- Only allowed where municipal water and sewer service is available
Summary
Butte County permits accessory dwelling units (ADUs) and junior ADUs in unincorporated areas served by municipal water and sewer, with ministerial approval, 4-foot side/rear setbacks, and size caps of 500 sq ft (JADU) or 1,200 sq ft (detached ADU); short-term rentals under 30 days are prohibited.
A. Purpose. The unincorporated area of Butte County is predominantly rural and includes large areas of actively farmed agricultural land, as well as timber producing land. Only very limited areas adjacent to the City of Oroville are served by water and sewer service providers. Butte County allows second units in most zones that allow residences (see Section 24-172.2). This section establishes standards for the location and construction of accessory dwelling units and junior accessory dwelling units in conformance with Section 65852.2 and Section 65852.22 of the California Government Code, in areas provided with municipal water and sewer service. B. Permit Process: 1. A permit application for an accessory dwelling unit or a junior accessory dwelling unit shall be considered and approved ministerially in the same manner as a building permit for a residence without discretionary review or a hearing, notwithstanding California Government Code Section 65901 or 65906 or any local ordinance regulating the issuance of variances or special use permits. C. Location. 1. Water and Sewer Service. Accessory dwelling units and junior accessory dwelling units may only be permitted in areas within the boundaries of water and sewer service providers and when water and sewer service connections are available. Accessory dwelling units and junior accessory dwelling units are not allowed in areas of the county that are not served by water and sewer service providers. E. Accessory Dwelling Unit Types and Sizes 1. Junior Accessory Dwelling Unit: ... a. Size: Shall be a minimum of 150 square feet and not exceed 500 square feet. 2. Accessory Dwelling Unit, Detached: ... a. Size: Shall be a minimum of 150 square feet and not exceed 1,200 square feet. H. Development Standards. 1. Setbacks. ... b. If the parcel cannot accommodate the setback imposed by the applicable zone, the setback maybe no less than 4 feet from side and rear property lines for new accessory dwelling units not developed within or converted from an existing structure. 5. Rental Term: Accessory dwelling units and junior accessory dwelling units shall be not be rented or offered for rent for a term of 30 days or less.
Full Breakdown
22. 2 remain available on parcels with approved septic and wells. Permit applications are processed ministerially without discretionary review or a hearing. Junior ADUs must be a minimum of 150 sq ft and not exceed 500 sq ft; detached ADUs must be a minimum of 150 sq ft and not exceed 1,200 sq ft; attached ADUs are limited to 50 percent of the floor area of the primary dwelling. Setbacks for new ADUs are no less than 4 feet from side and rear property lines, and conversions of existing structures into ADUs require no additional setback.
Up to three units per parcel are allowed (one primary dwelling, one detached ADU, and one JADU). Impact fees are prohibited on ADUs under 750 sq ft, and ADUs are not allowed on parcels subject to Williamson Act contracts. ADUs and JADUs cannot be rented for terms of 30 days or less, and the owner must record a deed restriction containing this prohibition before the permit issues.
Violations & Fines
Building or renting an ADU without recording the required deed restriction, exceeding size caps, or renting an ADU for terms of 30 days or less can trigger code enforcement action by the county, withholding of certificate of occupancy, and legal action against the property owner. Williamson Act parcels that build an ADU may face contract cancellation.
Frequently Asked Questions
Can I build an ADU on my unincorporated Butte County property?
Do I need a public hearing to get an ADU approved?
Can I Airbnb my ADU?
Sources & Official References
Other rules in Butte County
How Butte County compares: Easiest Cities to Build an ADU·California rules heatmap·Compare Butte County to another location·View the California accessory structures overview
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