California ADU rules · Butte County
Can I Build an ADU in Chico?
Yes — you can build an ADU in Chico. California's statewide ADU law requires every city, including Chico, to approve a qualifying accessory dwelling unit by right, plus a junior ADU (JADU) on a single-family lot. What varies city to city are the local specifics below.
Can you build one?
ADUs allowed
CA state lawYes — by right
ADUs and JADUs are allowed by right in all residential and mixed-use zones; ministerial approval, no hearing.
Units on a single-family lot
Local rule1 attached OR 1 detached ADU AND/OR 1 JADU
Allows either 1 attached or 1 detached ADU, plus a JADU, on single-family lots.
Units on a multifamily lot
Local ruleup to 8 detached (not to exceed number of existing units); conversions: up to 25% of existing units (or at least 1)
Detached ADUs capped at 8 or number of existing units, whichever is less.
Junior ADU (JADU)
CA state lawAllowed
Up to 500 sq ft, within the walls of an existing single-family home (single-family lots only).
Size & height
Max detached ADU size
Local rule1,200 sq ft
Detached ADU max is 75% of main dwelling area, up to 1,200 sq ft if larger than 800 sq ft.
Max attached ADU size
Local rule50% of main residence, up to 1,200 sq ft if larger than 800 sq ft
Attached ADU max is 50% of main residence, up to 1,200 sq ft if larger than 800 sq ft.
Guaranteed minimum size
CA state law800 sq ft
An 800 sq ft ADU must be allowed regardless of FAR/lot-coverage caps; a city also cannot cap an attached ADU below 850 sq ft (1,000 for 2+ bedrooms).
Max JADU size
CA state law500 sq ft
Max height
CA state law16 ft
16 ft baseline; cities must allow 18 ft within ½ mi of a major transit stop or where the primary dwelling is two-story, and 20 ft on a lot with a multistory multifamily building.
Setbacks
Side setback
CA state law4 ft
A city cannot require more than 4 ft side or rear setback; conversions of existing structures are exempt.
Rear setback
CA state law4 ft
Front setback
CA state lawNo front setback may block the mandatory 800 sq ft / 16-ft / 4-ft-setback ADU; otherwise per base zone
Separation from main house
CA state lawNone required
No statewide separation requirement between the ADU and the primary dwelling.
Parking
Parking required
Local ruleUp to 1 space
1 space per ADU, in addition to main dwelling parking; exemptions apply.
Transit parking exemption
CA state lawYes — no parking required near transit & for conversions
No parking may be required within ½ mi walking distance of transit, in a historic district, for an ADU within an existing structure, within one block of car-share, or in certain permit-parking areas.
Garage-conversion replacement parking
Local ruleNot required
No replacement required when garage/carport/covered parking is converted or demolished for ADU.
Approval, timeline & cost
Approval path
CA state lawMinisterial (by right)
No public hearing or discretionary design review for a qualifying ADU.
Approval timeline
CA state law60 days
The agency must act within 60 days of a complete application — and the ADU is deemed approved if it does not.
Owner-occupancy
Local ruleOnly for a JADU
Owner-occupancy required only for JADUs; not for ADUs.
Impact-fee waiver
CA state lawWaived under 750 sq ft
An ADU of 750 sq ft or less pays no impact fees (the 750 sq ft threshold itself is exempt under § 66311.5); larger ADUs pay fees proportional to the primary dwelling. JADUs (≤ 500 sq ft) are exempt.
Permits required
CA state lawBuilding permit
Only a ministerial building permit — no conditional use permit or discretionary design review for a qualifying ADU.
Chico-specific factors that can change the answer
State law sets the floor, but these local conditions often decide whether a specific parcel works.
Fire access requirement
ADUs not adjacent to an alley must be within 150 ft of street access for fire protection; sprinklers not required unless main residence requires them.
Historic district parking exemption
ADUs in historic districts are exempt from parking requirements.
Chico allows either one attached or one detached ADU plus a JADU on single-family lots, with detached ADUs up to 1,200 sq ft (75% of main dwelling). Detached ADUs may be up to 25 ft tall on single-family lots, and parking is not required for ADUs in historic districts or near transit.
Frequently asked questions
Can I build an ADU in Chico?
Yes. California's statewide ADU law requires Chico to approve a qualifying accessory dwelling unit ministerial (by right), plus a junior ADU (JADU) on a single-family lot.
How big can an ADU be in Chico?
A detached ADU of at least 1,200 sq ft must be allowed, and an ADU of 800 sq ft can never be zoned out by floor-area or lot-coverage limits. A JADU can be up to 500 sq ft.
What are the setback requirements for an ADU in Chico?
Side and rear setbacks are limited to 4 ft. No front setback may block the mandatory 800 sq ft / 16-ft / 4-ft-setback ADU; otherwise per base zone.
Is parking required for an ADU in Chico?
Up to 1 space. No parking can be required within ½ mile of transit, for conversions, or for units inside the primary home. When a garage is converted, replacement parking is not required.
How long does ADU approval take in Chico?
A complete application must be acted on within 60 days, with ministerial (by right) — no public hearing or discretionary design review for a qualifying ADU.
Do I have to live on the property to build an ADU in Chico?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Chico Municipal Code §19.76.130 (Ord. 2610, latest cited)
- CMC §19.76.130(C)(2)
- CMC §19.76.130(C)(3)
- CMC §19.76.130(C)(4)(b)
- CMC §19.76.130(C)(4)(a)
- CMC §19.76.130(C)(16)
- CMC §19.76.130(C)(17)
- CMC §19.76.130(C)(13)
- CMC §19.76.130(C)(15)
- Cal. Gov. Code §§ 66310–66342 (ADU Law)
- HCD 2025 Accessory Dwelling Unit Handbook
- Cal. Gov. Code § 66317 (ministerial approval, 60-day deadline)
- Cal. Gov. Code § 66333 (junior ADUs)
- Cal. Gov. Code § 66321 (size minimums & height)
- Cal. Gov. Code § 66323 (by-right ADU/JADU, 800 sq ft, 4-ft setbacks)
- Cal. Gov. Code § 66322 (ADU parking; § 66334 covers JADU parking)
- Cal. Gov. Code § 66311.5 (impact fees: none for an ADU ≤ 750 sq ft or JADU ≤ 500 sq ft)
Last updated Ord. 2610 (latest cited). This is an AI-assisted summary of Chico's ADU rules, drawn from its published ordinance and California ADU law — general information, not legal advice, and it may be incomplete or out of date. Verify the controlling rule for your specific parcel with Chico Planning before relying on it.
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