California ADU rules · Mendocino County
Can I Build an ADU in Willits?
Yes — you can build an ADU in Willits. California's statewide ADU law requires every city, including Willits, 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
CA state law1 ADU + 1 JADU
At least one ADU and one JADU per single-family lot (a conversion ADU may also be possible).
Units on a multifamily lot
CA state lawConversion ADUs (≥1, up to 25% of units) + up to 8 detached
Conversions of non-livable space (at least 1, or up to 25% of existing units) plus up to 8 detached ADUs on a lot with existing multifamily — never exceeding the number of existing units. JADUs are single-family only.
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
Local maximum for detached ADUs is 1,200 sq ft.
Max attached ADU size
Local rule50% of primary dwelling or 1,200 sq ft, whichever is less
Attached ADUs capped at 50% of primary or 1,200 sq ft, whichever is less.
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
Local rule25 ft
ADUs may be up to two stories or 25 feet in height.
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
Local rule10 ft
Detached ADUs must be at least 10 feet from the primary dwelling.
Parking
Parking required
Local ruleUp to 1 space
No more than one off-street parking space per ADU; exemptions per state law.
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 parking required for garage/carport conversion to 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
CA state lawOnly for a JADU
No owner-occupancy requirement for ADUs (the prior sunset was removed). A JADU may require owner-occupancy, principally where it shares sanitation with the main house.
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
Local ruleBuilding permit
Building permit required; utility connection rules depend on ADU type.
Willits sets a 1,200 sq ft maximum for both detached and attached ADUs and allows up to 25 ft height. Detached ADUs must be at least 10 feet from the primary dwelling, and ADUs above garages require 5 ft side/rear setbacks.
Frequently asked questions
Can I build an ADU in Willits?
Yes. California's statewide ADU law requires Willits 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 Willits?
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 Willits?
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 Willits?
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 Willits?
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 Willits?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Willits Municipal Code Chapter 17.61 (Ord. No. 18-03, 9-26-18)
- Willits Municipal Code § 17.61.030(B)(5)
- Willits Municipal Code § 17.61.030(B)(4)
- Willits Municipal Code § 17.61.030(B)(17)
- Willits Municipal Code § 17.61.030(B)(10)
- Willits Municipal Code § 17.61.030(B)(11)-(12)
- Willits Municipal Code § 17.61.030(B)(13)
- Willits Municipal Code § 17.61.030(B)(15)-(16)
- 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 § 66323 (by-right ADU/JADU, 800 sq ft, 4-ft setbacks)
- Cal. Gov. Code § 66333 (junior ADUs)
- Cal. Gov. Code § 66321 (size minimums & height)
- Cal. Gov. Code § 66322 (ADU parking; § 66334 covers JADU parking)
- Cal. Gov. Code § 66315 (owner-occupancy)
- Cal. Gov. Code § 66311.5 (impact fees: none for an ADU ≤ 750 sq ft or JADU ≤ 500 sq ft)
Last updated 2026-06-25. This is an AI-assisted summary of Willits'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 Willits Planning before relying on it.
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