California ADU rules · Sonoma County
Can I Build an ADU in Cotati?
Yes — you can build an ADU in Cotati. California's statewide ADU law requires every city, including Cotati, 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
Local ruleConditional
Ministerial if within local and state standards; discretionary review required if exceeding local standards.
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
Local ruleconversions (>=1 or 25% of units) + up to 2 detached (proposed multifamily) or up to 8 detached (existing multifamily), not to exceed number of existing units
Local code distinguishes between proposed and existing multifamily dwellings for detached ADUs.
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
Absolute local cap is 1,200 sq ft; lower caps (850/1,000) apply on lots <21,780 sq ft unless discretionary review.
Max attached ADU size
Local rule50% of primary, >=800
Attached ADU may be up to 50% of primary residence, but not less 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
Local rule18 ft
Detached ADU max height is 18 ft; attached ADU max height is 25 ft.
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
Local ruleNo ADU >800 sq ft may be located in the front or street side setback
Front setback restriction applies to ADUs over 800 sq ft.
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; no parking required for JADUs; state 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
CA state lawNot required
When a garage/carport is demolished or converted to build an ADU, replacement parking cannot be required.
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
No owner-occupancy for ADUs; JADU or primary must be owner-occupied unless exempted.
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.
Cotati-specific factors that can change the answer
State law sets the floor, but these local conditions often decide whether a specific parcel works.
Coastal Zone
ADUs must comply with Coastal Act resource protection policies in addition to state/local ADU law.
Cotati imposes a 1,200 sq ft absolute cap on detached ADUs, with lower caps for smaller lots unless discretionary review is obtained. ADUs over 800 sq ft are not allowed in the front or street side setback.
Frequently asked questions
Can I build an ADU in Cotati?
Yes. California's statewide ADU law requires Cotati 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 Cotati?
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 Cotati?
Side and rear setbacks are limited to 4 ft. No ADU >800 sq ft may be located in the front or street side setback.
Is parking required for an ADU in Cotati?
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 Cotati?
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 Cotati?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Cotati Municipal Code § 17.42.170
- Cotati Municipal Code § 17.42.170(A)
- Cotati Municipal Code § 17.42.170(B); Gov. Code § 66323
- Cotati Municipal Code § 17.42.170(B)(5)(a)-(c)
- Cotati Municipal Code § 17.42.170(B)(5)(d)
- Cotati Municipal Code § 17.42.170(B)(7)
- Cotati Municipal Code § 17.42.170(D)
- Cotati Municipal Code § 17.42.170(B)(6)
- Cotati Municipal Code § 17.42.170; Gov. Code § 66329
- Cal. Gov. Code §§ 66310–66342 (ADU Law)
- HCD 2025 Accessory Dwelling Unit Handbook
- 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 § 66314 (local ordinance standards)
- Cal. Gov. Code § 66317 (ministerial approval, 60-day deadline)
- Cal. Gov. Code § 66311.5 (impact fees: none for an ADU ≤ 750 sq ft or JADU ≤ 500 sq ft)
Last updated downloaded 2026-05-11. This is an AI-assisted summary of Cotati'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 Cotati Planning before relying on it.
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