California ADU rules · Napa County
Can I Build an ADU in Calistoga?
Yes — you can build an ADU in Calistoga. California's statewide ADU law requires every city, including Calistoga, 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
Local ruleconversions (>=1 or 25% of units) + up to 2 detached
Local cap of 2 detached ADUs on multifamily lots, not 8 as in state baseline.
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 rule1,000 sq ft
Detached ADUs: 850 sq ft (studio/1-bed), 1,000 sq ft (2+ bed); 1,000 is the local maximum.
Max attached ADU size
Local rule50% of primary, >=850 (>=1,000 for 2+ bedrooms)
Explicitly matches state minimums but codified locally.
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 rule16 ft
Detached ADU: 16 ft standard; 18 ft near transit/multistory; attached: up to 25 ft or primary dwelling height, whichever is lower.
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 ruleNone
No parking required for ADU or JADU on single-family lots; 1 per detached ADU/JADU on multifamily unless exempt.
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 conversions.
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 ADUs.
Impact-fee waiver
Local ruleWaived under 750 sq ft
No impact fees for ADUs <750 sq ft or any JADU; proportional fees for ADUs ≥750 sq ft.
Permits required
Local ruleBuilding permit
Building permit required; utility/capacity fees may apply for new construction or >150 sq ft expansion.
Calistoga-specific factors that can change the answer
State law sets the floor, but these local conditions often decide whether a specific parcel works.
Fire sprinklers
Fire sprinklers required for ADUs only if required for the primary dwelling.
Historic district parking exemption
No parking required for ADUs in historic districts.
Hillside (RR-H) zones
ADUs allowed in hillside zones per Ch. 17.15, subject to Ch. 17.37.
Calistoga sets a local maximum detached ADU size of 1,000 sq ft (2+ bedrooms) and allows only 2 detached ADUs on multifamily lots. No parking is required for ADUs or JADUs on single-family lots, and fire sprinklers are required only if the main house needs them.
Frequently asked questions
Can I build an ADU in Calistoga?
Yes. California's statewide ADU law requires Calistoga 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 Calistoga?
A detached ADU of at least 1,000 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 Calistoga?
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 Calistoga?
None. 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 Calistoga?
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 Calistoga?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Calistoga Municipal Code (CMC) Chapter 17.37, last amended by Ord. 770, 2024
- CMC § 17.37.020
- CMC § 17.37.050(A)
- CMC § 17.37.050(A)(3)
- CMC § 17.37.050(C)
- CMC § 17.37.050(E)
- CMC § 17.37.050(E)(2)
- CMC § 17.37.030(A)
- CMC § 17.37.040(D)
- CMC § 17.37.050
- CMC § 17.37.050(F)
- CMC § 17.15.020
- 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)
Last updated 2026-06-25. This is an AI-assisted summary of Calistoga'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 Calistoga Planning before relying on it.
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