California ADU rules · Siskiyou County
Can I Build an ADU in Dunsmuir?
Yes — you can build an ADU in Dunsmuir. California's statewide ADU law requires every city, including Dunsmuir, 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 per multifamily lot; state allows up to 8.
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
1,200 sq ft max only on parcels ≥10,000 sq ft; smaller parcels have lower caps.
Max attached ADU size
Local rule800 sq ft or 50% of existing living area, whichever is greater
Local rule allows attached ADUs to exceed 800 sq ft if 50% of primary is greater.
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
18 ft for 1-story detached; up to 25 ft for 2-story or attached ADUs.
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
Max 1 space per unit or per bedroom, whichever is less; tandem allowed.
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.
Approval, timeline & cost
Approval path
CA state lawMinisterial (by right)
No public hearing or discretionary design review for a qualifying ADU.
Approval timeline
Local rule60 days
60-day ministerial approval timeline for ADUs and JADUs.
Owner-occupancy
Local ruleOnly for a JADU
Owner-occupancy required for JADUs; not required for ADUs until Jan 1, 2025.
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; application to city clerk or designee.
Dunsmuir-specific factors that can change the answer
State law sets the floor, but these local conditions often decide whether a specific parcel works.
Fire protection requirements
Sprinklers not required unless for primary; fire chief may require extra protection if setbacks not met.
Historic district rental restriction
ADUs cannot be used as short-term rentals; minimum rental period 30 days.
Dunsmuir limits detached ADUs on multifamily lots to 2 per parcel and sets a 1,200 sq ft max for detached ADUs only on parcels 10,000 sq ft or larger. Owner-occupancy is required for JADUs, and ADUs cannot be used as short-term rentals.
Frequently asked questions
Can I build an ADU in Dunsmuir?
Yes. California's statewide ADU law requires Dunsmuir 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 Dunsmuir?
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 Dunsmuir?
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 Dunsmuir?
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 Dunsmuir?
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 Dunsmuir?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Dunsmuir Municipal Code Chapter 17.116 (Ord. No. 575, § I(Exh. A), 6-29-2023)
- Dunsmuir Municipal Code § 17.116.030(B)
- Dunsmuir Municipal Code § 17.116.030(E)(1)
- Dunsmuir Municipal Code § 17.116.030(E)(2)
- Dunsmuir Municipal Code § 17.116.030(E)(3)
- Dunsmuir Municipal Code § 17.116.030(E)(13)
- Dunsmuir Municipal Code § 17.116.030(E)(13)(c)
- Dunsmuir Municipal Code § 17.116.030(C), § 17.116.040(C)
- Dunsmuir Municipal Code § 17.116.040(I)
- Dunsmuir Municipal Code § 17.116.030(F)
- Dunsmuir Municipal Code § 17.116.030(J)
- Dunsmuir Municipal Code § 17.116.030(K)
- 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 § 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 Dunsmuir'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 Dunsmuir Planning before relying on it.
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