California ADU rules · Humboldt County
Can I Build an ADU in Blue Lake?
Yes — you can build an ADU in Blue Lake. California's statewide ADU law requires every city, including Blue Lake, 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
ADUs require a special use permit (discretionary approval), not ministerial/by-right.
Units on a single-family lot
Local rule1 ADU
Only one ADU permitted per parcel; JADUs not addressed in local code.
Units on a multifamily lot
Local rulenot permitted
ADUs are not permitted on lots with two or more dwelling units.
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 rule900 sq ft
Local maximums: 640–900 sq ft by lot size, but state minimums override for most ADUs.
Max attached ADU size
Local rule30% of primary or local detached max, whichever is less
Local rule is 30% of primary or detached max, but state minimums override if less than 850/1,000 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
Local rule20–25 ft by lot size
Local front setback applies (20–25 ft), but cannot preclude an 800 sq ft ADU.
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
One off-street parking space required for ADU in addition to primary unit parking; 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
Local ruleMinisterial (by right)
California Gov. Code § 66317 requires ministerial, by-right approval of a qualifying ADU; any local discretionary or conditional-use process is preempted for ADUs meeting objective standards.
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
Local code recites an owner-occupancy requirement, but California Gov. Code § 66315 bars owner-occupancy requirements for ADUs — enforceable for JADUs only. Verify the JADU covenant with the city.
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 ruleSpecial use permit, Building permit
Special use permit required prior to building permit.
Blue Lake-specific factors that can change the answer
State law sets the floor, but these local conditions often decide whether a specific parcel works.
Minimum lot size
Local code requires 6,000 sq ft lot, 50 ft width, 80 ft depth for ADUs, but this is not enforceable under state law.
No ADUs on manufactured home lots
ADUs are not permitted on lots with manufactured homes or as manufactured homes.
Blue Lake requires a discretionary special use permit for all ADUs and limits ADUs to one per single-family lot, with no ADUs allowed on multifamily lots. Owner-occupancy is required for either the primary or accessory unit, and local size/setback rules are generally overridden by state law.
Frequently asked questions
Can I build an ADU in Blue Lake?
Yes. California's statewide ADU law requires Blue Lake 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 Blue Lake?
A detached ADU of at least 900 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 Blue Lake?
Side and rear setbacks are limited to 4 ft. 20–25 ft by lot size.
Is parking required for an ADU in Blue Lake?
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 Blue Lake?
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 Blue Lake?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Blue Lake Municipal Code § 17.24.270 (Ord. 544B, 11/26/2024)
- § 17.24.270(B), (J)
- § 17.24.270(C)(1)
- § 17.24.270(C)(4)
- § 17.24.270(C)(3), Table 1
- § 17.24.270(C)(6)
- § 17.24.270(C)(11)
- § 17.24.270(C)(10)
- § 17.24.270(C)(14)
- Cal. Gov. Code §§ 66310–66342 (ADU Law)
- HCD 2025 Accessory Dwelling Unit Handbook
- 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 § 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 2026-06-25. This is an AI-assisted summary of Blue Lake'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 Blue Lake Planning before relying on it.
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