California ADU rules · Marin County
Can I Build an ADU in Belvedere?
Yes — you can build an ADU in Belvedere. California's statewide ADU law requires every city, including Belvedere, 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); detached: up to 2 on proposed multifamily, up to 8 on existing multifamily, not to exceed number of existing units
Detached ADUs on multifamily lots capped at 2 for proposed multifamily and 8 for existing multifamily, not to exceed number of existing 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 rule1,000 sq ft
Standard detached ADU max is 850 sq ft (studio/1-bed) or 1,000 sq ft (2+ beds); up to 1,200 sq ft if deed-restricted affordable.
Max attached ADU size
Local rule850 sq ft (studio/1-bed); up to 1,000 sq ft or 50% of primary, whichever is less, if deed-restricted affordable
Standard attached ADU max is 850 sq ft; size bonus for deed-restricted affordable units.
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; up to 25 ft on parcels with ≥30% slope. Attached ADU: up to 25 ft or primary dwelling height limit.
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 ruleNone required
No fixed minimum; must meet fire/safety separation.
Parking
Parking required
Local ruleNone
No additional parking required for ADUs that meet development standards; 1 space only if no exemption applies.
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 required for ADUs; replacement required for JADUs if garage is converted.
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 for JADUs only.
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.
Belvedere-specific factors that can change the answer
State law sets the floor, but these local conditions often decide whether a specific parcel works.
Very High Fire Hazard Severity Zone (VHFHSZ)
ADUs must comply with all local and state building/fire codes; no additional local restrictions.
Hillside parcels (≥30% slope)
Detached ADU height may be increased up to 25 ft as needed for 9 ft interior ceiling.
Historic Districts
No parking required for ADUs in historic districts; demolition notice/placard required only in architecturally/historically significant districts.
Belvedere caps standard detached ADUs at 1,000 sq ft (2+ beds) and attached ADUs at 850 sq ft, with size bonuses for deed-restricted affordable units. Detached ADU height may reach 25 ft on steep hillside lots.
Frequently asked questions
Can I build an ADU in Belvedere?
Yes. California's statewide ADU law requires Belvedere 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 Belvedere?
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 Belvedere?
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 Belvedere?
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 Belvedere?
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 Belvedere?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Belvedere Municipal Code Chapter 19.79 (Ord. 2025-11, eff. Jan 12, 2026)
- BMC §19.79.030(B)
- BMC §19.79.040(A)(1), §19.79.070(A)
- BMC §19.79.040(B)(1), §19.79.070(A)(2)
- BMC §19.79.040(A)(4), (B)(3), §19.79.080(J)(3)
- BMC §19.79.040(A)(3)
- BMC §19.79.050(A)
- BMC §19.79.050(A)(4), §19.79.080(M)
- BMC §19.79.080(I)
- BMC §19.79.040, §19.79.050, §19.79.080
- BMC §19.79.040(A)(4)
- BMC §19.79.050(A), §19.79.080
- 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 Belvedere'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 Belvedere Planning before relying on it.
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