California ADU rules · Alameda County
Can I Build an ADU in Fremont?
Yes — you can build an ADU in Fremont. California's statewide ADU law requires every city, including Fremont, 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
CA state lawConversion ADUs (≥1, up to 25% of units) + up to 8 detached
Conversions of non-livable space (at least 1, or up to 25% of existing units) plus up to 8 detached ADUs on a lot with existing multifamily — never exceeding the number of existing units. JADUs are single-family only.
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
Fremont explicitly caps a new detached ADU at 1,200 sq ft (its local maximum, matching the state default). A 'statewide-exemption' ADU may instead be built at up to 800 sq ft with 4-ft setbacks regardless of other standards.
Max attached ADU size
Local ruleUp to 1,000 sq ft for a new attached ADU (local cap); state law still guarantees ≥850 sq ft, or ≥1,000 sq ft for 2+ bedrooms
Fremont sets a flat 1,000 sq ft local cap for new attached ADUs (rather than the state's 50%-of-primary formula). A 'statewide-exemption' attached ADU may be built at up to 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 rule16 ft
Detached ADUs follow the 16-ft base (18 ft near transit / for multistory MF lots) + 2 ft for roof pitch. Fremont allows an ATTACHED ADU up to 30 ft (or the zone's primary-dwelling height limit, whichever is lower), not more than 2 stories — more generous than the state's 25-ft attached figure.
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
Fremont requires no additional off-street parking for any ADU, and no replacement parking when a garage/carport is demolished or converted — broader than the state's case-by-case exemptions.
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
CA state lawOnly for a JADU
No owner-occupancy requirement for ADUs (the prior sunset was removed). A JADU may require owner-occupancy, principally where it shares sanitation with the main house.
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.
Fremont-specific factors that can change the answer
State law sets the floor, but these local conditions often decide whether a specific parcel works.
California Register historic resources
An ADU involving exterior modifications to a structure listed in the California Register of Historical Resources must conform to the Secretary of the Interior's Standards for the Treatment of Historic Properties.
Fremont's § 18.190.005 specifies its own size envelope — a 1,200 sq ft detached cap, a flat 1,000 sq ft attached cap, and an unusually tall 30-ft height limit for attached ADUs — and requires zero off-street parking for any ADU. JADUs (≤500 sq ft, within the single-family residence) carry the standard owner-occupancy requirement.
Frequently asked questions
Can I build an ADU in Fremont?
Yes. California's statewide ADU law requires Fremont 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 Fremont?
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 Fremont?
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 Fremont?
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 Fremont?
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 Fremont?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Fremont Mun. Code § 18.190.005 (Ord. 01-2025)
- FMC § 18.190.005(c)(4)(B)(ii)
- FMC § 18.190.005(c)(4)(B)(i)
- FMC § 18.190.005(c)(5)
- FMC § 18.190.005(c)(14)
- FMC § 18.190.005
- 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 § 66314 (local ordinance standards)
- Cal. Gov. Code § 66315 (owner-occupancy)
- 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 Fremont'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 Fremont Planning before relying on it.
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