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Fremont ADUs

Everything about building Accessory Dwelling Units in Fremont, CA

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The city government of Fremont has updated its local zoning codes to comply with the State ADU mandate.
The California Building Code (CBC) 2019 is adopted.

Last Updated 10/13/20


City Hint: The city permitted a total of 64 ADU projects in the past year of 2019, which makes it above average for ADU production compared to other cities statewide.

Number of ADUs allowed:

Multi-Family Lots: The number of SADUs permitted through the conversion of existing floor area is limited to 25% of the number of existing dwelling units. Additionally, up to two detached SADUs can be constructed on a lot with a multi-family residence

Single-Family Lots:
On lots with one single family residence, one junior accessory dwelling unit (JADU) and one
standard accessory dwelling unit (SADU) are permitted

Types of ADUs allowed:

Detached ADU, Attached ADU, Junior ADU are allowed. Accessory Dwelling Unit (ADU)s may be new construction or converted from existing space. Junior Accessory Dwelling Units must be converted from existing space.

Lot size:

Accessory Dwelling Unit projects on single family or multi-family residential parcels will not be subject to the minimum lot size of the underlying local zoning code or by special ordinance. ~ AB-68

ADU size:

• The total floor area of a SADU shall be no less than 150 square feet.
• Attached SADUs are limited in size to 50% of the floor area of the primary residence or 800 square feet, whichever is greater.
• Detached SADUs are limited to 1,200 square feet in size.
• For SADUs 800 square feet or less, any underlying first floor lot coverage, floor area ratio, or open space requirement may be modified to the extent necessary to allow for the construction of the SADU. Any second story area limitations are still applicable.

The maximum size of a detached SADU on a multifamily property is 850 square feet for a studio or and one bedroom unit, and 1000 square feet for a two or more bedroom unit.


Attached and detached SADUs (Standard ADUs) can be located as close as four feet from the rear, interior side, and exterior side (i.e. street-side) property lines. SADUs must follow the front yard setbacks as provided in the applicable zoning ordinance.

A garage or accessory structure can be converted into an ADU without regard to setbacks, provided that the setbacks are sufficient for fire and life safety


• One parking space is required for an SADU, except that no parking is required where the ADU meets any of the following criteria:
o The SADU is a studio (no bedrooms)
o The SADU is located within ½ mile (measured by actual walking distance) of public transit, including BART stations, the ACE Station in Centerville, and bus stops.
o The SADU is located within the Mission San Jose or Bryant Street Conservation Areas, or on a property that includes a historic register resource or potential historic register resource.
o The SADU is located entirely within the existing principal residence and adds no habitable floor space to the property.
o The SADU is located in an area where on-street parking permits are required, but are not offered to the occupants of the SADU.
o The SADU is located within one block of a designated parking area for one or more car share vehicles available to the general public by subscription.
Note: If requesting a waiver from parking requirements, the applicant must submit evidence that the property meets one of the criteria above.
Where a parking space is required, it may be provided through any of the following methods:
• Conventional garages or carports
• Uncovered paved areas such as extended driveways
• Tandem parking in a garage or driveway
• Parking on other locations on the property (including within the setbacks), unless specific findings are made that parking in these areas is not feasible based on life safety conditions.

• Replacement parking is not required if the ADU involves the demolition, conversion, or partial conversion of a garage or carport

Fire Safety:

If a detached structure, the ADU must be separated from other habitable structures on the lot by at least 10 feet. This may be reduced to eight feet if one structure is equipped with fire sprinklers or six feet if both structures are equipped with fire sprinklers. Other exceptions may apply.

• The separation between a detached SADU and another structure on the same lot is only that as required by Building and Fire code.

SADUs shall not be held to a higher standard than the principal residence for fire sprinklers. Fire sprinklers shall only be required if they would be required for an equivalent addition or modification of space on a residential property that was not associated with a SADU.
A smoke alarm and carbon monoxide detector is required.

Shape, materials and style:

ADUs shall incorporate architectural features, building materials and colors that are compatible with the principal residence.
1. Outside stairways to the ADU shall not be in the front of the principal residence.
2. A continuous paved pathway from the street to the front door of the ADU (called a “passageway”) may be added, but is not required.


Attached SADUs may not exceed the building height limits applicable to the principal residence. Detached SADUs are limited to 16 feet in height.

Design review:

An application for an ADU that meets the applicable standards in the Fremont Municipal Code (FMC) is subject only to ministerial review and approval. This means that the application may be approved by staff and no public hearing is required. Where design review requirements are applicable (for example, for an addition or a new detached structure), a Ministerial design review Permit is required.

Number of Bedrooms:

Not specified by State Standards.


A property owner may rent out both a SADU and the primary residence if the SADU was permitted between January 1, 2020 and December 31, 2024. SADUs permitted prior to this period are still required to have the owner live in either the SADU or the primary residence. Owner occupancy is also still required for all JADUs regardless of permitting date.
• An ADU may not be rented for a term of less than 30 days.
• A deed restriction must be filed with Alameda County prohibiting the sale of the ADU as a separate residence, and verifying that the unit complies with the City’s requirements.

Utility connections:

Permits from the Alameda County Water District (ACWD) and Union Sanitary District (USD) may also be required. A fee is required for the building permit and may be required for other permits.


Accessory Dwelling Units (ADUs—also known as “secondary dwelling units” or in-law apartments) are attached or detached residential dwelling units that are subordinate to a principal residence on the same lot and that provide complete independent living facilities for one or more persons. ADUs include permanent provisions for living, sleeping, eating, cooking, and sanitation.

Historic Requirements:

On lots that have been deemed eligible or formally listed on the National Register of Historic Places, the California Register of Historical Resources, or any adopted local list of historic resources, architectural approval must be granted by the Historical Architectural Review Board (HARB).


ADUs do not count toward the density requirements in the General Plan or zoning regulations.

Allowed Zones:

*** Beginning in 2020, according to state law, all residential zoning districts, including single-family and multi-family, are allowed to build Accessory Dwelling Units. ***

ADUs are not permitted in duplexes, triplexes, and other buildings with more than one principal residence.


Note: ADUs are not allowed on “constrained” land, where development capacity is limited because of conditions determined to be detrimental to public health, safety and welfare, such as soil instability or severe slopes. In such areas, ADUs may be located only within the area of the lot allowed for the principal residence.

Residential Building Code:

The California Building Code (CBC) 2019 is adopted.

Fremont City Planning Offices

Community Development Department

39550 Liberty St. Fremont, CA 94538 Fremont, CA 94538

Read Fremont Housing Market Update

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Detached ADU - Completed in 2020
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Costs / ROI



* upon completion of ADU


* based on local average price per sqft


* estimated by location


* 30 years / 5% interest rate / 20% down payment


Size: 500 sqft


Appreciation Estimate = (Base Value: $) / (Home's Living Space: sqft) * (ADU's Living Space: sqft)

Rental Estimate = (Rent Per Sqft: $3.96) * (ADU's Living Space: sqft)

Check your property's zoning, browse designs & get contractor estimates for your ADU project:

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