Introduction to Accessory Dwelling Units

An accessory dwelling unit commonly called a granny flat or in-law suite must exist on a lot that’s zoned single-family. It has its own entrance, separate from the primary house, as well as a kitchen, bathroom and living space. These units can be rented, year-round, and add a lot of value to a property.

Accessory dwelling units take different structural forms. They can be garage conversions, stand-alone units, attic or basement conversions, or be attached to the main house.

ADU Regualtions



Fremont’s previous legislation:

Accessory dwelling units (ADUs) shall be allowed in: any R-1 (single-family residential) district, those portions of planned districts allowing single-family dwellings, single-family dwellings located within an R-2 (two-family and duplex residential) district, certain smaller lots within R-3 (multifamily residential) and R-G (garden residential) districts, and the general, hill, hill face and hillside open space districts wherein a single-family residence has been authorized. All ADUs shall be subject to the provisions of this section. In the event of a conflict between the provisions of this section and another section of the Fremont Municipal Code, the provisions of this section shall prevail.

With the new 2020 laws in effect, an ADU is allowed on a lot that is zoned to allow single-family or multifamily dwelling residential use and includes a proposed or existing dwelling.If you aren’t sure what zone your property is in, Maxable can tell you!

Lot size

Thanks to new ADU legislation there are no longer minimum lot size.

Min/Max Building Sizes

Previously, Fremont's regulations were as follows:

JADU's cannot exceed 500 square feet.

ADU's may not be smaller than 150 square feet.

The maximum floor area of an ADU is limited to no more than 50% of the habitable floor area of the main unit, or the following figures, whichever is less:

Parcel Size: ...................................Maximum Floor Area of ADU (sq. ft.):
Less than 5,000 ........................... 500
5,000 – 7,999 ...............................700
8,000 – 9,999 ................................800
10,000 – 19,999 ...........................900
20,000 – 39,999 ...........................1,050
40,000+ ........................................1,200

For example, if your lot size is 5,000 square feet and your primary dwelling is 1,200 square feet, your ADU may be up to 600 square feet.

Now, however, since the 2020 legislation went into effect they must allow an 850 square foot 1-bedroom or a 1,000 sq foot two bedroom ADU regardless of size of the principal dwelling unit. "

Height Restrictions

Previously, Fremont's regulations were as follows:

ADU's cannot exceed the building height limits that apply to the primary dwelling.

With the new 2020 laws now in effect, the height of an ADU is allowable up to 16 feet.


No parking is required for an ADU that meets any of the following criteria:

The ADU is located within .5 mile of a public bus stop or rail station, and the path of travel is publicly accessible.

The ADU is part of or within the primary residence or existing accessory building.

The ADU is on a street that requires on-street parking permits, but the permit has not been offered to the occupant of the ADU.

The ADU is located within one block of where a motor vehicle provides hourly and daily service as part of a regional fleet operated by a public agency or publicly-leased motor-vehicle-sharing organization.

The ADU is located within a historic district listed in the City’s Historic Resources Inventory.
If you convert your garage the parking spaces are no longer required to be replaced. This is in alignment with the new state laws.

If you are not sure if you meet any of these waiver requirements, contact Maxable today and we can check!

If parking is required, it can be provided through any of the following ways:

  • Conventional garages or carports
  • Uncovered paved areas, such as extended driveways
  • Tandem parking in a garage or driveway
  • Parking locations on other locations on the property (including within the setbacks), unless these areas are deemed unsafe

No off-street parking is required for JADU’s.


It is required that an ADU maintains a 4-foot minimum rear and side setback

Owner Occupancy

Owner occupancy requires that the homeowner either live in the ADU or in the primary dwelling. Owner occupancy has been removed in all jurisdictions in California until the year 2025. Any homeowner who builds and ADU from 2020-2025 will forever be grandfathered into no owner occupancy requirement even if the legislation changes to require owner occupancy in the future.


An ADU can always be rented long-term. A long-term rental is defined as a rental period that is 30 days or greater. Often Airbnb, or other short-term rentals are restricted for ADUs. Check your local planning department to find out if a short-term rental in your ADU would be legal.

How to Evaluate ROI

People often underestimate the cost to build a small unit. There are a lot of fixed costs and the expensive square footage, like a kitchen and bathroom, are not offset by large cheaper square footage (for example, large living rooms, hallways, and multiple bedrooms).

With that being said, building an accessory dwelling unit, especially if you intend to keep the property for a few years, represents an enormously beneficial opportunity to maximize your property.

By constructing an accessory dwelling unit you are adding additional square footage to the property. So if you can build a unit for $275 a square foot, but the average value of homes in your neighborhood are worth $400 a square foot you are gaining instant equity through the project. Plus, you also now have the added benefit of a flexible space that can be rented or used for family.

Property Value (avg value per sq ft)


Construction Costs (avg cost per sq ft)

$300 per square foot (Cost will vary depending on the size of the structure. The smaller you build the higher your cost per square foot will be)

Equity Gained through project

$491-300= $191 (Meaning you are gaining $191 in property value for every square foot built)

Additional notes!/html/Fremont18/Fremont18190.html

Updated on: 1/21/20

Ready to dive in? Check out our consultation services or start with a preliminary phone call.

Fremont ADU Regulations