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Toolkit for Accessory Dwelling Units

This workbook was created as a resource to help residents of Milpitas build a second unit. It provides a detailed, step-by-step approach to the entire project—from getting started to assisting homeowners in the process of building a second unit. The workbook was designed to provide useful information and reduce the uncertainty in what can feel like a complicated process.


ADU Mondays

The City of Milpitas is launching an ADU Monday Program to provide a simple and easy pathway to encourage Milpitas residents to explore the idea of developing an ADU on their property.  The program provides a complimentary consultation service to help answer your questions regarding ADUs.  Please note that this is not an express plan review service. Should you decide to submit a permit application to develop an ADU, City procedures and charges in accordance with the City’s fee schedule will apply.

An online appointment platform has been created where you will be able to schedule a virtual meeting with members from Building Safety, Planning, and Land Development to explore the development of an ADU.

Please click below to answer a few brief questions and schedule your ADU Monday appointment.  We look forward to assisting you.

Learn more about Accessory Dwelling Units — also called ADUs, secondary units, or granny flats — are small living units, including a kitchen and bathroom, on properties zoned residential with a single-family home, duplex home, or multifamily building in place. Junior Accessory Dwelling Units (JADUs) are small (less than 500 square feet) that must be converting existing square footage of a single-family home. ADU  & JADU information and requirements can be found on the ADU Zoning Ordinance.

The Building Safety and Housing Department launched the Accessory Dwelling Unit (ADU) Incentive Program and the Safe ADU Legalization Program that feature the waiver of all City permitting fees for construction of a new ADU and legalization of a non-permitted ADU or JADU.

If you would like to e-mail your questions regarding ADUs, please send them to

FAQs on ADUs


What's an ADU?

ADUs are known by many names — including accessory dwelling unit, second unit, in-law unit, granny flat, casita, and backyard home. But, no matter what you call them, these are homes located on the same piece of property as another home. They provide a complete and permanent home for at least one person.

What are the different types of ADUs?

Conversion ADUs are built by converting part of a single-family home (e.g., an attic or basement) or all or part of an accessory building (e.g., garage, shed, pool house) into a new home. In apartment or condo buildings, Conversion ADUs are made by converting non-living spaces (e.g., storage rooms, boiler rooms, passageways, attics, basements, and garages).

Junior ADUs (JADU) are a type of Conversion ADU that are no more than 500 sq. ft. and built within a single-family home. JADUs can have an efficiency kitchen and share a bathroom with the main home.

Attached ADUs are constructed, at least in part, by adding on to a single-family home.

Detached ADUs are free-standing buildings that are unattached to the single-family home or apartment/condo building.

Where can I build an ADU?

An ADU may be established on any lot in any district that allows single-family or multi-family dwelling residential uses. A JADU may be established on any lot in any district that allows single-family residential use

Regulations depend on whether ADU is located within Hillside Combining District or non-Hillside Combining District

What are the benefits of ADUs?

For a homeowner, an ADU can bring many benefits, including:

  • Extra rental income to help pay the mortgage, save for retirement, or build a financial safety net.
  • An increase in a property’s value.
  • A way to downsize without moving away from one’s community.
  • A nearby, yet private, home for family members, friends, or caretake


What are the general standards?


Two stories, except on the west side of Hillside Crestline, which is one story.

Lot Size:

No minimum

Maximum ADU Floor Area:

Attached: Single-family, cannot exceed 50% of existing living area or 850 sq. ft. max for a studio or one-bedroom unit and 1,000 square feet for a two-bedroom unit,  whichever is smaller; Hillside combining districts, 1,200 sq.ft.

Detached: In non-Hillside, depends on whether sharing lot with single or two family dwelling.  Two-family, cannot exceed 50% of existing living area of the smaller of the two units.

Junior: Max 500 sq. ft.


2 Bedroom max.


One kitchen max., require separate kitchen facilities (permanent range, counters, refrigerator, sink).

Junior: Efficiency kitchen included


The entrance to an attached ADU or JADU shall be located on a side or rear building façade, not facing a public right-of-way.
The ADU and primary dwelling must use the same driveway to access the street unless otherwise required for fire-apparatus access, as determined by the fire authority.

ADU Parking Requirements & Exemptions

For the ADU, one parking space is required unless the property qualifies for an exemption under State law. Many ADUs qualify for an exemption.


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

  1. The ADU is located within 0.5 miles of a public bus stop or rail station (see, and the path of travel is publicly accessible.
  2. The ADU is part of or within the primary residence or existing accessory building.
  3. 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.
  4. 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.
  5. The ADU is located within a historic district listed in the City’s (Milpitas does not have any)


As of June 16, 2020, in alignment with new state laws, if a garage is converted to an ADU, the parking spaces no longer must be replaced.

What are setbacks?

A setback is a distance a building needs to be located away from the property lines.

No minimum setback requirement applies to newly constructed ADUs built in the same location and with the same dimensions as a previously existing structure. For all other ADUs, a minimum setback of 4’ from the side and rear lot lines is required.

Limited Detached on Single-family Lot: 4’ side- and rear-yard setbacks
Limited Detached on Multi-family Lot: 4’ side- and rear-yard setbacks

Except for Attached ADUs in the R1-H zoning district, the minimum front yard setback requirement for an attached ADU is 8 feet. In the R1-H zoning district, the minimum front yard setback for attached ADUs must be a minimum of 25 feet when the slop is less than 16%, otherwise, the minimum front yard setback must be 40 feet.

How is building height measured?

Generally, the height of a building is the vertical distance between the top of the roof and the ground below. Special rules may apply if your property is sloped.

Single-story attached or detached ADU: 16’ above grade.

Two-story attached or detached ADU: 28’ above grade.

ii. For properties located Hillside Combining District, an attached or detached ADU on the west side of the crestline may not exceed a height of 17 feet in height and one story from the lowest finished grade to the highest ridgeline of the building. On the east side of the crestline, a detached or attached ADU may not exceed a height of 27 feet and two stories from the lowest finished grade to the highest ridgeline of the building.

What does rear yard coverage mean?

In Milpitas, only a portion of a property’s backyard may be covered by buildings and other structures. ADUs footprint is exempt from this requirement, however, other accessory structures are not.

Note: Fire Department regulations should be assessed on a project by project basis.


Fees for ADUs

The size of your ADU will determine your building permit fees.  Please see Accessory Dwelling Units (ADUs) Permit Fee Estimate for detailed building permit fees information.

In addition to the building permit fees, other fees may apply.

  • Minor Site Development Permit review will be required if your ADU is not eligible for a limited review or requesting to deviate from design standards, which involves the payment of a fee.
  • A school impact fee will also be required if your ADU project proposes an additional floor area of 750 sq. ft or more.
  • If your project involves tree removal, a Tree Removal Permit will be required, which involves paying a fee.

Utility Connections

For instance, if you construct your ADU with a new single-family home, no separate utility connection between the ADU and the utility will be required, except as described in Section XI-10-13.08(H)(a) would the ADU be subject to a connection fee and capacity charge. That being said, if your ADU is eligible for limited review, it will not be required to have a new or separate utility connection directly between the ADU and the utility, and it will not be subject to a connection fee or capacity charge. You will also need to outfit your ADU with fire sprinklers if they are required in your primary residence. If your property relies on a septic system, additional testing may be required.



An ADU or JADU can always be rented long-term. A long-term rental is defined as a rental period that is 31 days or greater. Airbnb or other short-term rentals less than 30 days are restricted for ADUs and JADUs.

Can the ADU be sold separately from the primary residence?

Sale Prohibited. No ADU or JADU may be sold or otherwise conveyed separately from the lot and the primary dwelling (in the case of a single-family lot) or from the lot and all of the dwellings (in the case of a multi-family lot).

Does the property owner need to live on the property where the ADU is located?

Owner occupancy requires that the homeowner either lives 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 an 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.