Accessory Dwelling Units

What is an ADU?

Accessory dwelling units (ADUs), also called second units, granny units, casitas, or cottages, are allowed in all residential zoning districts where single family residences are allowed to promote the goal of affordable housing within the City. The Accessory Dwelling Units Ordinance has the regulations and guidelines for this type of development.

Benefits of ADUs

ADUs have many benefits including being:

an affordable type of home to construct in California because they do not require paying for land, major new infrastructure, structured parking, or elevators and even impact fees, in some cases.
a source of income for homeowners.
cost-effective wood frame construction, which is significantly less costly than homes in new multifamily infill buildings.
spacious enough to allow as much living space as many newly-built apartments and condominiums, and well-suited for couples, small families, friends, young people, and seniors.
a means to allow homeowners the flexibility to share independent living areas with extended family members or caregivers, which additionally allow seniors to age in place when they require more care.

Building an ADU

The Cupertino Planning Department will help ensure your project proposal complies with the zoning code and development standards. Feel free to email preliminary plans/queries to planning@cupertino.gov.

A building permit is required to build an ADU. Visit the Cupertino Building Permit Center for hours of operation and contact information or email building@cupertino.gov.

Please see our Accessory Dwelling Unit Information Sheet(PDF, 511KB) and Steps to A Completed ADU Handout(PDF, 155KB) for more information on how to plan and build your ADU.

Please visit City's ADU development standards.

Floor Area for purposes of ADUs

ADUs ≤ 800 s.f. (living area, excluding decks, etc.) are not limited by lot coverage, FAR, and open space requirements
ADUs > 800 s.f. are limited by lot coverage, FAR, and open space requirements
ADUs in multi-family developments are not limited by lot coverage, FAR, or open space requirements
Internal Conversions in multi-family dwellings must be created out of space that is not used as livable space (i.e. attic, basement, storage room)

What is a JADU?

An ADU ≤500 s.f.
Contained entirely within an existing or proposed home (not a garage)
Must fit within the allowed 45% Floor Area Ratio
Must have an efficiency kitchen at the minimum
Bathroom may be shared or independent from principal unit
Converted out of habitable living space

ADU Specifications

An Accessory Dwelling Unit may:

Be exempt from Floor Area Ratio and Lot Coverage limitations, if ≤ 800 s.f.
Have a separate address
Be rented
Be located as close at 4 ft from the rear and side property lines, if ≤ 800 s.f.
NOT be sold separately from the principal dwelling unit
NOT have an interior connection with the primary dwelling unit except if it is a JADU with a shared bathroom
NOT have to pay park, storm drain and school impact fees, if < 750 s.f.

FAQs

How many ADUs can I build, at most, on my property?

For single Family property, you can construct a streamlined detached ADU (≤ 800 sq. ft.) and a JADU for a total of two ADUs. Note that a JADU cannot be combined with either an attached ADU, or a detached ADU that is greater than 800 sq. ft. For multi-family property, you can construct up to two detached ADUs and convert non-habitable spaces to construct up to 25% of this number of existing units (minimum one) as ADUs.

Is there a limit to the number of bedrooms allowed in an ADU?

There is no limit on the number of bedrooms in an ADU. However, for single family property, there are size restrictions depending on the number of bedrooms proposed. For a studio or one-bedroom unit, the maximum size allowable is 850 sq. ft. while for any ADU with two or more bedrooms, the maximum allowable size is 1,000 sq. ft.

May I sell or rent my ADU?

An ADU may be rented, but not sold, separately from the principal dwelling unit. However, ADUs, including JADUs, may not be used for short-term rental activity. For JADUs, the owner must occupy either the principal dwelling unit or the JADU. Additionally, the owner shall record a deed restriction prohibiting the sale of the JADU separate from the principal dwelling unit and restricting the size and attributes of the JADU to conform with JADU regulations.

Can I have a door or any connection between my attached ADU and my primary dwelling unit?

No internal access is allowed except for a JADU that has a shared bathroom with the principal dwelling unit on property with single family uses. All other ADU’s must be completely separated from the principal dwelling unit or other units (in a multi-family development).

Can I have a two-story ADU?

A two-story ADU is allowed if you are converting a portion of existing second story space into an ADU.

Is an ADU required to have its own address?

A detached ADU is required to have its own address. All other types of ADUs may have their own address but are not required to.

Can I propose a JADU and an attached ADU with my brand new single family home?

No. For single Family property, you can construct a streamlined detached ADU (≤ 800 sq. ft.) and a JADU for a total of two ADUs. Note that a JADU cannot be combined with either an attached ADU, or a detached ADU that is greater than 800 sq. ft.

Is there a replacement parking requirement for converting a garage into an ADU?

You do not need to provide replacement parking when converting a garage into an ADU.

Can I convert my existing 2-car garage to be a 300 sq. ft. ADU and use the balance of the sq. ft. for my principal dwelling unit?

Existing garages can be converted into an ADU, but no portion of the existing garage may be converted for use as livable/usable space by the principal dwelling unit.

Can I convert my existing attached garage into a JADU?

A JADU is created by converting space within the walls of the principal dwelling unit. Therefore, the garage conversion would have to be the property’s only ADU and could not be considered a JADU. In this situation, for single family property, you could not have any other type of ADU (including a JADU).

Can an ADU have its own garage and/or covered patio?

Yes, as long as the garage and/or covered patio proposed meet(s) the necessary size, height, and setback regulations; as well as, the Floor Area Ratio and lot coverage restrictions for the property.

Can I absorb the space of an ADU built under the relaxed state regulations into the principal dwelling unit?

No. The relaxed floor area and lot coverage standards are to allow additional housing units to become available, not to allow larger principal dwelling units.

Do I have to pay impact fees?

ADUs < 750 sq. ft. in size will not incur park, storm drain, or school impact fees. ADUs larger than this size will still incur these impact fees. Please contact the Public Works Department at (408)-777-3354 or Cupertino Union School District at 408.252.3000 ext. 61-373 for more information.

Will my property taxes increase if I build an ADU?

Yes. The County Assessor appraises all new construction and remodels, including ADUs, at fair market value. Please visit www.sccassessor.org for more information.

Do I need a separate water and/or electric meter for my ADU?

Please contact your water provider and/or PG&E to determine whether these are needed.

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