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Cupertino City Zoning Code

CHAPTER 19

112: ACCESSORY DWELLING UNITS

19.112.010 Purpose; Incorporation by Reference; Consistency with State Law.

The purpose of this chapter is to promote the goal of affordable housing within the City through provision of additional housing in certain residential, agricultural residential, and mixed‐use zoning districts in a manner which minimizes adverse impacts of accessory dwelling units on neighborhoods. Unless otherwise defined in this Title, all terms used in this Chapter shall be defined and interpreted in accordance with Government Code Sections 66310-66342. In the event of a conflict between this Chapter and the requirements of State law, the requirements of State law, including the requirements of Government Code Sections 66310-66342, shall prevail.

(Ord. 20-2199, § 5 (part), 2020; Ord. 16-2159, § 8 (part), 2016; Ord. 2085, § 2 (part), 2011; Ord. 1601, Exh. A (part), 1992; Ord. 23-2254, Att. A (part), 2023; Ord. 25-2274, Att. A (§ 1), 2025; Ord. 25-2274, Att. A (§ 1), 2025)


19.112.020 Accessory Dwelling Unit Regulations.

Notwithstanding any provision of this title to the contrary:

  1. Accessory dwelling units are permitted on lots within any residential or mixed-use residential zoning district. The lot must have an existing single family dwelling unit or if zoned multi-family or mixed use residential, at least one residential unit. If the lot is vacant, an accessory dwelling unit may only be proposed in conjunction with the development of at least one residential unit. Notwithstanding the underlying zoning, an accessory dwelling unit developed pursuant to this chapter does not cause the lot upon which it is located to exceed its maximum allowable density on the lot.
  2. Accessory dwelling units, except those pursuant to Government Code Section 66323, must comply with the site development regulations and guideline specified in those zoning districts for dwelling units, including but not limited to: lot coverage; floor area ratio; height; setbacks; landscape; the regulations contained in this chapter; Chapter 19.100, Accessory Structures/Buildings; and Chapter 19.124, Parking; except as those standards are modified by this chapter.
  3. No impact fees, as defined in Government Code Section 6324(c)(2), shall be imposed on any accessory dwelling unit or junior accessory dwelling unit with a gross floor area of less than 750 square feet. Impact fees imposed on accessory dwelling units greater than or equal to 750 feet shall be charged proportionally in relation to the square footage of the primary dwelling unit in compliance with Government Code Section 6324(c)(1).
  4. Accessory dwelling units may be rented separately from the single-family dwelling or multi-family dwelling structure but may not be sold or otherwise conveyed separately from the other dwellings on the lot, except pursuant to Government Code Section 6340 – 66342. Any accessory dwelling unit, including a Junior Accessory Dwelling Unit (JADU), shall not be used as a rental for a term less than 30 days.
  5. For JADUs, either the single-family residence or JADU must be owner-occupied, unless the owner is a governmental agency, land trust, or housing organization. Further, the owner shall record a deed restriction, expressly enforceable against future purchasers, containing the following: (a) a prohibition on the sale of the JADU separate from the single-family residence, and (b) a restriction on the size and attributes of the JADU to conform to this section.
  6. A local agency shall not issue a certificate of occupancy for an accessory dwelling unit before the local agency issues a certificate of occupancy for the primary dwelling.

(Ord. 20-2199, § 5 (part), 2020; Ord. 17-2170, § 3, 2017; Ord. 16-2159, § 8 (part), 2016; Ord. 2085, § 2 (part), 2011; Ord. 1901, (part), 2002; Ord. 1601, Exh. A (part), 1992; Ord. 23-2254, Att. A (part), 2023; Ord. 25-2274, Att. A (§ 1), 2025; Ord. 25-2274, Att. A (§ 1), 2025)


19.112.030 Site Development Regulations for Streamlined Accessory Dwelling Units & Junior Accessory Dwelling Units.

Pursuant to California Government Code Section 66323, the City shall approve the following streamlined accessory dwelling units if the specified development standards and use restrictions are met, as identified in:

  1. Table 19.112.030A for single-family residential uses and
  2. Table 19.112.030B for multi-family residential uses.


19.112.040 Site Development Regulations for Non-Streamlined Accessory Dwelling Units.

  1. This section shall govern applications for ADUs and JADUs that do not qualify for approval under Section 19.112.030 or Government Code section 66323 and for which the city may impose local standards pursuant to Government Code section 66314 - 66322. Nothing in this section shall be interpreted to prohibit an ADU of up to 800 square feet, at the heights stated in Section 19.112.030(A) and .030(B), with a four‐foot side and rear setbacks.
  2. The Development Standards for units governed by this section are provided in Section 19.112.040. These regulations do not limit the height of existing structures converted into ADU/JADUs unless the envelope of the building is proposed to be modified beyond any existing legal, non‐conforming condition.


19.112.050 Review Process.

  1. Applications for accessory dwelling units conforming to the requirements of this chapter shall be reviewed ministerially without discretionary review and must be approved or denied within the time frame specified in Government Code Section 66317.
  2. Nonconforming zoning conditions, building code violations or unpermitted structures:
    1. The correction of nonconforming zoning conditions (as defined in Government Code Section 66313) shall not be required as a condition of approval of a permit for the creation of an ADU or a JADU.
    2. A permit for an ADU or a JADU will not be denied due to the correction of nonconforming zoning conditions, building code violations, or other unpermitted structures that do not present a threat to public health and safety and that are not affected by the construction of the ADU or JADU.
  3. Unpermitted ADU or JADU: Any ADU created within the City shall comply with all applicable provisions of the Municipal Code and state law, and must obtain a building permit confirming compliance with all requirements, except that:
    1. A permit to legalize an unpermitted ADU or JADU that was constructed before January 1, 2020 may not be denied, if denial is based on either of the following grounds:
      1. The ADU or JADU violates applicable building standards, or
      2. The ADU or JADU does not comply with state ADU or JADU law (Government Code Section 66313-66339) or this chapter.
    2. Notwithstanding the above, a permit to legalize an unpermitted ADU or JADU that was constructed before January 1, 2020 may be denied, if the City makes a finding that correcting violations of applicable building standards, state ADU/JADU law, and/or this municipal code, is necessary to comply with the standards specified in California Health and Safety Code section 17920.3.
    3. Notwithstanding subsection (C)(1) or (C)(2) above, a building that is deemed to be substandard in accordance with California Health and Safety Code Section 17920.3 shall not be permitted.

(Ord. 20-2199, § 5 (part), 2020; Ord. 16-2159, § 8 (part), 2016; Ord. 25-2274, Att. A (§ 1), 2025)


19.112.060 Accessory Dwelling Units Prohibited on Certain Lots.

Notwithstanding Government Code Section 66313 - 66339 or any provision of this Chapter, no accessory dwelling unit or a junior accessory dwelling unit shall be permitted on any lot in single-family residence district (R-1 or RHS) if an urban lot split has been approved pursuant to Section 18.12.70 and one or more residential unit(s) have been approved for construction pursuant to Section 19.28.150 or 19.40.090 (Government Code Section 65852.21).

(Ord. 22-2246, § III (part), 2022; Ord. 22-2238, § 3.14, 2022; Ord. 21-2235, § 3.14, 2021; Ord. 25-2274, Att. A (§ 1), 2025)


19.112.070 Enforcement.

  1. Violations of this Chapter shall be enforced as authorized by this Municipal Code and applicable provisions of state law.
  2. Enforcement of Building Code standards: In enforcing building standards pursuant to Article 1 (commencing with Section 17960) of Chapter 5 of Part 1.5 of Division 13 of the Health and Safety Code for an ADU described below, a local agency, upon request of an owner of an ADU for a delay in enforcement, shall delay enforcement of a building standard, subject to compliance with Section 17980.12 of the Health and Safety Code:
    1. The ADU was built before January 1, 2020.
    2. The ADU was built on or after January 1, 2020, and at the time the ADU was built, the City had a noncompliant ADU ordinance, but the ordinance is compliant at the time the request is made.

(Ord. 25-2274, Att. A (§ 1), 2025)


Table 19.112.030A: Site Development Regulations for Streamlined Accessory Dwelling Units and Junior Accessory Dwelling Units Associated with Single-Family Residential Uses

Conversion of space within principal dwelling unit or accessory structures

New Construction Attached or Detached Accessory Dwelling Unit ≤ 800 s.f.

1. Size of living space, exclusive of decks

a. Minimum size

150 s.f.

b. Maximum size

No size limitation as long as the unit:

  1. Is wholly within the space of a proposed or existing single-family dwelling or the existing space of an accessory structure, and
  2. Does not require either:
    • An addition of more than 150 square feet to an existing accessory structure to accommodate ingress and egress only, or
    • Any addition to an existing single-family dwelling unit.

800 s.f.

2. Number of Units

Maximum three ADUs per single‐family residential lot, in any combination of the following:

  • Attached ADU,
  • Conversion of existing space ADU (whether in principal dwelling unit or existing accessory structure),
  • Detached ADU, or
  • Junior ADU

3. Setbacks

Per the underlying zoning district except that if the existing structures do not meet these standards, the side and rear setbacks shall be sufficient for fire safety and life safety.

  1. At least four feet from the rear and side lot lines.
  2. An applicant alternately may elect to follow the setback standards for accessory structures in Chapter 19.100.

4. Height

The conversion shall not change the height of the existing structure.

  1. 18 feet for detached ADU
  2. If accessory dwelling unit is attached to principal dwelling, 25 feet or the height limitations applicable to the principal dwelling, whichever is lower.
  3. An applicant alternatively may elect to follow the height standards for accessory structures in Chapter 19.100.

5. Second-story accessory dwelling unit

Allowed if the unit is a conversion of existing second story portion of the principal dwelling unit.

Allowed

6. Parking for accessory dwelling unit

None

None

7. Direct outside access

Independent outdoor access must be provided without going through the principal dwelling unit.

8. Separation from principal dwelling unit

The conversion must result in an independent unit. With the exception of a JADU that has a shared bathroom with the principal dwelling unit, no interior doors or other connections between the units are permitted.

Detached from principal dwelling unit

1. An additional two feet in height ( from 18 to 20 feet) for ADUs within one half mile of a major transit stop or a high quality transit corridor is permitted to accommodate a roof pitch on the accessory dwelling unit that is aligned with the roof pitch of the primary dwelling unit.


Table 19.112.030B: Site Development Regulations for Streamlined Accessory Dwelling Units Associated with Existing Multi-Family Residential Uses

Conversion of interior space and JADUs within multifamily dwelling structures

Detached, and Attached New Construction

1.

Location

  1. Conversion of space within existing dwelling structures that is not used as livable space (e.g. existing units) including, but not limited to, storage rooms, boiler rooms, passageways, attics, basements, or garages, as long as the unit meets building standards for dwellings.
  2. JADUs permitted only in duplexes

Must be detached from the multi‐family dwelling structure(s) other than for duplex zoned properties, except attached ADUs are allowed for duplex zoned properties.

2.

Maximum Number of Units

a. Multifamily developments other than duplex zoned properties

i. The greater of:

  • 25 percent of the existing number of primary dwelling units, or
  • One accessory dwelling unit

ii. On a lot with an existing multi-family dwelling, the lesser of:

  • Eight detached accessory dwelling units and
  • the number of existing multi-family units on the lot.

iii. On a lot with a proposed multifamily dwelling, not more than two detached ADUs.

b. Duplex zoned properties

Up to a maximum of two accessory dwelling units in any combination of the following:

  • Attached ADU,
  • Conversion of existing space ADU (whether in principal dwelling unit or existing accessory structure),
  • Detached ADU, or
  • Junior ADU
3.

Minimum Size

150 s.f.

4.

Maximum Size

  • No size limitation
  • For duplex zoned properties, attached ADUs are limited to 800 s.f.
Conversion of interior space and JADUs within multifamily dwelling structuresDetached, and Attached New Construction
5.

Setbacks

The accessory dwelling unit shall not increase the size of the existing structure.

a. Located at least four feet from the side and rear lot lines.

b. An applicant alternately may elect to follow the setback and height standards for accessory structures in Chapter 19.100.

6.

Height

The accessory dwelling unit shall not increase the size of the existing structure.

a. 18 feet1

b. An applicant alternatively may elect to follow the setback and height standards for accessory structures in Chapter 19.100.

7.

Separation from principal dwelling units

The conversion must result in an independent unit. No interior doors or other connections between the units are permitted.

Detached from principal dwelling units.

1. An additional two feet in height (from 18 to 20 feet) for ADUs within one half mile of a major transit stop or a high-quality transit corridor is permitted to accommodate a roof pitch on the accessory dwelling unit that is aligned with the roof pitch of the primary dwelling unit.

(Ord. 20-2199, § 5 (part), 2020; Ord. 17-2170, § 4, 2018; Ord. 17-2165, § 12, 2017; Ord. 16-2159, § 8 (part), 2016; Ord. 2085, § 2 (part), 2011; Ord. 23-2254, Att. A (part), 2023; Ord. 25-2274, Att. A (§ 1), 2025)


Table 19.112.040: Site Development Regulations for Non-Streamlined Accessory Dwelling Units

Created by New Construction and/or Additions to the Principal Dwelling Unit

Attached > 800 s.f.

Detached > 800 s.f.

A.

Number of Units

1. A maximum of three ADUs per single‐family lot in any combination of the following, subject to the underlying zoning standards for lot coverage, floor area, open space, and setback:

  • No more than one attached ADU
  • No more than one conversion of existing space ADU (whether in principal dwelling unit or existing accessory structure),
  • No more than one detached ADU, or o No more than one Junior ADU

2. Nothing in this Section shall permit the development of more than three ADUs or Junior ADUs on any single‐family lot. Non‐streamlined ADU provisions cannot be combined with streamlined provisions to add more than a total of three ADUs.

B.

Size of living space, exclusive of decks

1. Minimum size

150 s.f.

2. Maximum size

  1. Studios/one-bedroom unit – 850 s.f.; two or more-bedroom unit – 1,000 s.f.; and
  2. Attached accessory dwelling units shall not exceed 50% of the existing primary dwelling
  3. Lot coverage, floor area, and open space standards per underlying zoning apply to ADUs grater than 800 s.f. See Table 19.112.030 A for requirements related to ADUs less than or equal to 800 s.f.
C.

Setbacks1

Per the underlying zoning district, except the required side and rear setbacks are modified to four feet.

The proposed structure must comply with the setback standards for accessory structures in Chapter 19.100, except the street side setbacks are modified to four feet.

Attached > 800 s.f.Detached > 800 s.f.
D.

Height

25 feet of the height limitations applicable to the principal dwelling, whichever is lower.

The proposed structure must comply with the height standards for accessory structures in Chapter 19.100, except that a maximum height of 18 feet is allowed within half a mile of a major transit stop or transit corridor.

E.

Second-story accessory dwelling units

Allowed within half a mile of a major transit stop or transit corridor.

F.

Parking

1. Parking for accessory dwelling unit

One additional off-street parking space shall be provided, if the principal dwelling unit has less than the minimum off-street parking spaces for the applicable residential zoning district in which it is located, as required in Chapter 19.124, and none if the accessory dwelling unit meets one of the following requirements:

  1. Located within one-half (1/2) mile of a public transit stop; or
  2. Located within one block of a car share vehicle pick‐up location; or
  3. Located in an architecturally and historically significant historic district; or
  4. The occupant of the unit is not allowed/offered a required on-street parking permit; or
  5. Is part of the proposed or existing primary residence or an accessory structure or
  6. When a permit application for an accessory dwelling unit is submitted with a permit application to create a new single-family dwelling on the same lot provided that the accessory dwelling unit or the parcel satisfies any other criteria listed above.

2. Demolition or conversion of existing covered, uncovered or enclosed parking spaces for an accessory dwelling unit

No replacement parking spaces are required.

Attached > 800 s.f.Detached > 800 s.f.
G.

Direct outside access

Independent outdoor access must be provided without going through the principal dwelling unit.

H.

Screening from public street

All access to accessory dwelling units shall be on a different wall plane than the access to the principal dwelling unit.

I.

Structure Design

  1. Shall match the exterior and roofing materials, window style, exterior lighting and exterior colors of the principal structure.
  2. Shall meet the design standards when located within any one of the following zoning districts:
    • Planned Development (P)
    • Eichler (R1-e)
    • Monta Vista Design Guidelines
    • Residential Hillside (RHS)
    • Single Family Residential District with Semi-Rural Characteristics (R1-a)
J.

Separation from principal dwelling unit

The ADU must be an independent unit. No interior doors or other connections between the ADU and the principal dwelling unit are permitted.

Detached from principal dwelling unit.

1. No setback is required for an accessory dwelling unit located within existing living area or an existing accessory structure, or an accessory dwelling unit that replaces an existing structure and is located in the same location and to the same dimensions as the structure being replaced.

(Ord. 20-2199, § 5 (part), 2020; Ord. 23-2254, Att. A (part), 2023; Ord. 25-2274, Att. A (§ 1), 2025)