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7 Chapter 27.19
ACCESSORY DWELLING UNITS AND JUNIOR ACCESSORY DWELLING UNITS—
RESIDENTIAL ZONES
Article I Accessory Dwelling Unit
27.19.010 Purpose.
The purpose of this Article is to set forth regulations to permit accessory dwelling units (ADUs) in accordance with state law.
27.19.020 ReservedDefinitions.
The definitions in this Section shall apply only to this Chapter. (a) “Accessory dwelling unit” (ADU) means an attached or detached residential dwelling unit which provides complete independent living facilities for one or more persons, is accessory to the primary residential dwelling unit(s), and includes permanent provisions for living, sleeping, eating, cooking facilities and sanitation on the same lot as a Single-Family Dwelling Structure or Multifamily Dwelling Structure is or will be situated.
(1) “Attached ADU” means an accessory dwelling unit that is attached to a primary residential dwelling unit, or portion thereof (including an attached garage or accessory structure).
(2) “Conversion ADU” means any accessory dwelling unit created by the conversion of any existing structure or portion thereof. The Conversion ADU may be created using existing structural components of the existing structure, or may be reconstructed to the same extent as the existing structure. (3) “Detached ADU” means an accessory dwelling unit that is separated from a primary residential dwelling unit.
(4) “New Construction ADU” means any accessory dwelling unit that does not meet the definition and requirements of a Conversion ADU. (5) “Nonexempt ADU" means an accessory dwelling unit that does not meet the definition of a State Exempt ADU.
(6) “State Exempt ADU” means an accessory dwelling unit that is created pursuant to Government Code Section 66323.
(7) “Multifamily ADU” means an accessory dwelling unit on a lot with an existing or proposed Multifamily Dwelling Structure.
(8) “Single-Family ADU” means an accessory dwelling unit on a lot with an existing or proposed Single-Family Dwelling Structure.
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7 (a) “ADU Living Area” means the interior conditioned space within an Accessory Dwelling Unit, such as areas used for living, sleeping, eating, cooking and sanitation, and may also include attic or basement areas connected to the ADU. ADU Living Area does not include non-habitable spaces such as garages, carports, unconditioned utility rooms, enclosed storage areas not internally accessible by the ADU, or other accessory structures attached to the ADU. (b) “Junior accessory dwelling unit” (JADU) means a unit that is no more than 500 square feet in size and contained entirely within an existing or proposed Single-Family Dwelling. (c) “Multifamily Dwelling Structure” means a structure with two or more attached primary residential dwelling units.
(d) “Single-Family Dwelling Structure" means a one-family dwelling primary residential unit that either stands alone on a lot or is detached from other primary residential dwelling unit(s) on the same lot.
27.19.030 Prohibition on Sale and Limitation on Rental. (a) An ADU shall not be sold separately from the primary residence, except as allowed by Government Code Section 66341.
(a)(b) A JADU shall not be sold separately from the primary residential dwelling unit. (b)(c) If an ADU or JADU is rented, the unit shall not be rented for a period of less than 30 consecutive calendar days.
27.19.040 Ministerial Permit Approval.
An ADU permit application for either an attached or a detached ADUan ADU and/or a JADU is required in order to demonstrate that athe unit is in compliance with the provisions of this ArticleChapter. If the ADU is in full compliance with the provisions of this ArticleChapter, a ministerial, non-discretionary permit will be issued. Notwithstanding anything to the contrary in this Code, the issuance of a ministerial ADU or JADU permit is not appealablemay not be appealed.
27.19.045 Discretionary Review as Alternative to Ministerial Approval. (a) As an alternative to ministerial review, an applicant may submit an application for discretionary review of an ADU proposal that is not in full compliance with the provisions of this Articleheight, setback, or daylight plane provisions of this Chapter, and/or for an ADU that proposes a second story deck or balcony exceeding the standards outlined in this Chapter. The discretionary review application shall not be used to increase the maximum allowable floor area of a lot.
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7 (a) The application for discretionary approval shall be granted if the Zoning Administrator finds each all of the following:
(1) The proposed ADU is consistent with all applicable objective design standards in the adopted R1 Single-Family Dwelling Design Guidelines.; (2) The proposed ADU would not result in a negative privacy impact on an abutting residential lot; and
(3)(2) The proposed ADU would not result in a negative impact to public health, safety, or welfare.
(4) The proposed ADU, when detached and exceeding the height limit, should provide at least one additional off-street parking space. (3) If the proposed ADU does not comply with height, setback, or daylight plane standards, there are exceptional circumstances applicable to the property that would make compliance with the standard(s) an undue hardship, and the deviations from applicable standards are minimized.
(4) If the proposed ADU includes a second story deck larger than 50 square feet, the deck or balcony is located and oriented to minimize direct views into neighboring windows or yard spaces, and screening is incorporated where necessary to minimize such views.
(5) The proposed ADU is consistent with all applicable provisions of the General Plan.
(b) The decision of the Zoning Administrator shall not preclude the ability of an applicant to receive a ministerial permit pursuant to Section 27.19.040 for an ADU that is in full compliance with the provisions of this ArticleChapter.
(c) The decision of the Zoning Administrator may be appealed to the City Manager or designee, which maybe a hearing officer. Planning Commission, and the decision of the Planning Commission may be appealed to the City Council, in accordance with SMMC
27.08.090.
(a) 27.19.050 Development Standards27.19.050 General Requirements Applicability. The following shall apply to ADUs and JADUs in all zoning districts that allow for residential uses:
(a) The provisions of this Chapter apply only to ADU Living Area. Accessory structures, such as garages, carports, non-habitable utility rooms, storage areas, or sheds, whether detached or attached to an ADU, shall be subject to the requirements of the underlying zoning district and other applicable provisions of the Zoning Code. 1 2
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7 (a) Development Impact Fees. Development impact fees for ADUs shall be established in an amount set forth by resolution of the City Council. No impact fees shall be charged for ADUs 750 square feet in size or smaller. Any impact fees charged for an ADU over 750 square feet shall be charged proportionately in relation to the square footage of the primary residential dwelling unit.
(b) Utility Service. For Conversion ADUs, a separate water connection, a sewer service connection, or power connection is not required. If an ADU is not converted from existing space, the City may require new or separate utility connections. (c) Utility Fees. For a Conversion ADU, payment of a connection fee or capacity charge is not required. For an ADU that is separate from an existing structure, the City will require payment of a connection fee or capacity charge that is proportionate to the ADU's burden. An ADU shall not be considered a new residential use for the purposes of calculating connection fees or capacity charges for utilities, including water and sewer service, except when the ADU is constructed with a new primary residential dwelling unit. (a) Address Assignment. An application for a building permit for an ADU must include application for a separate address assignment.
27.19.060 Single-Family ADU Development Standards
An ADU, as defined in Section 27.04.165, shall comply with the following development standards:
(a) Applicability. This section applies to ADUs located on a lot with an existing or proposed Single-Family Dwelling Structure. Number of Units. A lot with an existing or proposed Single-Family Dwelling Structure may include any combination of the following three types of ADUs, provided that each meets the applicable development standards. (1) One Attached or Conversion ADU.
(2) One Detached New Construction ADU.
(3) One JADU, provided it is located within the walls of an existing or proposed Single-Family Dwelling Structure.
(a) Permitted Zoning Districts. ADUs shall only be constructed on a lot zoned to allow residential uses.
(b) Number of Units. No more than the number of ADUs allowed by state law may be constructed on any lot.
(c) State Exempted "By Right" ADUs. An attached or detached ADU of at least 800 square-feet in size and of at least 16 feet in building height with four-foot side and rear setbacks may be constructed on a lot regardless of any size limitation based on the size of the proposed 1 2
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7 or existing primary dwelling, lot coverage, floor area ratio, daylight plane, open space, or minimum lot size that would otherwise preclude or limit its construction. The floor area of any new ADU in excess of 800 square feet shall be applied to the maximum floor area allowance of the subject lot as prescribed by the underlying zoning district. (d) Maximum Unit Size and Floor Area Ratio (FAR). Floor areaFAR and unit size maximums for both Aattached and Ddetached ADUs development in excess of 800 square feet are governed by the floor area maximum FAR established by the underlying zoning district and remaining floor area allowance available on the lot. In instances when the existing floor area allowance of a lot has been fully utilized, only the state exempted "by right" ADU of up to 800 square feet is permitted. Up to 800 square feet of ADU floor Living Area, including New Construction State Exempt ADUs, is exempt from the maximum FAR for each lot with a Single- Family Dwelling Structure. This exemption does not apply to JADU floor living area. In addition, the following shall apply:
(1) An ADU shall not be larger, in terms of floor living area, than the primary residential dwelling unit. However, when the primary residential dwelling unit is less than or equal to 800 square feet in size, a State Exempt ADU of up to 800 square feet is allowed.
(e)
(1)(2) Accessory Dwelling Unit Conversions. An ADU Ac Conversion ADU within the walls of an existing primary residence dwelling unit or accessory structure is not subject to size requirements. ADU conversions may be expanded up to 150 square feet beyond the existing footprint provided the expansion is used to accommodate ingress and egress to the ADU.
(2) Detached Accessory Dwelling Unit and Junior Accessory Dwelling Unit.
Subject to the floor area requirements, one new detached ADU may be constructed on a lot with a junior accessory dwelling unit (JADU).
(f)(e) Height. The specific height maximums are applicable to all zoning districts which permit ADUs.
(1) Attached Accessory Dwelling Units. Maximum building height for an attached ADU is 24 feet to top plateline and 32 feet to roof peak as measured from existing grade. (2) Detached Accessory Dwelling Units. Maximum building height for a detached ADU is 16 18 feet to top plateline and 24 feet to roof peak as measured from existing grade.
(3) Alternative Discretionary Review for Detached Accessory Dwelling Units. For a detached ADU proposed to exceed the height limit, an application for discretionary review, pursuant to Section 27.19.045, shall be submitted. 1 2
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7 (g) Setbacks. An ADU shall have setbacks as follows:
(1) No setback shall be required for an existing legally permitted garage or accessory structure that is converted to an ADU which is constructed in the same location and to the same dimensions, footprint, and height as the existing structure; or for a Detached ADU that is proposed in the rear one-third of a lot that otherwise meets all requirements of accessory buildings and structures in required yards of R1 districts pursuant to Chapter 27.70.
(2) A minimum setback of four feet shall be required from the side and rear lot lines for all new ADU construction not meeting the criteria set forth in subsection (1) above, including ADUs constructed above an existing legally permitted garage. (3) A minimum setback from the front lot line, as required in the lot's underlying zone district, shall be required for all Nnew Construction ADUs construction not meeting the criteria set forth in subsection (1) above, including ADUs constructed above an existing legally permitted garage. No front setback is required for a State Exempt ADU. (h) Unit Access. AnThe ADU , whether attached or detached, shallmust include provide a separate exterior entrance from the primary residential dwelling unit. An interior access may be provided between the two units, but is not required., and permanent provisions for living, sleeping, eating, cooking, and sanitation.
(i) Location of Accessory Dwelling Unit. The ADU may be within, attached to, or detached from the primary dwelling unit. ADUs shall be accessory to the primary residence and are permitted in the same locations on the parcel as the primary residence as specified in the underlying zoning district.
(j)(i) Number and Type of Required Parking SpacesADU and JADU Parking Standards. (1) General Requirements. There shall be a minimum of one standard size off- street parking space for each ADU. All required parking spaces shall be a minimum of 10 feet wide by 18 feet long without any obstructions. Parking associated with ADU or JADU development, whether required or voluntary, must be located entirely on the same lot, and may be provided in a garage, carport, uncovered, or in tandem orientation.
Additionally, maximum driveway width for single-car garages may be up to 20 feet to accommodate additional off-street parking. The required parking for the primary residential dwelling unit must comply with current standards, as specified by the underlying zoning district.
(2) Location of Parking for Accessory Dwelling Units. Parking for the accessory dwelling unit may be located in the required front, side, and rear yard setback areas. (3) Replacement off-street parking is not required when a garage, carport, or covered parking structure is demolished in conjunction with the construction of an ADU or converted to an ADU.
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7 (4) Parking Exemptions. No additional off-street parking shall be required for an ADU in the following instances:
A) The ADU is located within one-half (1/2) mile walking distance of public transit; or
B) The ADU is located within an architecturally and historically significant historic district; or
C) The ADU is in part of the proposed or existing legally permitted primary residence or an existing legally permitted accessory structure; or D) In an area requiring on-street parking, permits are required but not offered to the occupant of the ADU; or
E) When the ADU is located within one block of a car share location. (1) General Requirements. No off-street parking shall be required for any ADU or JADU. The required parking for the primary residential dwelling unit(s) must comply with the underlying zoning district’s current standards, except when an existing garage, carport, or covered parking structure, or uncovered parking space is converted to an ADU or JADU or demolished in conjunction with construction of an ADU. When this occurs, no replacement off-street parking is required for the primary residential dwelling unit.
(1) Voluntary Parking. If no parking space is required, a maximum of one off- street parking space per ADU or JADU may be voluntarily provided Off street parking for an ADU or JADU may be provided voluntarily. Voluntarily provided parking associated with ADU or JADU development must be located entirely on the same lot, and may be provided in a garage, carport, uncovered, or in tandem orientation. Additionally, the following provisions may be applied to create voluntary parking for an ADU or JADU.
A) When a garage or carport is converted to an ADU or JADU, or demolished in conjunction with construction of an ADU, the existing driveway and curb cut are not required to be removed, and may be maintained as parking area.
B) A maximum of up to two voluntarily provided parking stalls may be provided for each ADU or JADU.
C) The maximum driveway width for single-car garages may be up to 20 feet to accommodate additional off-street parking.
D) Uncovered parking for an ADU or JADU may be located in the required front, side, and rear yard setback areas. If a covered parking structure is proposed to provide voluntary parking below a second- 1 2
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7 story ADU, the parking structure may be located within the footprint of the proposed ADU, provided that it is outside of the front yard setback of the underlying zoning district. When a parking structure is proposed within a required side or rear setback of the underlying zoning district, the plate height of the parking structure shall not exceed 9 feet in height.
(1)
(k) Architectural Standards. New Nonexempt ADUs and conversions of an existing legally permitted structure shall be designed to comply with the following standards, as applicable:
(1) Attached Accessory Dwelling Units. ADUs that are attached to the primary dwelling unit shall:
A) Be of the same architectural style as the primary dwelling unit; B) Be constructed of similar exterior materials, finishes, and family of colors as the primary dwelling unit;
C) Offset windows from neighbor's windows to maximize privacy; and D)(1) Be designed to meet the daylight plane requirements of the R-1 zoning district as applied to the nearest adjacent side and rear lot lines. (i) Application of the daylight plane requirement shall not preclude a State Exempted "By Right" ADU as defined in this Chapter. (2) Detached Accessory Dwelling Unit. An ADU that is detached from the primary dwelling unit shall:
A) In instances when an ADU is attached to an accessory structure, provide a uniform and integrated design with that accessory structure; B) Offset windows from neighbor's windows to maximize privacy; C)(2) Provide and maintain obscured glazing on second-story windows up to five feet from the finished floor when the windows are located within five feet of a lot line with an abutting residential lot;.
(3)(1) When an exterior staircase is proposed, it shall have a setback of at least five feet from the nearest lot line and the size of the second story landing shall be limited to the minimum area required to allow ingress and egress as specified by the California Building Code;.
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7 (1) Rooftop decks or terraces above any portion of an ADU are prohibited. (2) When a second-story deck or balcony is proposed within a two-story ADU, the following shall apply:
A) Second story decks or balconies shall not be larger than 50 square feet in size; and
A)B) No portion of a second story deck or balcony shall be located within the setbacks of the underlying zoning, regardless of the ADU setbacks; and
B)C) Decks shall only face the interior of the subject property.
A)
(i) For an ADU that seeks to have a larger second story deck, an application for discretionary review, pursuant to Section 27.19.045, shall be submitted.
C) Be designed to meet the daylight plane requirements of the R-1 zoning district as applied to the nearest adjacent side and rear lot lines.
(l) Development Impact Fees. Development impact fees for ADUs shall be established in an amount set forth by resolution of the City Council.
(m) Utility Service. If an ADU is constructed within existing space, a separate water connection, a sewer service connection, or power connection is not required for an ADU. If an ADU is not constructed within existing space, the City may require new or separate utility connections.
(n) Utility Fees. For an ADU located within an existing structure, payment of a connection fee or capacity charge is not required. For an ADU that is separate from an existing structure, the City will require payment of a connection fee or capacity charge that is proportionate to the ADU's burden.
(o) Address Assignment. An application for a building permit for an ADU must include application for a separate address assignment.
(p) Other Requirements. All other zoning requirements shall be complied with unless an authorized variance is approved.
(q) For ADUs proposed within an existing multi-family structure or on a lot with an existing multi-family dwelling, the provisions of Government Code Section 65852.2(e)(1) apply. 1 2
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7 27.19.060 Reserved.
Article II Junior Accessory Dwelling Unit
27.19.070 PurposeMultifamily ADU Development Standards. (a) The purpose of this Article is to set forth regulations to permit junior accessory dwelling units (JADUs). Applicability. This section applies to all ADUs located on lots with existing or proposed Multifamily Dwelling Structure(s). (b) Number of Units Allowed.
(1) On a lot with a proposed Multifamily Dwelling Structure, up two new Detached ADUs may be allowed.
(2) On a lot with an existing Multifamily Dwelling Structure, the following ADUs may be permitted in combination:
A) Up to eight New Construction Detached ADUs may be allowed, provided that the number of ADUs shall not exceed the number of existing primary residential dwelling units on the lot.
B) Conversion ADUs created by converting non-living space within an existing Multifamily Dwelling Structure. The number of non-living space Conversion ADUs may be at least one, and not more than 25 percent of the number of existing primary residential dwelling units.
C) Any additional ADUs as allowed pursuant to State Law. (c) Maximum Unit Size.
(1) An ADU shall not have a larger floor living area than the smallest primary residential dwelling unit on a lot. When the smallest primary residential dwelling unit is less than 800 square feet, then a State Exempt ADU of up to 800 square feet is allowed. (2) A Conversion ADU within the existing space of a Multifamily Dwelling Structure is not subject to size requirements.
(3) Floor Area Ratio (FAR). Floor area size maximums for both Attached and Detached ADUs are governed by the floor area maximum established by the underlying zoning district and remaining floor area allowance available on the lot. Up to 800 square feet of ADU Living Area is exempt from total FAR for the lot. The exemption for ADU floor Living Area up to 800 square feet shall be applied individually to each new Detached ADU proposed on a lot with an existing or proposed Multifamily Dwelling Structure.
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7 (1) In instances when the existing floor area allowance of a lot has been fully utilized, only New Construction State Exempt ADUs of up to 800 square feet are allowed.
(a) Height - Maximum building height for a new Detached Multifamily ADU is 18 feet to top plateline and 24 feet to roof peak as measured from existing grade. (b) Setbacks.
(1) For new Detached Multifamily ADUs, a minimum setback of four feet from side and rear property lines is required.
(2) A minimum setback from the front lot line, as required in the lot's underlying zone district, shall be required for all new Multifamily ADUs. No front setback is required for a New Construction Detached State Exempt ADU.
(c) Parking. The single-family development parking standards of this Chapter shall apply to Multifamily ADUs.
(d) Architectural standards. The single-family development architectural standards of this Chapter shall apply to Nonexempt ADUs on lots with an existing or proposed Multifamily Dwelling Structure.
(e) Separation between structures. New Detached Multifamily ADUs shall be separated from the primary structure by a minimum of four feet, open to the sky. Where multiple new Detached ADUs are proposed, the ADUs may be attached to each other, but must be detached from the primary structure.
27.19.080 Reserved.
27.19.090 Prohibition on Sale and Limitation on Rental. (a) A JADU shall not be sold separately from the primary residence. (b) If a JADU is rented, the unit shall not be rented for a period of less than 30 consecutive calendar days.
27.19.100 Ministerial Permit Required.
A JADU permit application is required in order to demonstrate that the unit is in compliance with the provisions of this Article. If the JADU is in full compliance with the provisions of this Article, a ministerial, non-discretionary permit shall be issued.
27.19.110080 JADU Development Standards.
(a) Applicability. The development standards in this section shall apply to all JADUs. 1 2
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7 A "junior accessory dwelling unit," as defined in Section 27.04.165, must comply with the following development standards:
(a) Permitted Zoning Districts. JADUs shall only be constructed on lots zoned to allow single-family residential use, or for which a Ssingle-fFamily residence Dwelling Structure exists or is proposed to be built. The residential lot shall not be part of a condominium, townhouse, or other multi-family developmentMulti-Family Dwelling Structure. (b) Limit to the Number of Junior Accessory Dwelling UnitsJADUs permitted. The number of JADUs is limited to one per residential lot with a Ssingle-Ffamily residenceResidential Dwelling Structure. Lots with mMulti-Ffamily housing Dwelling or more than one detached single-family dwelling are not eligible for JADUs. (c) Setback and Other Zoning Regulations. For purposes of setbacks and other zoning regulations, the JADU shall be considered to be a part of the principal use of subject site and shall be subject to the same requirements of the underlying zoning district. (d) Maximum Unit Size. The floor living area of a JADU shall not exceed 650 500 square feet, including attic and basement areas as defined in Section 27.04.200 for the applicable zoning district.
(e) Construct within Existing Structure. The JADU shall be constructed within the walls of the proposed or legally existing single-family dwelling unit, including an attached garage.
Detached accessory structures, including detached garages or carports, are not permitted to be converted into JADUs.
(f) Unit Access. A JADU must include:
(1) A separate exterior entry from the main entrance to the single-family dwelling, which shall be provided to serve the JADU only; and
(2) When a JADU shares sanitation facilities or utility controls (such as a thermostat for heating and cooling), Aan interior entry access between the JADU and the Ssingle-fFamily dwellingDwelling Structure is required. This interior entry access may be a door equipped with a double lock. A permitted JADU may include a second interior door for sound attenuation. For a JADU with its own sanitation facilities and utility controls, interior access is not required, but may be provided voluntarily. (g) Efficiency Food Preparation Area. A JADU shall include an efficiency kitchen that includes the following components:
(1) Cooking facility with appliances; and
(2) Food preparation counter and storage with cabinets that are of reasonable size in relation to the size of the JADU.
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7 (h)(a) Sanitation Facilities. A JADU may include its own separate sanitation facilities or may share sanitation facilities with the primary dwelling unit. (i)(b) Building and Fire Requirements.
(1) No fire wall separation or noise attenuation measures are required between the main dwelling and the JADU. No fire sprinklers are required for the JADU, unless the associated improvements meet the threshold for a "substantial remodel" as defined by Chapter 23, Building and Construction, of the San Mateo Municipal Code. The JADU shall have an adjoining door connected to the main living area for fire separation. A smoke alarm shall be required in the JADU and shall be connected to the smoke alarm in the main residence.
(2) The JADU shall be equipped with a carbon monoxide detector. (j)(c) Utility Service. A sSeparate water connection, a separate sewer service connection, and power connection as water, sewer, and power service is are not required for a JADU.
(k)(d) Parking. No additional off-street parking is required for a JADU. (a) Address Assignment. An application for a building permit for a JADU must include application for a separate address assignment.
(l)(e) Owner Occupancy. If the junior accessory dwelling unit has shared sanitation facilities with the existing structure, owner-occupancy shall be required. The owner may reside in either the remaining portion of the structure or the newly created JADU. Owner-occupancy shall not be required if the JADU has its own sanitation facilities, or if the owner is another governmental agency, land trust, or housing organization.
27.19.120090 Recordation ofJADU Deed Restriction.
(a) Prior to building permit issuance for a JADU, aA deed restriction shall be recorded to run with the land and submitted to the City prior to building permit issuance whichto indicates the following:
(1) The property owner must occupy either the single-family residence or the JADU.
(2) If the JADU is rented, the unit shall not be rented for a period of less than 30 consecutive calendar days.
(3)(1) Sale of the JADU separately from the single-family residence is prohibited. (4)(2) The approved size and attributes of the JADU.
(b) A copy of this deed restriction must be given to each prospective occupant.