Millbrae City Zoning Code
ARTICLE XXXII
Accessory Dwelling Units
§ 10.05.3200 Definitions.
A.
"Accessory dwelling unit" or "ADU"
means an attached or detached residential dwelling unit that provides complete independent living facilities for one or more persons and is located on a lot with a proposed or existing primary dwelling. It shall include permanent provisions for living, sleeping, eating, cooking, and sanitation on the same parcel that the single-family or multifamily dwelling is or will be situated. "Accessory dwelling unit" includes an efficiency unit, as defined in Section 17958.1 of the California Health and Safety Code, or a manufactured home, as defined in Section 18007 of the California Health and Safety Code. An accessory dwelling unit is not an accessory structure, as defined in MMC § 10.05.0200, nor is it subject to the requirements of Article XX of this chapter. Notwithstanding the forgoing sentence, an accessory structure, as defined in MMC § 10.05.0200 may be converted into an accessory dwelling unit or a portion of an accessory dwelling unit in compliance with the requirements of this article.
B.
"Junior accessory dwelling unit" or "JADU"
means a unit that is no more than five hundred square feet in size and contained entirely within a single-family dwelling or attached garage. A junior accessory dwelling unit shall contain at least an efficiency kitchen that includes a cooking facility with appliances and a food preparation counter and storage cabinets that are of reasonable size in relation to the junior accessory dwelling unit. A junior accessory dwelling unit may include separate sanitation facilities or may share sanitation facilities with the existing structure. A junior accessory dwelling unit is not an accessory structure, as defined in MMC § 10.05.0200, nor is it subject to the requirements of Article XX of this chapter.
C.
"Primary dwelling" or "primary dwelling unit"
means a building designed and used exclusively for residential occupancy and which, at a minimum, contains one kitchen, bathroom facilities, and sleeping quarters. For purposes of this article, the single-family or multifamily residence in which an accessory dwelling unit or junior accessory dwelling unit is located within, attached to, or detached from is considered the primary dwelling.
(Ord. 782 § 1)
§ 10.05.3210 Purpose and applicability.
A.
The purpose of this article is to provide for accessory dwelling units and junior accessory dwelling units in accordance with applicable state law.
B.
In cases of conflict between this article and any other provision of this title, the provisions of this article shall prevail. To the extent that any provision of this article is in conflict with state law, the applicable provision of state law shall control, but all other provisions of this article shall remain in full force and effect.
(Ord. 782 § 1)
§ 10.05.3220 Applications and processing.
A.
A permit application to create a junior accessory dwelling unit or an accessory dwelling unit shall be ministerially considered and approved, without discretionary review or a hearing, within sixty days of receipt of a complete application that meets the requirements of this article if there is an existing single-family or multifamily dwelling on the lot. Incomplete applications will be returned with an explanation of the additional information that is required.
B.
Notwithstanding subsection A of this section, if the permit application to create a junior accessory dwelling unit or an accessory dwelling unit is submitted with a permit application to create a new single-family dwelling on the lot, the application for the junior accessory dwelling unit or accessory dwelling unit shall not be acted upon until the application for the new single-family dwelling is approved. Thereafter, the permit application for the junior accessory dwelling unit or accessory dwelling unit shall be ministerially considered and approved, without discretionary review or a hearing, within sixty days of receipt of a complete application that meets the requirements of this article. Occupancy of the junior accessory dwelling unit or accessory dwelling unit shall not be allowed until the city approves occupancy of the single-family dwelling.
C.
All permit applications for junior accessory dwelling units or accessory dwelling units shall be accompanied by an application fee.
D.
All junior accessory dwelling units and accessory dwelling units are subject to applicable city building inspection fees and permit fees.
(Ord. 782 § 1)
§ 10.05.3230 Locations allowed.
A.
Accessory dwelling units are permitted uses in all areas zoned to allow single-family or multifamily dwelling residential use.
B.
Junior accessory dwelling units may be developed on any legally created lot zoned to allow single-family residential use and shall be located within the walls of the existing or proposed primary dwelling or a legally permitted garage.
C.
Accessory dwelling units may be located in any of the following places on a legally created lot that is zoned to allow single-family or multifamily dwelling residential use and contains a proposed or existing primary dwelling:
1.
Attached to an existing or proposed primary dwelling.
2.
Located within the walls of an existing or proposed primary dwelling.
3.
Located within, or attached to, an existing accessory structure, as defined in MMC § 10.05.0200.
4.
Detached from an existing or proposed primary dwelling.
5.
On a lot with an existing multifamily dwelling structure, an attached accessory dwelling unit is permitted within the portions of the existing multifamily dwelling structure(s) that are not used as livable space, including, without limitation, storage rooms, boiler rooms, passageways, attics, basements, or garages; provided, that the accessory dwelling unit complies with the California Building Standards Code as set forth in MMC Title 9 for dwellings. The number of attached accessory dwelling units permitted on a lot with an existing multifamily dwelling structure shall be at least one and up to twenty-five percent of the existing multifamily dwelling units on the lot.
6.
On a lot with an existing multifamily dwelling structure, up to two detached accessory dwelling units are permitted; provided, that the accessory dwelling structures' heights do not exceed sixteen feet and four-foot side and rear yard setbacks are maintained.
D.
An accessory dwelling unit may be allowed in conjunction with a junior accessory dwelling unit on a lot with an existing or proposed single-family residence when the requirements of this article are met.
E.
Accessory dwelling units or junior accessory dwelling units cannot be constructed on any easements located on the lot.
(Amended by Ord. 804 § 2; Ord. 782 § 1)
§ 10.05.3240 General requirements.
A.
Junior Accessory Dwelling Units.
1.
The number of junior accessory dwelling units on lots zoned for single-family residential use is limited to one per lot with a proposed or existing single-family residence.
2.
Owner Occupancy. Owner occupancy in the single-family residence in which the junior accessory dwelling unit will be permitted is required. The owner may reside in either the remaining portion of the structure or the newly created junior accessory dwelling unit. Owner occupancy shall not be required if the owner is another governmental agency, land trust, or housing organization.
3.
Junior accessory dwelling units shall not be sold separately from the primary dwelling.
4.
Junior accessory dwelling units may be rented independently of the primary dwelling.
5.
Junior accessory dwelling units may not be rented for fewer than thirty consecutive calendar days. Junior accessory dwelling units may not be used as short-term residential rentals pursuant to the Short-Term Residential Rental Ordinance in Chapter 7.30 MMC.
6.
Prior to issuance of a building permit for a junior accessory dwelling unit, the owner shall record a deed restriction, which shall run with the land, and be in a form prescribed by the city attorney, filed with the community development department, and contain the following:
a.
A prohibition on the sale of the junior accessory dwelling unit separate from the sale of the single-family residence, including a statement that the deed restriction may be enforced against future purchasers; and
b.
A restriction on the size and attributes of the junior accessory dwelling unit consistent with this article.
B.
Accessory Dwelling Units.
1.
The number of accessory dwelling units on lots zoned for single-family residential use is limited to one per lot.
2.
Accessory dwelling units shall not be sold separately from the primary residence, except where permitted by Section 65852.26 of the California Government Code, as may be amended.
3.
Accessory dwelling units may be rented independently of the primary dwelling.
4.
Accessory dwelling units may not be rented for fewer than thirty consecutive calendar days. Accessory dwelling units may not be used as short-term residential rentals pursuant to the Short-Term Residential Rental Ordinance in Chapter 7.30 MMC.
5.
For applications received prior to January 1, 2025, there is no requirement for a legal owner of the parcel to reside in either the primary dwelling or the accessory dwelling unit on the parcel. Beginning January 1, 2025, the legal owner of the parcel must reside in either the primary dwelling or the accessory dwelling unit on the parcel.
(Amended by Ord. 804 § 3; Ord. 782 § 1)
§ 10.05.3250 Development standards.
A.
Junior accessory dwelling units and accessory dwelling units shall comply with all applicable building code requirements for dwellings. In no event will an accessory dwelling unit or junior accessory dwelling unit be required to provide fire sprinklers if fire sprinklers are not required for the primary dwelling.
B.
All development standards contained in the underlying zoning district shall apply to junior accessory dwelling units and accessory dwelling units unless they are inconsistent with the provisions of this article, in which case the development standards of this article shall apply.
C.
The development standards contained in this article will be waived to the extent necessary to ministerially approve accessory dwelling units and junior accessory dwelling units in accordance with Government Code Section 65852.2(e)(1).
D.
Junior Accessory Dwelling Units.
1.
General Requirements. No junior accessory dwelling unit shall be smaller than the size required to allow an efficiency unit pursuant to Health and Safety Code Section 17958.1, as may be amended. A junior accessory dwelling unit may, but is not required to, include separate sanitation facilities. If separate sanitation facilities are not provided, the junior accessory dwelling unit shall share sanitation facilities with the primary residence.
2.
Height. Maximum height of the junior accessory dwelling unit shall be the same as the height requirements for a single-family structure.
3.
Floor Area and Kitchen. A junior accessory dwelling unit shall not exceed five hundred square feet in size, shall be contained entirely within the walls of a single-family residence, and shall contain at least an efficiency kitchen that includes a cooking facility with appliances and a food preparation counter and storage cabinets that are of reasonable size in relation to the junior accessory dwelling unit.
4.
Entrances. A junior accessory dwelling unit shall have a separate entrance from the primary dwelling unit.
5.
Balconies and Decks. No balcony, deck or open stair landing of a junior accessory dwelling unit that faces the rear or side property line nearest the junior accessory dwelling unit shall be permitted, unless needed to allow ingress and egress. Exceptions to this development standard may be granted by the planning commission in the manner provided in Article XXV of this chapter.
6.
Parking. Junior accessory dwelling units shall not be required to provide for any additional parking or make up for any parking displaced by their construction, including conversion of all or part of an existing garage.
E.
Accessory Dwelling Units.
1.
General Requirements. No accessory dwelling unit shall be smaller than the size required to allow an efficiency unit pursuant to Health and Safety Code Section 17958.1, as may be amended.
2.
Height and Stories.
a.
The maximum height of an accessory dwelling unit attached to the primary dwelling unit shall be twenty-five feet, measured from finished grade to roof ridge, from all corners of the finished accessory dwelling unit. The plate height of an attached two-story accessory dwelling unit, or second story accessory dwelling unit, to an existing or proposed two-story home, shall be no higher than the plate height of the primary dwelling unit to which it is attached. An attached accessory dwelling unit shall not contain more than two stories.
b.
The maximum height of a detached accessory dwelling unit shall be eighteen feet for accessory dwelling units that are either: (i) within one-half mile walking distance of a major transit stop or a high-quality transit corridor, as defined in Public Resources Code Section 21155; or (ii) on a lot with an existing or proposed multifamily dwelling that is multistory. An additional two feet in maximum height may be permitted to accommodate a roof pitch on the accessory dwelling unit that is aligned with the roof pitch of the primary dwelling unit. The maximum height for all other accessory dwelling units on the parcel shall be sixteen feet, measured from finished grade to roof ridge, from all corners of the finished accessory dwelling unit. The maximum plate height of detached accessory dwelling units shall be nine feet. A maximum of thirty-six inches measured from finished grade may be added to the plate height to accommodate a crawlspace. A detached accessory dwelling unit shall not contain more than one story.
3.
Floor Area. The total floor area of an attached or detached accessory dwelling unit, exclusive of decks or balconies, shall be a minimum of one hundred fifty square feet and shall not exceed eight hundred fifty square feet for an accessory dwelling unit that contains a studio or one bedroom or one thousand square feet for an accessory dwelling unit that contains more than one bedroom. The total floor area of an accessory dwelling unit attached to an existing primary dwelling shall not exceed fifty percent of the floor area of the existing primary dwelling (garage and shed areas excluded).
4.
Entrance. An accessory dwelling unit shall have a separate entrance from the primary dwelling unit.
5.
Setbacks. Except as specified below, an accessory dwelling unit shall be required to comply with the setback requirements of the zone in which the unit is to be located.
a.
Conversions. No setback is required for an existing legally permitted living area or accessory structure converted to an accessory dwelling unit, or for a new accessory dwelling unit constructed in the same location and built to the same dimensions as an existing legally permitted structure.
b.
For all new attached or detached accessory dwelling units, a minimum setback of four feet is required from the rear and side property lines. The minimum separation from an accessory dwelling unit to the existing or proposed single-family, duplex or triplex, multifamily building, or other accessory structure shall be five feet. Detached accessory dwelling units shall be located within the rear half of the lot, unless such a requirement would preclude the construction of a detached accessory dwelling unit that is up to eight hundred square feet and up to sixteen feet in height with four-foot side and rear yard setbacks.
6.
Architectural Requirements. An accessory dwelling unit, whether attached or detached, and a junior accessory dwelling unit, must match the roof material, roof color, roof slope, exterior material, exterior texture, exterior color, window type, window material, window design, window color, and window recess of the existing or proposed primary dwelling unit. In addition, the design and type of materials shall be identical to the design and type materials of the primary dwelling. Accessory dwelling units shall be consistent with applicable residential design standards. The appearance of the single-family residence shall remain that of a single-family residence, as determined by the community development director or his/her designee.
7.
Balconies and Decks. No balcony, deck or open stair landing of an accessory dwelling unit that faces the rear or side property line nearest the accessory dwelling unit shall be permitted, unless needed to allow ingress and egress. Exceptions to this development standard may be granted by the planning commission in the manner provided in Article XXV of this chapter.
8.
Parking. Parking for an accessory dwelling unit shall be as follows:
a.
Except as provided in subsection (E)(8)(b) of this section, there must be one parking space per accessory dwelling unit. Accessory dwelling unit parking requirements are in addition to the parking required for the primary dwelling as provided in MMC § 10.05.2100. Parking spaces for an accessory dwelling unit may be provided as tandem parking on a driveway or in setback areas, unless the community development director makes specific findings that tandem parking or parking in setback areas is not feasible because of specific site or regional topographical conditions and/or fire and life safety conditions.
b.
No parking may be required for an accessory dwelling unit if any of the following apply:
i.
The accessory dwelling unit is part of the proposed or existing primary dwelling or an accessory structure.
ii.
The accessory dwelling unit is located within one-half mile walking distance of public transit. For purposes of this section, "public transit" means a location, including, but not limited to, a bus stop or train station, where the public may access buses, trains, subways, and other forms of transportation that charge set fares, run on fixed routes, and are available to the public.
iii.
The accessory dwelling unit is located within an architecturally and historically significant district.
iv.
When on-street parking permits are required but not offered to the occupants of the accessory dwelling unit.
v.
When a designated parking, pick-up or drop-off area for one or more car-share vehicles is located within one block of the accessory dwelling unit.
c.
When a garage, carport, or covered parking structure is demolished to construct an accessory dwelling unit within the demolished structure's footprint, or converted to an accessory dwelling unit, such off-street parking spaces need not be replaced, including the parking required pursuant to subsection (E)(8)(a) of this section.
(Amended by Ord. 804 § 4; Ord. 782 § 1)
§ 10.05.3260 Utilities and impact fees.
A.
No accessory dwelling unit shall be permitted if the public works department determines that there is a lack of adequate water or sewer service to the property.
B.
Except as provided in subsection C of this section, an accessory dwelling unit may be required to have a new or separate utility connection, including a separate sewer lateral, between the accessory dwelling unit and the utility. A connection fee or capacity charge may be charged that is proportionate to the burden of the proposed accessory dwelling unit, based upon either its square feet or the number of its drainage fixture unit (DFU) values, as defined in the Uniform Plumbing Code adopted and published by the International Association of Plumbing and Mechanical Officials, upon the water or sewer system. This connection fee or capacity charge shall not exceed the reasonable cost of providing this service.
C.
The following are exempt from any requirement to install a new or separate utility connection and to pay any associated connection fees or capacity charges:
1.
A junior accessory dwelling unit that complies with this article.
2.
An accessory dwelling unit located within the proposed space of a single-family primary dwelling or existing space of a single-family primary dwelling or accessory structure, unless the accessory dwelling unit was constructed with a new single-family home.
D.
All utility extensions shall be placed underground.
E.
Impact Fees.
1.
No impact fees may be imposed on a junior accessory dwelling unit or accessory dwelling unit that is less than seven hundred fifty square feet in size. For purposes of this section, "impact fees" include the fees specified in Sections 66000 and 66477 of the Government Code, but do not include utility connection fees or capacity charges.
2.
For accessory dwelling units that have a floor area of seven hundred fifty square feet or more, impact fees shall be charged proportionately in relation to the square footage of the primary dwelling unit.
(Ord. 782 § 1)
§ 10.05.3270 Delay of enforcement of building standards.
A.
For purposes of this section, "building standards" refers to those provisions of the State Building Standards Code enforced by the city pursuant to Article 1 (commencing with Section 17960) of Chapter 5 of Part 1.5 of Division 13 of the California Health and Safety Code.
B.
Until January 1, 2030, any notice to correct a violation of any provision of any building standard applicable to an accessory dwelling unit that is issued to the owner of an accessory dwelling unit built prior to the adoption of the ordinance codified in this article shall include a statement that the owner has a right to request a delay in enforcement of the building standard for an accessory dwelling unit pursuant to this section.
C.
The owner of an accessory dwelling unit that was built prior to the adoption of the ordinance codified in this article who receives a notice to correct a violation of a building standard may submit an application, in a form prescribed by the city, to the building official requesting enforcement of the violation be delayed for up to five years. The application will be granted if the building official determines that correcting the violation is not necessary to protect health and safety. In making this determination, the building official shall consult other regulations of the State Fire Marshal pursuant to Section 13146 of the California Health and Safety Code.
D.
No applications for delayed enforcement of building standards violations pursuant to this section shall be approved on or after January 1, 2030. However, any delay that was approved by the city before January 1, 2030, shall be valid for the full term of the delay that was approved at the time of the approval of the application pursuant to this section.
E.
This section shall remain in effect until January 1, 2035, and as of that date is repealed.
(Ord. 782 § 1)
