Chapter 17.52

ACCESSORY DWELLING UNITS

Sections:

• 17.52.010 Purpose.

• 17.52.020 Zones Allowed. 17.52.030 Definitions. 17.52.040 Development Standards and General Requirements. 17.52.050 Application Review.

The purpose of this chapter is to regulate accessory dwelling units in residential zoning districts and on residential property consistent with state law (California Government Code Section 65852 et seq.). Implementation is intended to provide for additional housing opportunities by increasing the number of units available within existing neighborhoods while maintaining the character of the area. The City Council of the Town of Atherton adopts this chapter to comply with Senate Bills (SB) SB 13, SB 477, SB 543, and SB 1211, and Assembly Bills (AB) AB 68, AB 462, AB 881, AB 1332, AB 2221, AB 2097, and AB 2553, under protest, as it is the Council’s position that in enacting these laws, the legislature has improperly usurped local land use authority. (Ord. 675 § 4, 2025; Ord. 665 § 3, 2024)

The Atherton Municipal Code is current through Ordinance 677, passed February 18, 2026.

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Junior accessory dwelling units shall be allowed in all areas zoned to allow single-family residential uses, and accessory dwelling units shall be allowed in all areas zoned to allow single-family residential and multifamily residential uses in compliance with the development standards set forth in section 17.52.040 (Development Standards and General Requirements) of this Chapter. (Ord. 675 § 4, 2025; Ord. 665 § 3, 2024)

A. “Accessory dwelling unit” or “ADU” means a building or portion of a building designed for use and occupancy by people living independently of the occupants of the main residence building. The ADU shall be on the same lot as the main residence. An ADU can be an attached or a 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 singlefamily or multifamily development. It shall include permanent provisions for living, sleeping, eating, cooking, and sanitation. An accessory dwelling unit also includes the following:

1. An efficiency unit.

2. A manufactured home, as defined in California Health and Safety Code Section 18007

• B. “Attached accessory dwelling unit” means a newly constructed unit that structurally abuts and is connected to the primary single-family home by at least one wall.

• C. “Detached accessory dwelling unit” means an accessory dwelling unit that is not structurally attached to the main residence.

D. “Efficiency unit” has the same meaning as defined in Section 17958.1 of the Health and Safety Code, which includes all the following:

1. Size of at least one hundred fifty square feet.

2. For units that are not accessible or adaptable, a partial kitchen with a sink, a permanently installed two or more burner cooktop and oven, hood vent, and refrigerator, each having a clear working space of not less than thirty inches in front of the counter.

   • a. Food preparation counter or counters.

   • b. Storage cabinets.

   • c. A separate closet.

3. Compliance with light and ventilation requirements of the Atherton Building Code.

4. A separate bathroom containing a water closet (toilet), lavatory (bathroom sink) and bathtub and/or shower.

The Atherton Municipal Code is current through Ordinance 677, passed February 18, 2026.

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E. “High-quality transit corridor” pursuant to California Public Resources Code Section 21155 means a corridor with fixed route bus service with service intervals no longer than fifteen minutes during peak commute hours. A project shall be considered to be within one-half mile of a major transit stop or high-quality transit corridor if all parcels within the project have no more than twenty-five percent of their area farther than one-half mile from the stop or corridor and if not more than ten percent of the residential units or one hundred units, whichever is less, in the project are farther than one-half mile from the stop or corridor.

ered to be within one-half mile of a major transit stop or high-quality transit corridor if all parcels within the project have no more than twenty-five percent of their area farther than one-half mile from the stop or corridor and if not more than ten percent of the residential units or one hundred units, whichever is less, in the project are farther than one-half mile from the stop or corridor.

F. “Junior Accessory dwelling unit” or “JADU” means a unit that is no more than five hundred square feet of interior livable space in size and contained entirely within a single-family residence. A junior accessory dwelling unit shall include an efficiency kitchen, which shall include all of the following: a cooking facility with appliances and a food preparation counter and storage cabinets that are of reasonable size in relation to the size of the junior accessory dwelling unit. A junior accessory dwelling unit may include separate sanitation facilities or may share sanitation facilities with the existing structure.

G. “Livable space” means a space in a dwelling intended for human habitation, including living, sleeping, eating, cooking, or sanitation.

H. “Living area,” for the purpose of this chapter, means the interior habitable area of a dwelling unit, including basements and attics, but does not include a garage or any accessory structure.

I. “Major Transit Stop,” pursuant to California Public Resources Code Sections 21064.3 and 21155, means a site containing an existing rail or bus rapid transit station, a ferry terminal served by either a bus or rail transit service, the intersection of two or more major bus routes with a frequency of service interval of twenty minutes or less during the morning and afternoon peak commute periods, or major transit stops that are included in the applicable regional transportation plan. A project shall be considered to be within one-half mile of a major transit stop if all parcels within the project have no more than twenty-five percent of their area farther than one-half mile from the stop or corridor and if not more than ten percent of the residential units or one hundred units, whichever is less, in the project are farther than one-half mile from the stop or corridor. For the purposes of this chapter, “public transit” is included in this definition.

J. “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. (Ord. 675 § 4, 2025; Ord. 665 § 3, 2024)

Unless otherwise stated in section 17.52.050, ADUs and JADUs are permitted, provided the following standards and requirements are incorporated and met:

A. Accessory Dwelling Use. All ADUs and JADUs shall be located on the same lot with an existing or proposed dwelling and considered an accessory residential use to the primary residence. ADUs and JADUs do not count towards the allowable density for the lot upon which it is located.

The Atherton Municipal Code is current through Ordinance 677, passed February 18, 2026.

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• B. Maximum Number of ADUs and JADUs Per Lot.

  1. One ADU and one JADU per lot with a proposed or existing single-family dwelling if all of the following apply:

     • a. The ADU or JADU is within the proposed space of a single-family dwelling, existing space of a singlefamily dwelling or in an accessory structure. The ADU may include an expansion of not more than one hundred fifty square feet beyond the same physical dimensions as an existing accessory structure. An expansion beyond the physical dimensions of an existing accessory structure shall be limited to accommodating ingress and egress.

     • b. The space has exterior access separate from the proposed or existing single-family dwelling.

     • c. The side and rear setbacks are sufficient for fire and safety.

     • d. The JADU complies with the requirements of California Government Code Section 66333.

  2. One detached new construction ADU that:

a. does not exceed eight hundred square feet, complies with the height restrictions in this section, and provides a minimum of four-foot side and rear yard setbacks for a lot with a proposed or existing singlefamily dwelling. The accessory dwelling unit may be combined with a JADU; Or

• b. does not exceed one thousand two hundred square feet, complies with the height and setback restrictions in this section, and is located on a lot with a proposed or existing single-family dwelling. The accessory dwelling unit may be combined with a JADU.

3. On lots that allow single-family dwellings and are a minimum of two acres, the property owner may have a detached “bonus” ADU provided the following conditions are met:

a. The bonus ADU is deed restricted as a housing unit available to a low-income household for a period of fifteen years or a very low-income household for a period of ten years. Income levels shall be consistent with the income limits established by the U.S. Department of Housing and Urban Development (HUD) and based on the Area Median Income (AMI) for San Mateo County.

• b. The bonus ADU must be rented for a period of nine months or longer.

• c. The bonus detached ADU must comply with the setbacks for accessory buildings and structures in section 17.40.040(A).

4. Lots that allow multifamily dwellings.

a. Multiple accessory dwelling units are allowed within the portions of existing multifamily dwelling structures that are not used as livable space, including, but not limited to, storage rooms, boiler rooms, passageways, attics, basements, or garages, if each unit complies with state building standards for dwellings.

The Atherton Municipal Code is current through Ordinance 677, passed February 18, 2026.

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b. At least one ADU is allowed within an existing multifamily dwelling. The total number of ADUs allowed is up to twenty-five percent of the existing multifamily dwelling units.

c. Not more than eight ADUs that are located on a lot that has an existing multifamily dwelling, but are detached from that multifamily dwelling and are subject to applicable height limits and four-foot rear and side setbacks. However, the number of ADUs allowable shall not exceed the number of existing units on the lot.

  - i. If an existing multifamily dwelling has a rear or side setback of less than four feet, no modification of the existing multifamily dwelling is required as a condition of approving an ADU. 

• d. Not more than two ADUs that are located on a lot that has a proposed multifamily dwelling, but are detached from that multifamily dwelling and are subject to applicable height limits and four-foot rear and side setbacks.

• C. Floor Area Requirements.

1. No ADU or JADU may be smaller than the size required to allow an efficiency unit pursuant to Health and Safety Code Section 17958.1, which is one hundred fifty square feet. The maximum size of an efficiency unit is five hundred square feet.

   2. The maximum size for a JADU is five hundred square feet.

   3. The maximum size for a newly constructed ADU is one thousand two hundred square feet.

   4. The floor area of an attached ADU shall not exceed fifty percent of the existing floor area of the main residence, unless necessary to accommodate at least an eight hundred square foot ADU.

   5. The conversion of an existing accessory structure or a portion of the existing primary residence to an ADU is not subject to unit size requirements.

   6. Garage and accessory structures ancillary to an ADU are not considered part of the ADU living area and are not included in the ADU floor area calculations.

• D. Exemptions From Maximum Floor Area Limitations.

1. The first eight hundred square feet of floor area of each ADU, attached and detached, and up to five hundred square feet for each JADU shall be excluded from maximum floor area calculations.

2. Additional floor area for each ADU may be excluded from maximum floor area calculations where staff determines the following conditions are met:

a. If a detached ADU meets and/or exceeds the minimum front, side, and rear setbacks of Chapter 17.40, Accessory Buildings and Structures, then the ADU will be allowed an additional floor area exemption beyond the first eight hundred square feet of floor area, up to a total of one thousand two hundred square feet.

The Atherton Municipal Code is current through Ordinance 677, passed February 18, 2026.

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• b. If an attached ADU is located in the main buildable area and encroaches into the side and rear yard setbacks by not more than twenty percent of the required setback, then the ADU shall be allowed an additional floor area exemption beyond the first eight hundred square feet of floor area, up to a total of one thousand two hundred square feet.

3. No floor area limitation shall be required for any conversion of an existing nonconforming building to an ADU.

4. No floor area limitation shall be required for conversions of portions of existing multifamily dwelling structures that are not used as livable space, including, but not limited to, storage rooms, boiler rooms, passageways, attics, basements, or garages, if each unit complies with state building standards for dwellings.

5. No floor area limitation shall be required for detached ADUs on a lot with an existing or proposed multifamily dwelling.

6. Interior stairs are exempt from floor area calculations if the stairs accommodate access to a new ADU located above an existing or proposed detached garage and if the entire structure or building complies with accessory structure or building setback requirements.

• E. Basements.

  1. Habitable basements are allowed under detached ADUs; however, these basements shall count toward the floor area of the ADU. An internal connection from the ADU to the habitable basement is required. No special structures permit is required for these basements.

  2. Habitable basements are allowed under attached ADUs; however, these basements shall count toward the floor area of the ADU if located outside the main building area setback. An internal connection from the ADU to the habitable basement is required.

3. Habitable basements are allowed under a JADU; however, these basements will be considered as the basement for the main residence and will not count toward the square footage of the JADU. No internal connection from the JADU will be allowed into the basement. Basements accommodating JADUs must be within the main building area.

4. Nonhabitable basements under ADUs are only allowed outside the accessory structure setback and are subject to the Heritage Tree Ordinance. Exterior access to the nonhabitable basement shall be located outside the accessory structure setback.

5. The floor area of an attached ADU or JADU does not count toward the basement allowance under section 17.44.030(A).

F. Setback Requirements. Except as specified below, all ADUs and JADUs shall comply with the setback requirements of the zone in which a unit is to be located.

1. JADUs shall have the same setbacks as required for the main residence.

The Atherton Municipal Code is current through Ordinance 677, passed February 18, 2026.

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2. A newly constructed detached or attached ADU that is eight hundred square feet or less on a lot with an existing or proposed single-family dwelling unit must be located at least four feet from a side or rear property line. This type of ADU does not have a front yard setback.

• a. No decks or mechanical equipment above six inches from grade are allowed in the four-foot side and rear setback.

3. A newly constructed attached ADU that has a floor area greater than eight hundred square feet and is located on a lot with an existing or proposed single-family dwelling unit shall be located in the main building area. These ADUs may encroach into side and rear yard setbacks by not more than twenty percent of the required setback.

4. A newly constructed detached ADU on a lot with an existing or proposed single-family dwelling unit that has a floor area greater than eight hundred square feet and is located on a lot with an existing or proposed single-family dwelling unit shall be located to maintain the setbacks for accessory buildings.

5. A newly constructed detached ADU that has a floor area greater than eight hundred square feet and is located on a lot with an existing or proposed single-family dwelling unit shall maintain the required separation distances between the proposed or existing main residence, accessory buildings and accessory structures as required in the accessory structures section of the zoning code.

6. A newly constructed detached ADU on a lot with an existing or proposed multifamily dwelling must be located at least four feet from a side or rear property line. This type of ADU does not have a front yard setback.

   • a. The required separation distances between the proposed or existing residence, accessory buildings and accessory structures as required in the accessory structure section of the zoning code, do not apply to this type of ADU.

7. Existing Structure. No setback shall be required for an existing living area or accessory structure or a structure constructed in the same location and to the same dimensions as an existing structure that is converted to an ADU or to a portion of an ADU. A setback of at least four feet from the side and rear lot lines is required for an accessory dwelling unit that is not converted from an existing structure or a new structure constructed in the same location and to the same dimensions as an existing structure.

8. For double frontage and corner lots, the front yard is the yard that is adjacent to the designated front property. The rear yard shall be the yard adjacent to the property line on the opposite side of the property from the designated front property line. The address for the ADU shall be on the street adjacent to the front yard.

G. Entrance Requirements. Any new attached ADU that is incorporated into a proposed or existing single-family dwelling unit and has a floor area greater than eight hundred square feet shall have a separate entrance facing the side or rear yard, where feasible. Any new detached ADU on a lot with an existing or proposed single-family dwelling unit that has a floor area greater than eight hundred square feet and/or uses the height allowed in subsection (H)(6) of this section, shall only have entrances facing towards the interior of the lot.

The Atherton Municipal Code is current through Ordinance 677, passed February 18, 2026.

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H. Height.

1. A maximum height of sixteen feet is allowed for a detached ADU on a lot with an existing or proposed single-family or multifamily dwelling.

2. A maximum height of eighteen feet is allowed for a detached accessory dwelling unit on a lot with an existing or proposed single-family or multifamily dwelling unit that is within one-half mile walking distance of a major transit stop or a high-quality transit corridor. An additional two feet in height to accommodate a roof pitch on the accessory dwelling unit that is aligned with the roof pitch of the primary dwelling unit is also allowed.

3. A maximum height of eighteen feet for a detached accessory dwelling unit on a lot with an existing or proposed multifamily, multistory dwelling.

4. A maximum height of twenty-five feet or the allowed height of the zoning district, whichever is lower, is allowed for an accessory dwelling unit that is attached to a primary dwelling.

5. Accessory dwelling units are limited to two stories, not including basements.

6. A maximum height of twenty-five feet is allowed for a detached ADU located above a garage; provided,

that:

• a. The total height is inclusive of the garage;

• b. The entirety of the garage structure or building, including any stairwell for the ADU, complies with the accessory structure setback requirements of the Zoning Code; and

• c. The ADU is accessed through a ground level entry vestibule and an interior stair.

d. The roofline shall be consistent with the style of the main residence. For example, a gabled roof form on the main residence shall require a gabled roof form on the ADU above garage.

e. If the second story floor area accommodating the ADU is less than the ground floor area, the residual roofing above the ground floor shall not accommodate a roof deck or balcony.

I. Heritage Tree Ordinance.

1. ADUs identified in subsection (B)(1), (B)(2)(a) or (B)(4) of this section are exempt from the Heritage Tree Ordinance pursuant to California Government Code Section 66323. However, if state law changes and enables the application of the Heritage Tree Ordinance to such ADUs, this exemption will cease immediately. In all other cases, the Heritage Tree Ordinance applies. The main residence and all other accessory buildings/ structures are subject to the Heritage Tree Ordinance.

2. ADUs not identified in subsection (B)(1), (B)(2)(a) or (B)(4) of this section may seek administrative exceptions to the Tree Protection Zone for a distance up to 6x in the R1-A zoning district. The Town Arborist will review such requests for ADUs, concurrently with review by Planning staff.

The Atherton Municipal Code is current through Ordinance 677, passed February 18, 2026.

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3. Any tree removal permitted by the Town in relation to the construction of an ADU must occur after the issuance of a related building permit. Such building permit must then adhere to time limits set forth in section 15.40.180. Penalties and remedies pursuant to section 8.10.070(B) may result in cases where trees are removed in relation to the approval of an ADU and the ADU is not constructed.

4. Expansion to Existing ADUs. If an existing ADU was previously exempt from the Heritage Tree Ordinance due to state law, as described above, and therefore resulted in the removal of a heritage tree, but is no longer exempt; then any expansion to the subject ADU must provide a replacement planting consistent with Chapter 8.10.

• J. Privacy, Screening and Landscaping.

1. New ADUs that are constructed above the ground floor and are not identified in subsection (B)(1), (B)(2)(a) or (B)(4) of this section, shall also be designed to reasonably preserve the privacy of adjacent property owners. Appropriate design techniques to preserve privacy include obscured glazing, the use of clerestory windows that are above eye level, screening treatments, locating windows toward the existing on-site residence, or providing no windows on facades facing adjacent properties.

2. Landscape screening for ADUs shall be installed to the greatest extent feasible for ADUs that are not identified in subsection (B)(1), (B)(2)(a) or (B)(4) of this section.

3. New ADUs that are constructed within the setbacks for accessory buildings and structures, as identified in section 17.40.040(A), may provide an eight-foot-high fence for screening. The fence shall be solid, opaque, and extend along the entire front, side or rear property line that is adjacent to the reduced setback area.

4. New ADUs that are constructed above a detached accessory garage must provide an eight-foot-high fence for screening. The required fence shall be solid, opaque and extend along the entire front, side or rear property line that is adjacent to the ADU. If the property line is already adequately screened with landscaping that is at least eight feet tall and opaque, then no new fencing is required.

5. No sidewall height limitations apply to ADUs.

K. Lighting Restrictions. Any lighting associated with ADUs that are not identified in subsection (B)(1), (B)(2)(a) or (B)(4) of this section shall be shielded or downlit and shall not shine onto adjoining properties, while meeting the minimum Building Code.

• L. Parking Requirements.

  1. No parking is required for a JADU.

  2. Unless subject to one of the exceptions immediately below, each ADU shall have assigned to it one parking space per ADU. These spaces may be provided as tandem parking on an existing driveway.

  3. No additional parking shall be required if one of the following conditions applies to the ADU:

     • a. The ADU is located within one-half mile walking distance of public transit.

The Atherton Municipal Code is current through Ordinance 677, passed February 18, 2026.

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• b. The ADU is located within an architecturally and historically significant district.

• c. The ADU is part of a proposed or existing primary residence or an existing accessory structure.

• d. On-street parking permits are required but not offered to the occupant of the ADU.

• e. A car share vehicle is located within one block of the ADU.

• f. When a permit application for an ADU is submitted with a permit application to create a new singlefamily dwelling or a new multifamily dwelling on the same lot; provided, that the ADU or the parcel satisfies any other criteria listed in this subsection.

4. When a garage, carport, or covered parking structure is demolished in conjunction with the construction of an ADU or converted to an ADU, off-street parking spaces do not need to be replaced.

5. A demolition permit for a detached garage that is to be replaced with an ADU shall be reviewed with the application for the ADU and issued at the same time.

M. ADU Rental and Ownership.

1. An ADU or JADU may be rented separate from the primary residence but must be rented for a period of longer than thirty days.

2. An ADU may not be sold or otherwise conveyed separate from the primary residence to a qualified buyer except when the ADU or primary dwelling was built or developed by a qualified nonprofit corporation, and meets the requirements pursuant to California Government Code Section 66341. JADUs may not be sold or otherwise conveyed separate from the primary residence to a qualified buyer in all instances.

• N. Owner Occupancy. The owner occupancy requirements detailed in this section shall apply to all lawfully permitted ADUs and JADUs within the Town on a single-family lot:

  1. ADUs and JADUs permitted before January 1, 2020. The owner-occupancy requirements applicable to the ADU or JADU at the time of its permitting shall apply.

  2. For ADUs and JADUs permitted on or after January 1, 2020, no owner-occupancy requirements shall apply.

• O. Passageways and Internal Connections.

1. No passageway, as defined in California Government Code Section 66313(j), that is unobstructed clear to the sky and extends from a street to one entrance of the ADU, shall be required in conjunction with the construction of an ADU or JADU.

2. Internal connections are allowed for attached ADUs and JADUs.

3. Internal connections are not allowed for detached ADUs to other accessory buildings, unless the

connection facilitates an interior stairwell that provides access to a detached ADU located above a garage.

The Atherton Municipal Code is current through Ordinance 677, passed February 18, 2026.

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This requirement does not apply to ADUs that are identified in subsection (B)(1), (B)(2)(a) or (B)(4) of this section.

P. Compliance With Applicable Requirements. ADUs and JADUs shall meet all applicable zoning and fire regulations and shall comply with local building codes. Fire sprinklers shall not be required for the ADU if they are not required for the primary residence. The construction of an accessory dwelling unit shall not trigger a requirement for fire sprinklers to be installed in the existing primary dwelling.

ance With Applicable Requirements._ ADUs and JADUs shall meet all applicable zoning and fire regulations and shall comply with local building codes. Fire sprinklers shall not be required for the ADU if they are not required for the primary residence. The construction of an accessory dwelling unit shall not trigger a requirement for fire sprinklers to be installed in the existing primary dwelling.

Q. Nonconforming Conditions. Nonconforming zoning conditions do not need to be corrected as part of an ADU or JADU approval. An ADU shall be approved regardless of nonconforming zoning conditions, building code violations, or unpermitted structures that do not present a threat to public health and safety and are not affected by the construction of the accessory dwelling unit.

R. Impact Fees. No impact fees will be charged on an ADU less than seven hundred fifty square feet. Any impact fees charged for an accessory dwelling unit of seven hundred fifty square feet or more shall be charged proportionately in relation to the square footage of the primary dwelling unit.

S. Utility Connections. A new ADU where there is an existing main residence shall not be required to have separate utility connections. A new ADU combined with a new house shall have separate utility connections. The connection may be subject to a connection fee or capacity charge that shall be 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 fee or charge shall not exceed the reasonable cost of providing this service.

T. Certificate of Occupancy. A certificate of occupancy for an accessory dwelling unit will only be issued after a certificate of occupancy is issued for the primary dwelling. However, a certificate of occupancy for an accessory dwelling unit, not including accessory dwelling units attached to the primary residence, shall be issued if San Mateo County is subject to a proclamation of a state of emergency by the Governor on or after February 1, 2025, and both of the following are met:

1. The primary dwelling was substantially damaged or destroyed by an event referenced in the state of emergency proclamation issued by the Governor.

2. The accessory dwelling unit has been issued construction permits and has passed all required inspections.

U. Enforcement. In enforcing building standards 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 for an accessory dwelling unit described in subsection (U)(1) or (U)(2) of this section, the Town of Atherton, upon request of an owner of an accessory dwelling unit for a delay in enforcement, shall delay enforcement of a building standard, subject to compliance with California Health and Safety Code Section 17980.12:

1. The accessory dwelling unit was built before January 1, 2020.

The Atherton Municipal Code is current through Ordinance 677, passed February 18, 2026.

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2. The accessory dwelling unit was built on or after January 1, 2020, in the Town of Atherton that, at the time the accessory dwelling unit was built, had a noncompliant accessory dwelling unit ordinance, but the ordinance is compliant at the time the request is made. (Ord. 675 § 4, 2025; Ord. 665 § 3, 2024)

A. General Submittal. A permit application for an ADU or JADU shall be considered and approved ministerially without discretionary review or a hearing, notwithstanding Section 65901 or 65906 of the California Government Code or any local ordinance regulating the issuance of variances or special use permits.

1. The Town shall determine whether an application to create or serve an ADU or JADU is complete and provide written notice of this determination to the applicant not later than fifteen business days after the Town received the application.

2. If the Town determines an application is incomplete, the Town shall provide the applicant with a list of incomplete items and a description of how the application can be made complete. The list and description shall be provided with the written notice required by subsection (A)(1) of this section.

3. After receiving a notice that the application was incomplete, an applicant may cure and address the items that are deemed to be incomplete by the Town.

4. In the review of an application submitted pursuant to subsection (A)(3) of this section, the permitting agency shall not require the application to include an item that was not included in the list required by subsection (A)(2) of this section.

5. If an applicant submits an application pursuant to subsection (A)(3) of this section, the Town shall determine whether the additional application has remedied all incomplete items listed in the determination issued pursuant to subsection (A)(2) of this section. This additional application is subject to the timelines and requirements specified in subsection (A)(1) of this section.

6. If the Town does not make a timely determination as required by this subsection, the application or resubmitted application shall be deemed to be complete for the purposes of this section.

7. The Town shall either approve or deny the application to create or serve an ADU or JADU within sixty days from the date the Town receives a completed application if there is an existing single-family or multifamily dwelling on the lot, unless either:

   • a. The applicant requests a delay, in which case the sixty-day time period is tolled for the period of the requested delay; or

b. If a permit application for an ADU or JADU is submitted along with a permit application to create a new primary residence, the Town may delay acting on the permit application for the ADU or JADU until the Town acts on the permit application to create the new primary residence. At such time the permit application for such ADU or JADU is considered, it will still be considered ministerially without

The Atherton Municipal Code is current through Ordinance 677, passed February 18, 2026.

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discretionary review or a public hearing, regardless of its having been submitted along with an application for a new primary residence.

8. If a completed application for an ADU or JADU that complies with the provisions of this chapter has not been approved or denied within sixty days, not including the exceptions of subsection (A)(7) of this section, the application shall be deemed approved.

• B. Preapproved Plan Submittal. The Town shall either approve or deny an application for a detached ADU using preapproved plans pursuant to California Government Code Section 65852.27 within thirty days from the date the Town receives a completed application, if the application utilizes either of the following:

  1. A plan for an ADU that has been preapproved by the Town pursuant to California Government Code Section 65852.27(a) within the current triennial California Building Standards Code rulemaking cycle.

  2. A plan that is identical to a plan used in an application for a detached ADU approved by the Town within the current triennial California Building Standards Code rulemaking cycle. (Ord. 675 § 4, 2025; Ord. 665 § 3, 2024)