The intent of this chapter is to provide regulations to accommodate accessory and junior accessory dwelling units (ADU/JADU), in order to provide for variety to the city's housing stock and additional affordable housing opportunities. These units shall be separate, self-contained living units, with separate entrances from the main residence, whether attached or detached. The standards below are provided to minimize the impacts of units on nearby residents and throughout the city, and to assure that the size and location of such dwellings is compatible with the existing or proposed residence(s) on the site and with other structures in the area.

(Ord. 5656 § 2 (part), 2025: Ord. 5574 § 2 (part), 2023: Ord. 5507 § 3 (part), 2020)

The establishment of an accessory dwelling unit is permitted in zoning districts when single-family or multi-family residential is a permitted land use. The development of a single-family home, ADU, and/or a JADU on a lot that allows for single-family development shall not be considered a multi- family development pursuant to PAMC Section 18.04.030, nor shall they require architectural review pursuant to other sections of Chapter 18.

(Ord. 5656 § 2 (part), 2025: Ord. 5574 § 2 (part), 2023: Ord. 5507 § 3 (part), 2020)

   (a)   Government Code section 66323 provides that certain units shall be approved notwithstanding state or local regulations that may otherwise apply. The following types of units shall be governed by the standards in this section. In the event of a conflict between this section and Government Code section 66323, the Government Code shall prevail.

   1.   An ADU and JADU within the existing space of a single-family dwelling or an ADU within the existing space of an accessory structure (i.e. conversion without substantial addition).

   2.   An ADU and JADU within the proposed space of a single-family dwelling.

   3.   A detached, new construction ADU on a lot with a proposed or existing single-family dwelling, provided the ADU does not exceed 800 square feet, four-foot side and rear (i.e. interior) setbacks, or the maximum height described in subparagraph (A), (B), or (C) of paragraph (4) of subdivision (b) of Government Code Section 66321, as applicable.

   4.   ADUs created by conversion of portions of existing multi-family dwellings not used as livable space.

   5.   Up to eight detached ADUs on a lot with an existing multi-family dwelling, provided that the number of ADUs does not exceed the number of existing units on the lot.

   6.   Up to two detached ADUs on a lot with a proposed multi-family dwelling.

   (b)   The Development Standards for units governed by this section are summarized in Table 1. Regulations set forth in section 18.09.040 do not apply to units created under 18.09.030. The minimum and maximum sizes indicated in Table 1 do not prohibit units that are greater than 800 square feet. These sizes simply serve to distinguish when a unit transitions from regulations set forth in Table 1 and section 18.09.030 to regulations set forth in Table 2 and section 18.09.040.

 

   (c)   Development standards stated elsewhere in this Section or Title 18, including standards related to FAR, lot coverage, and privacy, are not applicable to ADUs or JADUs that qualify for approval under this section. When there is an ADU or JADU attached to an existing or proposed primary dwelling, the shared wall between these units shall contribute to the maximum allowable Floor Area, Lot Coverage, and Maximum House Size of the primary unit. For a single-family home, this measurement shall be taken to the outside stud wall in accordance with Section 18.04.030(a)(65)(D). For a multi-family dwelling, this measurement shall be taken to the outside surface of exterior walls in accordance with Section 18.04.030(a)(65)(B) and (C).

   (d)   The establishment of accessory dwelling units and junior accessory dwelling units pursuant to this section shall not be conditioned on the correction of non-conforming zoning conditions; provided, however, that nothing in this section shall limit the authority of the Chief Building Official to require correction of building standards relating to health and safety. Upon request of the owner for a delay in enforcement, the Chief Building Official shall delay enforcement of a building standard, subject to compliance with Section 17980.12 of the Health and Safety Code.

   (e)   The installation of fire sprinklers shall not be required in an accessory dwelling unit if sprinklers 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 multifamily dwelling. Nothing in this section shall preclude the Fire Marshal from accepting fire sprinklers as an alternative means of compliance with generally applicable fire protection requirements.

   (f)   Rental of any unit created pursuant to this section shall be for a term of 30 days or more.

   (g)   Attached units shall have independent exterior access from a proposed or existing single-family dwelling. Except for JADUs, attached units shall not have an interior access point to the primary dwelling (e.g. hotel door or other similar feature/appurtenance). If a permitted JADU does not include a separate bathroom, the permitted JADU shall include a separate entrance from the main entrance to the structure, with an interior entry to the main living area.

   (h)   Conversion of an existing accessory structure pursuant to Government Code section 66314(d)(7) may include reconstruction in-place of a non-conforming structure, so long as the renovation or reconstruction does not increase the degree of non-compliance, such as increased height, envelope, or further intrusion into required setbacks. An expansion of not more than 150 square feet beyond the same physical dimensions as the existing accessory structure may be provided to accommodate ingress and egress. Any addition to the existing accessory structure that is not limited to providing for ingress and egress to the unit, and that exceeds the envelope of the existing accessory structure shall be subject to Section 18.09.040.

   (i)   Street addresses shall be assigned to all units prior to building permit final to assist in emergency response.

   (j)   The unit shall not be sold separately from the primary residence, except as allowed under Government Code Section 66341.

   (k)   Replacement parking is not required when an off-street parking space is converted to, or demolished in conjunction with the construction of, an ADU.

   (l)   JADUs shall comply with the requirements of Section 18.09.050.

(Ord. 5656 § 2 (part), 2025: Ord. 5585 § 2 (part), 2023: Ord. 5574 § 2 (part), 2023: Ord. 5507 § 3 (part), 2020)

   (a)   This section shall govern applications for ADUs that do not qualify for approval under Section 18.09.030 and for which the city may impose local standards pursuant to Government Code section 66314. Nothing in this section shall be interpreted to prohibit an ADU of up to 800 square feet, at the heights stated in Table 2, with a four foot side and rear setbacks.

   (b)   The Development Standards for units governed by this section are provided in Table 2. These regulations do not limit the height of existing structures converted into ADUs unless the envelope of the building is proposed to be modified beyond any existing legal, non-conforming condition.

 

   (c)   A single-family or multi-family dwelling shall exist on the lot or shall be constructed on the lot in conjunction with the construction of an ADU.

   (d)   ADU square footage shall not be included in FAR, lot coverage, and maximum house size calculations for a lot with an existing or proposed single family home, up to the amounts stated in Table 2. ADU square footage in excess of the exemptions provided in Table 2 shall be included in FAR, lot coverage, and maximum house size calculations for the lot.

   (e)   When there is an ADU attached to an existing or proposed primary dwelling, the shared wall between these units shall contribute to the maximum allowable Floor Area, Lot Coverage, and Maximum House Size of the primary unit. For a single-family home, this measurement shall be taken to the outside stud wall in accordance with Section 18.04.030(a)(65)(D). For a multi-family dwelling, this measurement shall be taken to the outside surface of exterior walls in accordance with Section 18.04.030(a)(65)(B) and (C).

   (f)   Attached units shall have independent exterior access from a proposed or existing single-family dwelling. Attached units shall not have an interior access point to the primary dwelling (e.g. hotel door or other similar feature/appurtenance).

   (g)   Reserved.

   (h)   For properties listed in the California Register of Historical Resources, compliance with the appropriate Secretary of Interior's Standards for the Treatment of Historic Properties shall be required.

   (i)   Noise-producing equipment such as air conditioners, water heaters, and similar service equipment that exclusively serves an ADU may be located anywhere on the site, provided they maintain the underlying front yard setback requirements of the property and, if the property is a corner lot, a 10-foot street-side setback. All such equipment shall be insulated and housed, except that the Director may permit installation without housing and insulation, provided that a combination of technical noise specifications, location of equipment, and/or other screening or buffering will assure compliance with the city's Noise Ordinance at the nearest property line. All service equipment must meet the city's Noise Ordinance in Chapter 9.10 of the Municipal Code.

   (j)   Setbacks

      1.   Detached units shall maintain a minimum three-foot distance from the primary unit, measured from the exterior walls of structures.

      2.   A basement or other subterranean portion that serves an ADU may encroach into a setback required for the primary dwelling provided the following conditions are met:

         (A)   Newly constructed basement walls are no closer than four feet to an adjacent interior side or rear property line.

         (B)   A new lightwell associated with a basement shall not be placed closer than four feet to an adjacent interior property line. When visible from the right of way, these facilities shall be screened from view with vegetation.

         (C)   Habitable ADU basements shall contribute toward the unit’s total allowable floor area. Any floor area in excess of the exemptions provided in this Section shall contribute to the total allowable limits for the site.

      3.   Projections, including but not limited to windows, doors, mechanical equipment, venting or exhaust systems, are not permitted to encroach into the required setbacks, with the exception of a roof eave of up to two feet.

      4.   For corner lots developed as a single-family home, when an existing or proposed primary dwelling unit is expanded or constructed simultaneously with the construction of a new ADU, the homeowner may elect to build all structures to a 10-foot street-side setback and a 16-foot front yard setback, regardless of the presence of a more restrictive special setback, unless a fire or life-safety regulation requires a greater setback. Pursuant to Government Code section 66321(b)(3), a street-side setback may not preclude the development of an 800 square foot unit.

      5.   When an existing, legal, nonconforming structure is converted or reconstructed to create an ADU, any portion of the ADU that is in the same location and falls within the building envelope of the original structure shall not be subject to the development standards stated in this Section. Any portion of the ADU that is in a different location or exceeds the envelope of the original structure shall comply with the development standards stated in this Section.

      6.   Notwithstanding the development standards stated in Table 2 and paragraph (5) above, when an existing, legal, non-conforming structure is converted in place to an ADU, the envelope of the structure may be modified to encroach further into a setback or daylight plane as follows:

         (A)   The height of the existing structure may be increased by no more than one linear foot in height commensurate to the existing roofline of the structure provided the height of the addition does not exceed 12 feet from grade. The roofline shall not be changed to a style other than what currently exists on the structure.

         (B)   Each non-conforming wall may be expanded by no more than six inches in thickness based on its existing location and configuration, as measured to exterior surface of the material, to provide for greater insulation and energy requirements provided that a minimum of one foot is maintained between the addition and an adjacent interior property line. An existing wall of a structure that does not currently have a separation of one foot from a parallel property line shall not be expanded outward.

         (C)   All other additions not specified here shall follow the standard setbacks for the ADU identified in Table 2.

   (k)   Design

      1.   Except on corner lots, where feasible, the unit shall not have an entranceway facing the same lot line (property line) as the entranceway to the main dwelling unit unless the entranceway to the accessory unit is located in the rear half of the lot. Exterior staircases to second floor units shall be located toward the interior side or rear yard of the property.

      2.   Privacy

         (A)   Second story doors and decks shall not face a neighboring property line. Second story decks and balconies shall utilize screening barriers to prevent views towards an adjacent interior property line. These barriers shall be a minimum five-foot, six-inch height, from the floor level of the deck or balcony and shall not include perforations of any kind that would allow visibility between properties.

         (B)   Windows on a second floor, loft, or equivalent elevated space, excluding those required for egress, shall have a five-foot sill height as measured from the second-finished floor level, or utilize opaque glazing on the entirety of any window that faces an adjacent interior property line.

         (C)   Windows on a second finished floor, loft, or equivalent elevated space, shall be offset from neighbor's windows to maximize privacy.

         (D)   Where feasible, egress windows on the first and second finished floor of an ADU shall not face towards an adjacent interior property line. If this is not feasible, then these windows shall utilize opaque glazing on the whole window.

         (E)   If the first finished floor of an ADU is two feet or more above grade, then first floor windows shall include the following:

            i.   Non-egress, operable windows facing an adjacent interior property line shall have a windowsill(s) that start five feet above the first finished floor for the unit;

            ii.   Non-egress, non-operable windows facing an adjacent interior property line shall have the lower half of window(s) (minimum of five feet above the first finished floor) utilize opaque glazing.

         (F)   Where feasible, the use of skylights (whether operable or not) shall be used in lieu of operable windows that face adjacent interior properties.

         (G)   No exterior lighting shall be mounted above seven feet. All lighting mounted on walls shall be directed downwards and shall not direct light towards adjacent interior property lines. Any ground lighting shall not direct light upwards to the building or sky.

   (l)   Parking

      1.   Replacement parking is not required when a garage, carport, covered parking structure, or uncovered parking space is converted to, or demolished in conjunction with the construction of, an ADU.

      2.   When parking is provided, the unit shall have street access from a driveway in common with the main residence in order to prevent new curb cuts, excessive paving, and elimination of street trees, unless separate driveway access will result in fewer environmental impacts such as paving, grading or tree removal.

      3.   When a single-family dwelling unit is permitted simultaneously with the construction of new ADUs, the primary unit’s covered parking requirements identified in Chapter 18.10 and 18.12 do not need to be provided. Two uncovered parking spaces shall be provided in any configuration on the lot including within the front or street-side setback for the property.

      4.   If covered parking for a unit is provided in any district, the maximum size of the covered parking area for the accessory dwelling unit is 220 square feet. This space shall count towards the total floor area for the site but does not contribute to the maximum size of the unit. Any attached garage shall not have an interior access point to the ADU (e.g. hotel door or other similar feature/appurtenance).

   (m)   Landscape

      1.   For the purposes of this subsection (m), “protected tree” means:

         (A)   Any locally native tree of the species Acer macrophyllum (Bigleaf Maple), Calocedrus decurrens (California Incense Cedar), Quercus agrifolia (Coast Live Oak), Quercus douglasii (Blue Oak), Quercus kelloggii (California Black Oak), or Quercus lobata (Valley Oak) which is eleven and one-half inches in diameter (thirty-six inches in circumference) or more when measured four and one-half feet (fifty-four inches) above natural grade.

         (B)   Any Coast Redwood tree (species Sequoia sempervirens) that is eighteen inches in diameter (fifty-seven inches in circumference) or more when measured four and one-half feet (fifty-four inches) above natural grade.

         (C)   Any tree of any species, other than a Coast Redwood Tree, fifteen inches in diameter (forty-seven inches in circumference) or more when measured four and one-half feet (fifty-four inches) above natural grade. A “protected tree” does not include a tree of any species on the Exempt Species List put forth by the Department of Urban Forestry and available on the City’s website.

         (D)   Any tree designated for protection during review and approval of a current or previously completed development project.

         (E)   Any tree designated for carbon sequestration and storage and/or environmental mitigation purposes as identified in an agreement between the property owner and a responsible government agency or recorded as a deed restriction.

         (F)   Any heritage tree previously designated by the city council.

         (G)   Any tree previously planted as a replacement mitigation tree.

      2.   Except as provided in subsection (3) below, the construction of an ADU shall not impact any protected tree, on the subject property or any adjacent lot by requiring:

         (A)   Removal of more than twenty-five percent of the functioning leaf, stem, or root area of a tree in any twenty-four-month period; or

         (B)   Removal of more than fifteen percent of the functioning root area of any Quercus (oak) species in any thirty-six-month period; or

         (C)   Trenching, excavating, altering the grade, or paving within the tree protection zone of a tree in a way that foreseeably leads to the death of the tree. For the purposes of this subsection (m), "tree protection zone" means the area defined by a circle with a radius ten times the diameter of the trunk when measured four and one-half feet (fifty-four inches) above natural grade.

      3.   If an action prohibited by section 18.09.040(m)(2) is necessary to allow the construction of an ADU that meets the minimum standards set forth in state law, the tree shall be replaced according to the objective requirements identified in the Tree Canopy Replacement Table of the Palo Alto Tree and Landscape Technical Manual.

      4.   The construction of an ADU must comply with applicable objective standards and specifications in the Tree and Landscape Technical Manual for the protection of trees during construction. Compliance with this subsection (4) shall not delay or cause the denial of an ADU or JADU building permit or use permit.

   (n)   Miscellaneous requirements

      1.   Street addresses shall be assigned to all units prior to building permit final to assist in emergency response.

      2.   The unit shall not be sold separately from the primary residence except as allowed under Government Code Section 66341.

      3.   Rental of any unit created pursuant to this section shall be for a term of 30 days or more.

      4.   The installation of fire sprinklers shall not be required in an accessory dwelling unit if sprinklers are not required for the primary residence. Nothing in this section shall preclude the Fire Marshal from accepting fire sprinklers as an alternative means of compliance with generally applicable fire protection requirements.

(Ord. 5656 § 2 (part), 2025: Ord. 5585 § 2 (part), 2023: Ord. 5574 § 2 (part), 2023: Ord. 5557 § 6, 2022: Ord. 5507 § 3 (part), 2020)

   (a)   A JADU may be created on a lot in a single-family residential zone with an existing or proposed single family residence. A JADU shall be attached to or created within the walls of an existing or proposed primary dwelling, including enclosed uses within the residence, such as an attached garage.

   (b)   The JADU shall include an efficiency kitchen, requiring the following components: A cooking facility with appliances, and; food preparation counter and storage cabinets that are of reasonable size in relation to the size of the junior accessory dwelling unit.

      1.   JADUs may share sanitation facilities (bathrooms, laundry facilities, etc.) with the primary unit. If a permitted JADU does not include a separate bathroom, the permitted junior accessory dwelling unit shall include a separate entrance from the main entrance to the structure, with an interior entry to the main living area. In this instance, the floor area and lot coverage associated with shared space shall count towards the primary unit’s maximum allowances only. The combined sanitation facilities between the units shall include shower, toilet, and sink fixtures at a minimum and shall conform to the minimum requirements specified in the Building Code.

   (c)   For the purposes of any fire or life protection ordinance or regulation or for the purposes of providing service for water, sewer, or power, a JADU shall not be considered a separate or new unit.

   (d)   The owner of a parcel proposed for a JADU shall occupy as a primary residence either the primary dwelling or the JADU. Owner-occupancy is not required if the owner is a governmental agency, land trust, or housing organization.

   (e)   Prior to the issuance of a building permit for a JADU, the owner shall record a deed restriction in a form approved by the city that includes a prohibition on the sale of the junior accessory dwelling unit separate from the sale of the single-family residence, requires owner-occupancy consistent with subsection (d) above, and restricts the size and attributes of the JADU to those that conform with this section.

   (f)   JADU incentive. The existing or proposed primary dwelling unit shall be afforded bonus square footage equal to the square footage of a proposed JADU when a JADU is constructed on site, provided the JADU meets the following requirements:

      1.   The JADU must conform to the underlying zoning district’s development standards for single family homes.

      2.   The maximum number of units on site shall not exceed four (two ADUs, one JADU, and one primary home).

      3.   The maximum size of the JADU shall not exceed 500 square feet.

      4.   The total maximum bonus/exempt floor area provided for the site under Section 18.09.040 and 18.09.050 may not exceed 800 square feet.

      5.   The exterior entryway to the JADU shall not face the same direction as the entrance to the primary home.

      6.   All egress windows which face an adjacent residential property must utilize opaque glazing on the whole window.

      7.   All non-egress windows which face an adjacent residential property must have a windowsill(s) that start five feet above the first finished floor for the unit.

      8.   All noise producing equipment associated with the JADU must comply with the noise regulations in PAMC 9.10.

(Ord. 5656 § 2 (part), 2025: Ord. 5585 § 2 (part), 2023: Ord. 5574 § 2 (part), 2023: Ord. 5507 § 3 (part), 2020)