Article 14 — Accessory Dwelling Units

The purpose of this article is to establish regulations governing the development of accessory dwelling units on residential zoned properties with a single-family dwelling within the Town of Los Altos Hills. The establishment of these regulations will encourage the construction of accessory dwelling units and contribute to the community's housing stock while ensuring that the new units are consistent with the semi-rural hillside character of the Town and do not create any significant impacts with regards to traffic flow or public safety. The regulations further promote and achieve the goals and policies in the Town's housing element within the general plan and comply with state laws related to accessory dwelling units, including California Government Code Section 66314 et seq.

(§ 2, Ord. 590, eff. August 21, 2020; § 1, Ord. 591, eff. October 17, 2020; Ord. 612, eff. 7/20/ 2024)

For purposes of this article, the following definitions apply:

Accessory dwelling unit means 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 primary residence. It shall include permanent provisions for living, sleeping, eating, cooking, and sanitation on the same parcel as the single-family or multifamily dwelling is or will be situated. An accessory dwelling unit also includes an efficiency unit and a manufactured home, as defined in Health and Safety Code Section 18007.

Floor area is the interior habitable area of an accessory dwelling unit, including basements and attics, but not including a garage or other non-habitable areas adjacent to the unit.

Junior accessory dwelling unit or efficiency unit means a dwelling unit that is up to 500 square feet in size and contained entirely within an existing primary dwelling unit that provides an efficiency kitchen and a separate exterior entrance, and may include separate sanitation facilities, or may share sanitation facilities with the existing structure.

Lot coverage is defined the same as, and is equivalent to, development area.

Primary dwelling unit means the single-family residence on the property and is the larger of the two if there is an existing accessory dwelling unit on the property.

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.

Secondary dwelling means the same as an accessory dwelling unit. (§ 2, Ord. 590, eff. August 21, 2020; § 1, Ord. 591, eff. October 17, 2020)

Accessory dwelling units are permitted on all residential properties and subject to the following general standards and requirements:

• (a) Type and Unit Size.

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Town of Los Altos Hills, CA

LOS ALTOS HILLS CODE

§ 10-1.1403

§ 10-1.1403

• (1) One accessory dwelling unit and one junior accessory dwelling unit are allowed on any lot with an existing or proposed single-family dwelling unit provided that the lot has adequate access to water and sewer or septic services, or as otherwise allowed per California Government Code Sections 66323(a)(1) and (2).

  • i. A junior accessory dwelling unit is not considered a separate or new dwelling unit for purposes of providing service for water, sewer, or power, including calculation of a connection fee.

• (2) The maximum size of a detached accessory dwelling unit that is a studio or with one bedroom is 850 square feet and the maximum size of an accessory dwelling unit with more than one bedroom is 1,000 square feet.

• (3) The maximum size of an attached accessory dwelling unit is 1,000 square feet or 50% of the primary dwelling's living area, whichever is less, provided that at least 800 square feet is allowed.

• (4) The maximum size of a junior accessory dwelling unit is 500 square feet.

• (5) The size limits specified in this subsection do not apply when an accessory dwelling unit is created via conversion of existing floor area in an existing structure.

• (b) Placement on the Lot. Applications for an accessory dwelling unit shall be ministerially reviewed and approved by the Planning and Building Departments as provided in Section 10-1.1406 of this article. However, an application for an accessory dwelling unit, excluding conversions of existing floor area, in any of the following locations shall be required to obtain a site development permit pursuant to Section 10-2.301:

  • (1) Areas encumbered by a recorded easement, including, but not limited to, access easements, conservation easements, general public easements, open space easements, pedestrian pathway easements and public utility easements;

  • (2) Areas with slopes that meet or exceed 30%;

  • (3) Areas within 25 feet of the top of a creek bank;

  • (4) Areas within a geotechnical or seismic hazard zone. Review and approval of a geotechnical and/or geologic report prepared by a licensed geotechnical engineer or registered civil engineer is required in order to locate a structure within a geotechnical or seismic hazard zone;

  • (5) Areas within the critical root zone of a heritage oak pursuant to Section 12-2.300. Review and approval of an arborist report prepared by a licensed or consulting arborist is required if a structure is proposed within the critical root zone of a heritage oak tree.

• (c) Occupancy.

  • (1) An accessory dwelling unit or junior accessory dwelling unit may be rented separately from the primary dwelling unit.

• (2) An accessory dwelling unit or junior accessory dwelling unit shall be rented for a period of no less than 31 days and cannot be occupied as a short-term rental unit, as defined under Section 10-1.1202.

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Town of Los Altos Hills, CA § 10-1.1403

ZONING AND SITE DEVELOPMENT

§ 10-1.1403

• (3) Accessory dwelling units and junior accessory dwelling units shall not be sold or otherwise conveyed separately from the primary dwelling on the property, unless the accessory dwelling unit or the primary dwelling was built or developed by a qualified nonprofit corporation, and all of the conditions set forth under Government Code Section 66341(b) — (e) have been satisfied.

• (d) Development Area and Floor Area.

  • (1) An accessory dwelling unit is allowed up to 800 square feet of development area beyond the maximum development area permitted pursuant to Section 10-1.502.

  • (2) An accessory dwelling unit is allowed up to 800 square feet of floor area beyond the maximum floor area permitted pursuant to Section 10-1.503.

  • (3) All accessory dwelling unit development area and floor area beyond the limits set by subsections (c)(1) and (2) of this section shall conform to the limits specified in Sections 10-1.502 and 10-1.503.

  • (4) The floor area limits specified in this subsection do not apply when an accessory dwelling unit is created via conversion of existing floor area.

• (e) Setbacks. An accessory dwelling unit shall comply with the following setback requirements:

  • (1) Setbacks for an accessory dwelling unit are as follows:

    • i. The front yard setback, which is measured from the edge of the property lines adjacent to the primary public or private street right-of-way or access easement, shall be 40 feet. This requirement shall not be construed to prohibit the construction of an accessory dwelling unit that is in compliance with other applicable requirements of this article.

  • (2) The setback from side and rear property lines shall be at least four feet;

  • (3) A setback from side and rear property lines of at least 30 feet is encouraged and can qualify the accessory dwelling unit for incentives pursuant to Section 10-1.1407;

  • (4) All portions of an accessory dwelling unit, include eave overhangs and other projections, shall meet the required setbacks.

• (f) Height.

  • (1) The maximum height of an attached accessory dwelling unit may be up to the maximum height for a primary dwelling unit pursuant to Section 10-1.504;

  • (2) The maximum height of a detached accessory dwelling unit shall be one story and 16 feet on a lot with an existing or proposed primary dwelling unit.

• (3) For detached accessory dwelling units on a lot with an existing or proposed primary dwelling that is within one-half of one mile walking distance of a major transit stop or a high-quality transit corridor as defined under Public Resources Code Section 21155, the maximum height shall be 18 feet, or 20 feet where necessary to accommodate a roof pitch on the accessory dwelling unit that is aligned with the roof pitch of the primary dwelling unit.

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Town of Los Altos Hills, CA § 10-1.1403

LOS ALTOS HILLS CODE

§ 10-1.1404

• (g) Parking and Access. An accessory dwelling unit shall comply with the following parking and site access requirements:

  • (1) Vehicular access to an accessory dwelling unit from the nearest public or private street shall be provided by a common driveway with the primary dwelling;

  • (2) No parking shall be required for an accessory dwelling unit or the primary dwelling unit if the accessory dwelling unit application is submitted with the application to create the primary dwelling unit, for any of the following:

    • i. When a garage, carport, or covered parking structure is demolished in conjunction with the construction of, or conversion to, an accessory dwelling unit;

    • ii. The accessory dwelling unit is located within one-half mile walking distance of public transit;

    • iii. The accessory dwelling unit is located within an architecturally and historically significant historic district;

    • iv. The accessory dwelling unit is converted from the proposed or existing floor area of the primary dwelling or an existing accessory structure;

    • v. When on-street parking permits are required but not offered to the occupant of the accessory dwelling unit;

    • vi. When the accessory dwelling unit is within one block of a car share vehicle;

• (3) No additional on-site parking shall be required for a primary dwelling unit for the construction of a junior accessory dwelling unit.

• (§ 2, Ord. 590, eff. August 21, 2020; § 1, Ord. 591, eff. October 17, 2020; Ord. 612, eff. 7/20/ 2024)

An accessory dwelling unit shall be reviewed and approved without discretionary review or a hearing. As part of the planning department's ministerial approval, the following objective design requirements shall be confirmed:

• (a) The design of the accessory dwelling unit shall be as follows:

  • (1) For a detached unit, it shall match the design of the primary dwelling by use of the same exterior wall materials, identified color tones, window types, door and window trims, roofing materials and roof pitch;

  • (2) For attached units, it shall be constructed so that the entire structure appears to be one dwelling by use of the same building form, color tones, window types, and window and door trims;

• (b) For detached units that are within 30 feet of a side or rear property line, the exterior entrance shall not face a side or rear property line;

• (c) Exterior wall colors and materials shall have a light reflectivity value (LRV) of 50 or less and roof materials shall have a light reflectivity value (LRV) of 40 or less;

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Town of Los Altos Hills, CA § 10-1.1404

ZONING AND SITE DEVELOPMENT

§ 10-1.1407

• (d) Exterior building light fixtures shall be shielded and downward facing, and limited to one exterior light fixture per exterior doorway, or the minimum necessary to comply with the California Building Standards Code.

• (§ 2, Ord. 590, eff. August 21, 2020; § 1, Ord. 591, eff. October 17, 2020; Ord. 612, eff. 7/20/ 2024)

An accessory dwelling unit shall be designed and constructed in compliance with all applicable requirements of the California Building Standards Code and local code amendments. In addition, the following requirements shall be confirmed:

• (a) An accessory dwelling unit shall include permanent provisions for living, sleeping, eating, cooking, and sanitation.

• (b) An accessory dwelling unit is only required to have fire sprinklers if they are required for the primary dwelling.

• (c) An accessory dwelling unit constructed with a new single-family dwelling on the same lot must be connected to the public sanitary sewer system or be connected to a private sewage disposal system that is deemed to be adequate by the Santa Clara County Department of Environmental Health.

• (d) All electrical and utility services to a new detached accessory dwelling unit shall be undergrounded.

• (e) If the existing primary dwelling on the property has overhead electrical and utility services, and no upgrades to the overhead service are required to serve the new accessory dwelling unit, then the utility service from the power pole to the primary dwelling is not required to be undergrounded.

• (§ 2, Ord. 590, eff. August 21, 2020; § 1, Ord. 591, eff. October 17, 2020)

Applications for an accessory dwelling unit must be submitted to the Building Department on a form and with information and materials as required by the Building Official and the Planning Director, and shall be approved or disapproved within 60 days after receiving the complete application. The applicant may request that the 60 day review period be waived. (§ 2, Ord. 590, eff. August 21, 2020; § 1, Ord. 591, eff. October 17, 2020)

• (a) If a detached accessory dwelling unit provides a side and rear yard setback of at least 30 feet and provides at least one additional on-site parking space, it shall be eligible for the following incentives:

  • (1) The maximum size of the unit shall be increased to 1,200 square feet, provided that the additional development area and floor area conform to the limits specified in Sections 10-1.502 and 10-1.503.

  • (2) The maximum building height shall be increased to one story and 19 feet.

• (b) If an attached accessory dwelling unit provides at least one additional on-site parking

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Town of Los Altos Hills, CA § 10-1.1407

LOS ALTOS HILLS CODE

§ 10-1.1409

space, it shall be eligible for the following incentive:

• (1) The maximum size of the unit shall be increased to 1,200 square feet, provided that the additional development area and floor area conform to the limits specified in Sections 10-1.502 and 10-1.503.

• (c) If a junior accessory dwelling unit provides one additional on-site parking space, it shall be eligible for the following incentive:

(1) The maximum size of the unit shall be increased to 650 square feet. (§ 2, Ord. 590, eff. August 21, 2020; § 1, Ord. 591, eff. October 17, 2020)

The City Council may establish and set by resolution all fees and charges, consistent with Government Code Sections 66314 et seq., and related provisions, as may be necessary to effectuate the purpose of this article.

(§ 2, Ord. 590, eff. August 21, 2020; § 1, Ord. 591, eff. October 17, 2020; Ord. 612, eff. 7/20/ 2024)

Owners of existing non-permitted accessory dwelling units which were constructed or otherwise in existence prior to December 31, 2019, may apply for a building permit to legalize the unit subject to conformance with the regulations in this article, the current California building standards code in effect at the time of the application, and such rules and regulations as may be adopted by resolution of the City Council. Notwithstanding the foregoing, an application for an accessory dwelling unit shall not be denied based on the correction 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. (§ 2, Ord. 590, eff. August 21, 2020; § 1, Ord. 591, eff. October 17, 2020; Ord. 612, eff. 7/20/ 2024)

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Town of Los Altos Hills, CA § 10-1.1501

ZONING AND SITE DEVELOPMENT

§ 10-1.1502