Pursuant to the provisions of Government Code Sections 66310 et seq., the following requirements apply to _accessory_ _dwelling_ _units_ and junior _accessory_ _dwelling_ _units_, as specified:

_Accessory_ _Dwelling_ _Units_. _Accessory_ _dwelling_ _units_ are allowed on a legal lot, as defined by Section 18.08.340 of this title, that is zoned RS, RM, RC, AP, AW or PD, or is developed under the provisions of the :AH overlay zone, and that contains an existing or proposed single family _dwelling_ or an existing or proposed multifamily _unit_ that is precluded from transient occupancy.

Junior _Accessory_ _Dwelling_ _Units_. Only one junior _accessory_ _dwelling_ _unit_ is permitted on a legal lot, as defined by Section 18.08.340 of this title, that is zoned RS, RM, RC, AP, AW or PD, or is developed under the provisions of the :AH overlay zone, and that contains an existing or proposed single family _dwelling_.

Urban Lot Splits. No _accessory_ _dwelling_ _unit_ or junior _accessory_ _dwelling_ _unit_ shall be permitted if the lot was created by an urban lot split pursuant to Chapter 17.17, and the approval of the _accessory_ _dwelling_ _unit_ or junior _accessory_ _dwelling_ _unit_ would result in more than two _dwelling_ _units_ on the lot.

Types of _Accessory_ _Dwelling_ _Units_. _Accessory_ _dwelling_ _units_ may be attached to an existing or proposed primary structure or _accessory_ structure (attached _accessory_ _dwelling_ _unit_), detached from an existing or proposed primary structure (detached _accessory_ _dwelling_ _unit_), or located within an existing primary structure or existing _accessory_ building (interior _accessory_ _dwelling_ _unit_).

Junior _Accessory_ _Dwelling_ _Units_. Junior _accessory_ _dwelling_ _units_ must be created within the walls of an existing or proposed primary _dwelling_. An attached garage is part of the single-family _dwelling_ _unit_ for purposes of this Section 18.104.180. Junior _accessory_ _dwelling_ _units_ are only permitted on a legal lot with no more than one existing or proposed single-family _dwelling_.

Exempt _Accessory_ _Dwelling_ _Units_. The following are exempt from certain development and design standards, as specified in subsections B and C below, and are referred to as "exempt _accessory_ _dwelling_ _units_":

One _accessory_ _dwelling_ _unit_ on a legal lot with up to one junior _accessory_ _dwelling_ _unit_ and a proposed or existing single-family _dwelling_ if the _accessory_ _dwelling_ _unit_ and junior _accessory_ _dwelling_ _unit_ comply with the following:

The _accessory_ _dwelling_ _unit_ is within the proposed or existing space of a single-family _dwelling_ or existing space of an _accessory_ structure and may include an expansion of not more than one hundred and fifty square feet beyond the same physical dimensions as the existing _accessory_ structure. An expansion beyond the physical dimensions of the existing _accessory_ structure shall be limited to accommodating ingress and egress.

The _accessory_ _dwelling_ _unit_ has separate exterior access from the proposed or existing single-family _dwelling_.

The junior _accessory_ _dwelling_ _unit_ complies with the requirements of this subsection A and subsection D below.

One detached, new construction _accessory_ _dwelling_ _unit_ on a legal lot with a proposed or existing single-family _dwelling_ if the _accessory_ _dwelling_ _unit_ provides four-foot side and rear yard setbacks; does not exceed eight hundred square feet in floor area, and does not exceed the height described in subsection A.4.b.i or ii, as applicable.

Eighteen feet on a legal lot with an existing or proposed single-family _dwelling_ if the lot is within one-half mile walking distance of a major transit stop or a high-quality transit corridor, as those terms are defined in Public Resources Code Section 21155. An additional two feet in height may be permitted to accommodate a roof pitch on the _accessory_ _dwelling_ _unit_ that is aligned with the roof pitch of the single-family _dwelling_;

Up to two detached _accessory_ _dwelling_ _units_ on a legal lot with a proposed or existing multifamily _dwelling_ if the _accessory_ _dwelling_ _units_ provide at least four-foot side and rear yard setbacks. If the existing multifamily _dwelling_ has a rear or side setback of less than four feet, no modification of the existing multifamily _dwelling_ shall be required as a condition of approving the application to construct an _accessory_ _dwelling_ _unit_ that satisfies the requirements of this subsection. The height of the _accessory_ _dwelling_ _units_ shall not exceed the following:

Eighteen feet on a legal lot with an existing or proposed multifamily _dwelling_ _unit_ if the lot is within one-half mile walking distance of a major transit stop or a high-quality transit corridor, as those terms are defined in Public Resources Code Section 21155. An additional two feet in height may be permitted to accommodate a roof pitch on the _accessory_ _dwelling_ _unit_ that is aligned with the roof pitch of the multifamily _dwelling_;

A legal lot with an existing multifamily _dwelling_ may contain _accessory_ _dwelling_ _units_ converted from portions of the building that are not used as livable space, if each _unit_ complies with state building standards for _dwellings_. The number of _accessory_ _dwelling_ _units_ permitted is equivalent to up to 25 percent of the number of existing, legally permitted _units_ in the multifamily _dwelling_, or one, whichever is greater.

Only one _accessory_ _dwelling_ _unit_ shall be permitted on legal lots with proposed or existing single-family or multifamily _dwellings_ unless all existing and proposed _accessory_ _dwelling_ _units_ on the lot meet the requirements of subsection A.4 above.

Building Code. Junior _accessory_ _dwelling_ _units_ and _accessory_ _dwelling_ _units_ shall comply with all applicable building code requirements, except as follows:

Fire sprinklers shall not be required for an _accessory_ _dwelling_ _unit_ if they are not required for the primary _dwelling_. Fire sprinklers may not be required for an existing primary _dwelling_ _unit_ as a condition of the approval of an _accessory_ _dwelling_ _unit_.

The new construction of an _accessory_ _dwelling_ _unit_ shall not constitute a Group R occupancy change under the local building code, as described in Section 310 of the California Building Code (Title 24 of the California Code of Regulations), unless the building official or enforcement agency makes a written finding based on substantial evidence in the record that the construction of the _accessory_ _dwelling_ _unit_ could have a specific, adverse impact on public health and safety or the _accessory_ _dwelling_ _unit_ is converted from unhabitable or nonresidential space.

Owner Occupancy. On a property with a junior _accessory_ _dwelling_ _unit_, the owner must occupy as a principal residence either the primary _dwelling_ or the junior _accessory_ _dwelling_ _unit_, unless the owner is another governmental agency, land trust, or housing organization. Owner occupancy is not required for the _accessory_ _dwelling_ _unit_.

_Accessory_ _Dwelling_ _Unit_. An _accessory_ _dwelling_ _unit_ may not be sold separately from the single-family or multifamily _dwelling_, except that the _accessory_ _dwelling_ _unit_ and primary _unit_ may be owned by multiple owners as tenants in common if the single-family _dwelling_ and _accessory_ _dwelling_ _unit_ were developed by a qualified nonprofit, as that term is defined in Government Code Section 66340, and if all of the provisions of Government Code Section 66341 are met.

Junior _Accessory_ _Dwelling_ _Unit_. A junior _accessory_ _dwelling_ _unit_ may not be sold separately from the single-family _dwelling_.

_Accessory_ _Dwelling_ _Units_. At the time of application for an _accessory_ _dwelling_ _unit_, the property owner shall acknowledge in writing that neither the _accessory_ _dwelling_ _unit_ nor the single-family _dwelling_ or multifamily _dwelling_ may be used for short-term residential rentals of less than thirty days. Prior to the issuance of a building permit for the _accessory_ _dwelling_ _unit_, the owner shall record a covenant with the Napa County Recorder's Office in a form approved by county counsel to prohibit renting the _accessory_ _dwelling_ _unit_ for fewer than thirty consecutive calendar days.

Junior _Accessory_ _Dwelling_ _Units_. Prior to issuance of a certificate of occupancy for a junior _accessory_ _dwelling_ _unit_, the owner shall record a covenant in a form prescribed by county counsel, which shall run with the land and provide for the following:

A prohibition on the sale of the junior _accessory_ _dwelling_ _unit_ separate from the sale of the single-family principal _dwelling_;

A restriction on the size and attributes of the junior _accessory_ _dwelling_ _unit_ consistent with subsection D below;

A requirement that either the primary residence or the junior _accessory_ _dwelling_ _unit_ be the owner's bona fide principal residence, unless the owner is a governmental agency, land trust, or housing organization.

Development Standards - All _Accessory_ _Dwelling_ _Units_. The following development standards apply to all _accessory_ _dwelling_ _units_:

Except as specified below, an _accessory_ _dwelling_ _unit_ shall comply with the requirements of this Section 18.104.180, the underlying zoning district, and other provisions of the Napa County Code except:

If the requirements of the underlying zoning district or other provisions of the Napa County Code are inconsistent with the provisions of this Section 18.104.180, the standards of this section shall apply. Exempt _accessory_ _dwelling_ _units_ described in subsection A.4 need only comply with the applicable provisions of this Section 18.104.180, building code requirements, and health and safety requirements, such as those applicable to private water and sewer service.

Limits on lot coverage, front yard setback, floor area ratio, open space, and size must permit or shall be waived to allow an eight hundred square foot detached or attached _accessory_ _dwelling_ _unit_ with four-foot side and rear yard setbacks, if the proposed _accessory_ _dwelling_ _unit_ is in compliance with all other applicable development standards.

The county may not require as a condition of approval the correction of nonconforming zoning conditions.

If the application is to legalize an unpermitted _accessory_ _dwelling_ _unit_ that was constructed before January 1, 2018, the _accessory_ _dwelling_ _unit_ does not need to conform with this section or building standards pursuant to Health & Safety Code Section 17960 et seq. However, the county may deny the application for an unpermitted _accessory_ _dwelling_ _unit_ constructed before January 1, 2018 if the building official makes a finding that correcting the violation is necessary to protect the health and safety of the public or occupants of the structure.

No setback is required for a new structure constructed in the same location and to the same dimensions as an existing structure.

Entrance. An _accessory_ _dwelling_ _unit_ shall have a separate entrance from the primary _dwelling_ _unit_.

Parking. _Accessory_ _dwelling_ units shall have one parking space per _unit_, except that studio units shall not require a parking space. These spaces may be provided as tandem parking on an existing driveway. Off-street parking is permitted in setback areas or through tandem parking, unless specific findings are made that parking in setback areas or tandem parking is not feasible based upon fire and life safety conditions. "Tandem parking" means that two or more automobiles are parked on a driveway or in any other location on a lot, lined up behind one another. Notwithstanding the foregoing, no parking shall be required in any of the following instances:

The _accessory_ _dwelling_ _unit_ is located within one-half mile of a public transit stop 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;

The _accessory_ _dwelling_ _unit_ is located within an architecturally and historically significant district;

On-street parking permits are required but not offered to the occupant of the accessory dwelling unit; or

Demolition of Parking. If the construction of an accessory dwelling unit replaces an existing garage, carport, or covered parking structure, no replacement spaces need be provided. If the applicant applies for a demolition permit to demolish a detached garage and a building permit to construct a detached accessory dwelling unit, the demolition permit and building permit for the accessory dwelling unit shall be issued at the same time.

Maximum Height: The height of a detached accessory dwelling unit shall not exceed thirty-five feet except that exempt accessory dwelling units are subject to the height limits in subsection A.4.

Maximum Size. The total floor space of a detached accessory dwelling unit shall not exceed one thousand two hundred square feet as measured from the inside of the exterior walls except the exempt accessory dwelling units are subject to limits on size contained in subsection A.4.

Setbacks. A four feet setback is required from the rear and side property lines.

Maximum Height. The height of an attached accessory dwelling unit shall not exceed thirty-five feet or the height limitation that applies to the single-family dwelling or multifamily dwelling, whichever is lower. However, the accessory dwelling unit may not exceed two stories.

Setbacks. A four feet setback is required from the rear and side property lines.

Interior Access. An accessory dwelling unit attached to an accessory structure shall not have interior access connecting to the accessory structure.

Design Standards - Non-Exempt Accessory Dwelling Units. The following design standards shall apply to all accessory dwelling units except exempt accessory dwelling units described in subsection A.4:

Detached Units: Maximum Distance Between Units. The maximum distance that a detached accessory dwelling unit may be from the nearest portion of the living area of the existing legal single-family dwelling or multi-family dwelling on the same legal lot shall be five hundred feet, measured along a level, horizontal straight line, unless a greater distance is required to avoid an agricultural constraint or to meet the standards of the department relating to private water or sewer systems or to avoid an environmentally sensitive area as defined by Section 18.08.270 of this title.

The accessory dwelling unit shall be located no more than twenty feet from the living area of the existing dwelling and shall be attached to the existing dwelling in the manner set forth in Section 18.08.070 of this title.

Maximum size. The total floor space of an attached accessory dwelling unit shall not exceed one thousand two hundred square feet as measured from the inside of the exterior walls. If there is an existing primary dwelling, the total floor area of an attached accessory dwelling unit shall not exceed fifty percent of the existing primary dwelling or eight hundred square feet, whichever is greater.

Design and Development Standards - Junior Accessory Dwelling Units. Pursuant to the provisions of Government Code Sections 66310 et seq., the following requirements apply to all junior accessory dwelling units:

Size. The total floor space of a junior accessory dwelling unit shall not exceed five hundred square feet as measured from the inside of the exterior walls.

Entrance. An exterior entry separate from the exterior entry for the single-family dwelling unit shall be provided to serve a junior accessory dwelling unit. However, if the junior accessory dwelling unit shares sanitation facilities with the single-family dwelling unit, there must also be an interior entry to the main living area of the single-family dwelling unit.

Kitchen. The junior accessory dwelling unit shall include at least an efficiency kitchen which includes cooking appliances, a food preparation counter and storage cabinets that are of reasonable size in relation to the size of the junior accessory dwelling unit.

Parking. Parking is not required for a junior accessory dwelling unit. If the construction of a junior accessory dwelling unit replaces an existing attached garage, replacement parking is required.

Applications and Processing. All reviews of accessory dwelling units and junior accessory dwelling units shall be ministerial.

In addition to other information requested in this section and the application form, for issuance of a building permit, the approval by the relevant department must be obtained where a private or individual sewage disposal system or water system is to be used.

The director shall administratively review and approve or deny complete ministerial permit applications for accessory dwelling units and junior accessory dwelling units within sixty days from the date the county receives a completed application, except that applications for pre-approved accessory dwelling unit plans shall be approved or denied within thirty days from the date that the county receives a completed application. However, if the permit application is submitted with an application to construct a new single-family or multifamily dwelling, then the county may delay review of the permit application for the accessory dwelling unit or junior accessory dwelling unit until the county approves or denies the permit for the new dwelling. If the application is denied, the director will provide, within the review period, a complete list of the application's deficiencies and describe how the applicant can remedy the application.

Fees and Utility Connections for Accessory Dwelling Units. All permit and mitigation fees and other charges applicable to primary dwellings in the zone in which the property is located shall apply to an accessory dwelling units except:

Accessory dwelling units shall not be considered new residential uses for the purposes of calculating any connection fees or capacity charges for utilities, including water and sewer service, unless the accessory dwelling unit is constructed with a new single-family dwelling.

Interior accessory dwelling units are exempt from any requirement to install a new or separate utility connection and to pay any associated connection or capacity fees or charges, unless the interior accessory dwelling unit was constructed with a new single-family dwelling. For other accessory dwelling units, new or separate utility connections are required between the accessory dwelling unit and the utility. Any connection or capacity charge shall be proportionate to the burden of the proposed accessory dwelling unit on the water or sewer system, based on either its square feet or the number of drainage fixture units.

No impact fees shall be imposed upon the development of an accessory dwelling unit less than seven hundred fifty square feet. Any impact fees charged for an accessory dwelling unit of seven hundred fifty feet or more shall be charged proportionately in relation to the square footage of the primary dwelling unit. For purposes of this provision, an "impact fee" includes the fees specified in Government Code Sections 66000 and 66477. Impact fees do not include connection fees or capacity charges.

For the purposes of providing service for water, sewer, or power, a junior accessory dwelling unit is not considered a separate or new dwelling unit. No water, sewer, or power requirements may be applied to single-family dwellings containing a junior accessory dwelling unit unless they apply uniformly to all single-family dwellings in the zone regardless of whether or not they contain a junior accessory dwelling unit.

Junior accessory dwelling units are exempt from any requirement to pay connection or capacity fees or charges.

Accessory dwelling units may be separately metered and shall Junior accessory dwelling units are exempt from any requirement to install a new or separate utility connection and to pay any associated connection or capacity fees or charges.

Water Availability Standards. If the lot is located within the Groundwater Sustainability Plan (GSP) area and/or is located within a designated Groundwater Deficient Area, then the proposal must comply with the objective requirements of the Water Availability Analysis Guidance Document (WAA).

No conflict with state law. If any provision of this section conflicts with Government Code Section 66310 et seq. or other applicable state law, state law shall supersede the provisions of this section.

(Ord. 1268 § 6, 2005: Ord. 1233 § 10, 2004: Ord. 980 § 1, 1991: Ord. 945 § 4, 1990: Ord. 916 § 5, 1989; Ord. 900 § 5, 1988; Ord. 867 § 14, 1988: Ord. 810 § 1, 1985; Ord. 800 § 1, 1985; Ord. 784 § 3, 1984: Ord. 766 § 2, 1984: prior code § 12412)

(Ord. No. 1323, § 22, 6-23-2009; Ord. No. 1370, § 37, 3-20-2012; Ord. No. 1379, § 160, 1-29-2013; Ord. No. 1423, § 5, 9-26-2017; Ord. No. 1456, § 5, 2-11-2020; Ord. No. 1495, § 40, 9-24-2024)