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All ADUs, both new construction and conversion, must conform with the following requirements:

(1) Number of ADUs Per Parcel. A maximum of one attached or one detached ADU is permitted on residential parcels with legally permitted and conforming single-family dwellings; provided, that all the requirements of the PMC and applicable development regulations are met.

(2) Density. ADUs are exempt from the residential density standards of this code, due to their small size and low occupancy.

(3) Occupancy and Use.

(a) Occupancy of ADUs shall be reserved for residential uses only.

(b) Occupancy of ADUs shall be used for long-term residential purposes and may not be used for transient occupancy or short-term/vacation rental purposes. Persons residing in ADUs shall live in such residences for longer than 180 days each calendar year.

(c) Use of ADUs for uses outside of the permitted uses of this code shall be reported and enforced by the Pasco Code Enforcement Hearings Board.

(d) ADU permits shall not be permitted for any single-family residences or lots which are in violation of any applicable section of this code, including nonconforming structures or uses. The City retains discretion to require an inspection of the primary residence by a state licensed building inspector in conjunction with an ADU permit application if it has reason to believe code violations exist.

(4) Parking. Off-street parking is not required.

(5) Design. The design of the ADUs shall be complementary to the design of the principal dwelling or applicable residential design standards of PMC 25.165.100 by use of the compatible exterior wall materials, window types, door and window trims, roofing materials and roof pitch.

(a) Placement.

(i) Attached ADUs shall present the overall appearance of the structure as an individual single-family residence.

(ii) Detached ADUs shall be located to present a less dominant focus than the principal dwelling and shall be in a manner that clearly indicates it is an accessory structure to the principal dwelling.

(b) Unit Size. The size of the ADUs shall not exceed 1,000 square feet or 55 percent of the total square footage of the primary residence or dwelling, whichever is less.

(c) Unit Height. The maximum height of the ADU shall be no taller than that of the principal dwelling or 25 feet, whichever is less.

(d) Setbacks for New Construction Detached ADUs.

(i) The side and rear yard setbacks of the underlying residential zoning district shall apply.

(ii) The minimum distance between habitable structures (principal dwelling and accessory dwelling) shall be 10 feet.

(iii) The minimum distance between a habitable structure and nonhabitable structure (sheds, garages, etc.) shall be six feet.

(e) Rear Yard Coverage. A detached ADU shall occupy no more than 60 percent of the rear yard as defined in PMC 25.175.020.

(f) Location of Entrances.

(i) The location of entrances for detached ADU may be oriented towards the primary dwelling but shall not be oriented to face an existing, neighboring property.

(ii) The main entrance for detached accessory dwelling units shall be located no closer than 15 feet from the side yard property line.

(g) Exterior Finish. Exterior finish materials must visually complement in type, size, and placement the exterior finish materials of the primary dwelling.

(h) Roof Pitch. The roof pitch of the accessory dwelling must be the same as the predominant roof pitch of the primary dwelling.

(i) Windows.

(i) If the street-facing facade of the ADU is visible from the street, its windows must match, in proportion and orientation, the windows of the primary dwelling.

(ii) Second-story windows within 10 feet of the property line shall be constructed to reduce direct views into the neighboring property. Methods to do so include clerestory windows and semi-translucent glass and shall be included on the application and approved by the Department of Community and Economic Development.

(j) Access and Walkways.

(i) A separate walkway must be provided for all detached accessory dwelling units.

(ii) Walkways must be a minimum of three feet wide and made of an approved material.

(iii) Walkway materials must be distinct from any adjacent vehicle areas and may function as a shared drive/walk space along an exterior edge of a driving surface.

(k) Addressing. Accessory dwelling units must have approved clear addressing visible from the street. If the accessory dwelling is not visible from the street, an approved address, directional notation shall be uniform in location, size, height and wording complying with the fire, building and municipal code and must differentiate the primary dwelling from the ADU and must be visible from the main access point to the property.

(6) Additional Building and Utility Standards. The following set of standards are applicable to all new and unpermitted constructed detached ADUs. Any regulation not listed shall default to the provisions of the applicable building requirements of the Pasco Municipal Code.

(a) Construction Requirements. ADUs must comply with the City of Pasco’s building code (PMC Title 16) and all other refenced standards.

(b) Fire Separation Design. The location of all ADUs must comply with the required separated distances of the City of Pasco’s building code (PMC Title 16) and all referenced standards.

(c) Fire Sprinkler. A fire sprinkler system shall be required for any ADU that exceeds the maximum allowed distance to a fire hydrant.

(d) Additional Standards for Attached ADUs.

(i) Attached ADUs shall be constructed with a fire separation in accordance with the City of Pasco’s building code (PMC Title 16) and all referenced standards.

(ii) Applicants may consider the following alternatives from the above if documentation meets all three criteria below per Washington State Amendments to the IRC:

(A) The ADU is constructed within an existing dwelling unit. This requires the unit to have an approved doorway between each area or stairway allowing interior access from the primary dwelling to the accessory dwelling to have a connection with enclosed spaces and provide the appearance as one common dwelling.

(B) Either the accessory dwelling unit or primary dwelling unit is owner-occupied. This will require recording on title of an owner occupancy agreement to assure proper use now and with potential future ownership.

(C) All required smoke alarms in the accessory dwelling unit and the primary dwelling unit are interconnected in such a manner that the actuation of one alarm will activate all alarms in both the primary dwelling unit and the accessory dwelling unit.

(iii) If an existing ADU is modified to not be owner occupied, then permits are required to modify and/or verify construction meets the standards referenced above.

(e) Utilities.

(i) Utility lines and impervious surfaces must be identified on required site planning documents.

(ii) Site development considers all accessory dwellings to be accessory structures and right-of-way improvements are only necessary to address impacts created by the development. Requirements may include restoration for new or upgraded utilities, including modifications to driveway or curb access. Future conversion or change of uses will require frontage improvements as applicable through PMC 12.36.050.

(iii) Sanitary sewer and surface water services shall be built and permitted as required in the City of Pasco standard specifications.

(f) Legalization of Nonconforming Accessory Dwellings.

(i) ADUs existing prior to the enactment of these requirements, which were not lawfully established at the time of construction, may be found to be legal if the property owner applies for an ADU building permit and brings the unit up to the minimum building requirements of PMC Title 16 and this chapter. Owners of such ADUs shall be subject to the enforcement provisions as administered through the Pasco Code Enforcement Hearings Board. It shall be prima facie evidence of a violation of this chapter if the City establishes, by a preponderance of the evidence, that the existing ADU is unpermitted. This may be rebutted by evidence establishing that a permit was not required at the time of construction.

(ii) ADUs lawfully established prior to the enactment of these requirements shall be considered a lawful nonconforming structure subject to Chapter 25.170 PMC.

(g) Subdivision of Property.

(i) A detached ADU may remain on a lot or parcel where no main building exists when in event the main structure on a lot is damaged or for other reason, is required to be removed.

(ii) If a property with an existing single-family dwelling and an ADU is subdivided with a result that the ADU is on a separate property, then the ADU must either be converted to a single-family dwelling which complies with all requirements for single-family dwellings, and which may include frontage improvements for the change of use, or permits for construction of a new single-family dwelling must be submitted on the site where the ADU exists. [Ord. 4575 § 12, 2022.]