Guide to Accessory Dwelling Units (ADUs) on Single-Family Lots

This guide outlines the development standards, design requirements, and regulations for establishing Accessory Dwelling Units (ADUs) on lots zoned for single-family residential use.

Eligibility and Number of Units

An ADU is permitted on any lot within the city that contains a legal, existing, or proposed single-family residence [§ 17.72.026.A].

• Standard Allowance: A maximum of one (1) attached or detached ADU is permitted per lot with a proposed or existing single-family residence [§ 17.72.026.B.1].
• Bonus Allowance: A lot with a single-family residence may have both one (1) Junior Accessory Dwelling Unit (JADU) and one (1) detached ADU [§ 17.72.026.B.1.a].
• Floor Area Ratio (FAR): Lots within the R1 and/or RR zoning designations may be developed with an ADU and JADU so long as the total building floor area on the lot does not exceed a Floor Area Ratio (FAR) of 0.5 [§ 17.82.030.A.4].

Size and Height Limitations

Maximum Floor Area

The maximum floor area for a standard ADU is determined by the number of bedrooms [§ 17.72.024]:

• Studio or One-Bedroom: Maximum 850 square feet.
• Two or More Bedrooms: Maximum 1,000 square feet.

Note: Detached ADUs permitted under the special exemption provisions of § 17.72.027 are limited to a maximum of 800 square feet.

Height Limits

• Standard Height: ADUs shall not exceed 16 feet in height [§ 17.72.026.I.2].
• Over a Garage: If constructed over a permitted garage or carport, the ADU may reach the height of the primary residence or up to 35 feet (25 feet if multi-family, but 35 feet generally for primary residence matching) [§ 17.72.026.I.2, § 17.72.026.B.2.b].

Setbacks and Location

• Conversions: No setbacks are required for ADUs created by converting existing living areas or accessory structures, or for new ADUs constructed in the exact same location and dimensions as an existing structure [§ 17.72.026.O.1].
• New Construction: All other ADUs must have a minimum setback of four (4) feet from side and rear lot lines and must comply with all applicable front yard setbacks [§ 17.72.026.O.2].
• Window/Door Restrictions: Any ADU utilizing reduced setbacks cannot have doors or windows within that setback area unless required for health and safety [§ 17.72.026.M].
• Passageways: No passageway is required in conjunction with the construction of an ADU [§ 17.72.026.K].
• Attached Garages: A detached ADU may include an attached, unconditioned garage not exceeding 250 square feet [§ 17.72.026.P].

Parking Requirements

The city requires a maximum of one (1) additional parking space per ADU or per bedroom, whichever is less. This space may be provided as tandem parking on an existing driveway or within a setback area (unless deemed infeasible for safety/topographical reasons) [§ 17.72.026.E.1].

Parking Exemptions: No parking spaces are required for an ADU in any of the following scenarios [§ 17.72.026.E.2-4]:

• It is a studio unit without a separate bedroom.
• It is located within one-half mile walking distance of public transit.
• It is located within an architecturally and historically significant district.
• It is part of a proposed or existing primary residence or an accessory structure.
• On-street parking permits are required but not offered to the ADU occupant.
• A car-share vehicle is located within one block of the ADU.
• A garage, carport, or covered parking structure is demolished or converted in conjunction with the ADU construction (replacement parking is not required).

Design and Accessibility Standards

• Architectural Compatibility: Materials, colors, and architecture must be similar to and compatible with the primary unit [§ 17.72.026.I.1].
• Entrances: ADU entrances must face the street. If topographic or site constraints prevent this, the entrance must be screened from neighboring properties [§ 17.72.026.I.3, § 17.82.030.A.1].
• Lighting: Exterior lighting must not spill onto neighboring lots [§ 17.72.026.I.4].
• Garage Conversions: If a garage is converted, the garage door must either remain in place and look functional, or be removed. If removed, architectural features (siding, windows, trim) and landscaping must be added so the structure no longer appears to be a garage [§ 17.72.026.L, § 17.82.030.A.5].
• Accessibility: New ground-level ADUs must be designed for disability/accessibility standards, including adequate door/hallway widths, maneuvering space in kitchens/bathrooms, and structural reinforcements for grab bars [§ 17.72.026.J].

Occupancy, Rental, and Sale Restrictions

• Owner Occupancy: Until January 1, 2025, no owner-occupancy requirement applies to newly permitted ADUs on single-family lots. After this date, unless prohibited by state law, one of the units on the property must be owner-occupied, and a deed restriction must be filed to enforce this in perpetuity [§ 17.72.026.F].
• Separate Sale Prohibited: ADUs may be rented separately but cannot be sold or conveyed separately from the primary residence [§ 17.72.026.G].
• Short-Term Rentals: ADUs cannot be operated as hosted short-term rentals if they are: detached and over 800 sq. ft., attached and over 640 sq. ft., or permitted under the special exemption provisions of § 17.72.027 [§ 17.72.026.N]. Furthermore, any ADU approved under § 17.72.027 cannot be rented for a term of less than 30 days [§ 17.72.027.B].

Utilities and Fees

• Utility Connections: All ADUs must connect to public water, electric, and sewer services. No separate connection or fee is required for ADUs created entirely within a single-family dwelling (unless built alongside a new single-family dwelling) [§ 17.72.026.D.1].
• Impact Fees:
  • ADUs 750 square feet or larger: Impact fees are charged proportionally based on the size of the ADU relative to the primary dwelling [§ 17.72.026.D.2.a].
  • ADUs 749 square feet or smaller: No impact fees shall be charged [§ 17.72.026.D.2.b].
• Affordable Housing Exception: Newly permitted ADUs are exempt from application, sewer, and water hookup fees if accompanied by a 30-year deed restriction ensuring affordable rent to low or very low-income households [§ 17.72.026.D.4].
• Fire Sprinklers: Fire sprinklers are not required in the ADU if they are not required for the primary residence [§ 17.72.026.C].