40.260.020 Accessory Dwelling Units – Urban
A. Purpose.
The purpose of this section is to:
1. Provide additional smaller, subordinate dwelling units on a lot with, or in, an existing or new single-family detached dwelling.
2. Provide for a greater range of choices of housing types in residential districts that contribute to the character of the residential neighborhood.
(Amended: Ord. 2024-03-02)
B. Applicability.
1. Accessory dwelling units may be allowed in the R1-20, R1-10, R1-7.5, R1-6, R1-5 zones or on any Residential (R) or Office Residential (OR) lot developed with an existing or planned single-family detached dwelling, subject to the requirements of this section.
2. A lot of record lawfully occupied by two (2) or more single-family detached dwellings per Section 40.200.050 does not qualify for an ADU, unless the lot is short platted under Chapter 40.540. If a short plat is approved, an ADU for each dwelling unit is permitted only if all dimensional standards of the underlying zone and all other provisions of this section are met.
(Amended: Ord. 2024-03-02)
C. Development Standards.
1. Up to two (2) ADUs per legal lot are permitted and they must be accessory to a single-family detached dwelling. All of the following ADU types, in any combination, are permitted:
a. Internal conversion within an existing dwelling;
b. The addition of new square footage to the existing house or to a garage;
c. Conversion of an existing garage, including existing garages within nonconforming setbacks; provided, that the nonconformity predated April 26, 2024, and the portion of the ADU within the setback does not increase the height of the existing garage;
d. Inclusion in the development plans for, or as part of, the construction of a new single-family detached dwelling unit; or
e. A separate detached structure containing one (1) or two (2) dwelling units on the same lot as the primary dwelling unit when the structure is located behind the front building plane of the primary dwelling. However, detached accessory units may be placed forward of the front building plane on lots with a front yard setback of forty (40) feet or greater, provided the width of the front facade of the ADU does not exceed fifty percent (50%) of the width of the primary dwelling’s front facade.
f. Subject to the requirements of this section, a manufactured or modular home can be considered an ADU for the purposes of this subsection.
2. An ADU shall conform to the standards of the zone, including but not limited to lot coverage and setbacks.
3. Building height of an ADU shall meet the height requirements of the zone.
4. Allowable Size.
a. The total gross floor area of an ADU shall not exceed one thousand (1,000) square feet. Notwithstanding the definition of “gross floor area” in Section 40.100.070, “gross floor area” of an ADU means the interior habitable area including basements and attics but not including a garage or accessory structure.
b. On lots that are at least twenty thousand (20,000) square feet, the maximum square footage of an ADU may be increased up to one thousand five hundred (1,500) square feet; however, the combined maximum square footage of two ADUs shall not exceed two thousand (2,000) square feet.
c. The total floor area of a basement of the primary dwelling may be used as the ADU exceeding one thousand (1,000) square feet; provided, that there is a separate exterior entrance and the basement area does not exceed the size of the primary dwelling unit.
d. The minimum area of an ADU shall be one hundred fifty (150) square feet.
5. Parking.
No parking is required for the ADU.
6. An ADU shall connect to public sewer and water unless a sewer waiver is obtained under Section 40.370.010.
7. ADUs shall be subject to a seventy-five percent (75%) reduction in school, transportation and park impact fees from the rate imposed for multifamily dwelling units.
(Amended: Ord. 2024-03-02)
D. Design Standards for Historic Structures.
If an ADU is on the same lot as or within a historic structure which has been designated on the national, state or local historic register, the following design guidelines are applicable:
1. Exterior materials should be of the same type, size and placement as those of the primary dwelling structure.
2. Trim on edges of elements of accessory structures and additions should be the same as those of the primary structure in type, size and placement.
3. Windows in any elevation which faces a street should match those in the primary structure in proportion, i.e., same height, width and orientation (horizontal or vertical).
4. Pediments and Dormers.
Each accessory dwelling unit over twenty (20) feet in height should have either a roof pediment or dormer if one (1) or the other of these architectural features is present on the primary dwelling.
(Amended: Ord. 2024-03-02)
E. Process.
1. Accessory dwelling units are exempt from site plan review under Section 40.520.040.
2. Building permits are required to ensure compliance with applicable fire, health, and safety codes.
(Amended: Ord. 2010-08-06; Ord. 2018-01-17; Ord. 2024-03-02)