40.260.020    Accessory Dwelling Units – Urban

A.    Purpose.

    The purpose of this section is to:

1.    Provide an additional smaller, subordinate dwelling unit on a lot with, or in, an existing or new house.

2.    Provide for a greater range of choices of housing types in single-family and multifamily residential districts while protecting the character of the residential neighborhood.

(Amended: Ord. 2020-03-01)

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 multifamily-zoned (Residential (R) or Office Residential (OR)) lot developed with an existing single-family dwelling, subject to the requirements of this section.

2.    A lot of record lawfully occupied by two (2) or more single-family residences 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.

3.    An ADU shall not be located in a dwelling or on a lot where a Type II home business is operating.

(Amended: Ord. 2020-03-01)

C.    Development Standards.

1.    No more than one (1) ADU per legal lot is permitted and it must be accessory to a single-family residence.

2.    ADUs require building permits to ensure compliance with applicable fire, health, and safety codes.

3.    An ADU may be created through:

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;

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 dwelling unit on the same lot as the primary dwelling unit when the accessory unit is located at least ten (10) feet behind the most distant back or side wall or other structural element of the primary dwelling unit structure.

f.    Subject to the requirements of this section, a manufactured or modular home can be considered an ADU for the purposes of this subsection.

4.    An ADU shall conform to the standards of the zone, including but not limited to lot coverage and setbacks.

5.    Building height is limited to twenty-five (25) feet for a detached ADU. Additions to existing dwellings shall meet the height requirements of the zone.

6.    Allowable Size.

    The total gross floor area of an ADU shall not exceed eight hundred (800) square feet or forty percent (40%) of the area of the primary dwelling’s living area, whichever is less, with the following exceptions for large lots with large primary dwellings or primary dwellings with basements:

a.    On lots that are at least ten thousand (10,000) square feet, the maximum square footage of an ADU is one thousand (1,000) square feet, or forty percent (40%) of the area of the primary dwelling’s living area, whichever is less; and

b.    On lots that are at least twenty thousand (20,000) square feet, the maximum square footage of an ADU is fifteen hundred (1,500) square feet, or forty percent (40%) of the area of the primary dwelling’s living area, whichever is less.

c.    The total floor area of a basement of the primary dwelling may be used as the ADU; provided, that there is a separate exterior entrance and the basement area does not exceed the size of the primary dwelling unit.

d.    The living area of the primary dwelling unit excludes uninhabitable floor area, garage and other outbuilding square footage whether attached or detached. If the primary dwelling unit is smaller than seven hundred fifty (750) square feet, the ADU may be up to three hundred (300) square feet even though this exceeds forty percent (40%) of the primary dwelling unit’s living area. The minimum area of an ADU shall be one hundred fifty (150) square feet.

7.    Parking.

    One (1) parking space shall be provided for the ADU. Parking may be provided by the following methods:

a.    On site;

b.    On-street parking; provided, that the parking space is legally available and along the ADU lot’s street frontage. Posted-time or day-restricted parking spaces do not qualify as legally available for the purposes of this section; or

c.    If no parking space is available on site or on-street, a joint agreement for off-site parking may be used subject to Section 40.340.010(A)(5).

8.    An ADU shall connect to public sewer and water unless a sewer waiver is obtained under Section 40.370.010.

9.    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. 2005-04-12; Ord. 2020-03-01)

D.    Design Standards.

1.    The exterior appearance of an addition or detached ADU shall be architecturally compatible with the primary residence. Compatibility includes coordination of architectural style, exterior building materials and colors, roof form and pitch, window style and placement, other architectural features and landscaping. The responsible official may approve variations as necessary to accommodate proposed energy efficient building features into the ADU.

2.    New entrances for an ADU created by internal conversion or by an addition to an existing primary dwelling shall be located on the side or rear of the primary residence unless it can be demonstrated that no feasible alternative exists.

3.    Exterior Finish Materials.

    Plain concrete, concrete block, corrugated metal or plywood is prohibited if they are not the predominant exterior finish material on the primary dwelling, unless these materials duplicate or reflect the predominant finish.

4.    Roof Slopes.

    For buildings over fifteen (15) feet in height, the slope of the accessory dwelling unit roof must be the same as that of the predominant slope of the primary dwelling structure.

5.    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:

a.    Exterior materials should be of the same type, size and placement as those of the primary dwelling structure.

b.    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.

c.    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).

d.    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.

6.    Accessibility.

    To encourage the development of ADA-accessible housing units, the responsible official may allow reasonable deviation from the requirements of this section for features that facilitate accessibility.

E.    Process.

    Accessory dwelling units created under Section 40.260.020(C)(3)(e) require Type I site plan review under Section 40.510.010. Building permits may be submitted at the same time as the site plan review.

(Amended: Ord. 2010-08-06; Ord. 2018-01-17)