Sec. 49.04. - Accessory dwelling units—Application and processing requirements.

(a)

Step One—Submittal. The application for an accessory dwelling unit permit shall be submitted to the department concurrent with an application for a building permit. In addition to the standard submittal requirements for a building permit, an application for an accessory dwelling unit permit shall include all of the following (except as noted below):

a.

Plot plan. A plot plan, drawn to scale, showing the dimensions of the perimeter of the parcel proposed for the accessory dwelling unit; the location and dimensioned setbacks of all existing and proposed structures on the site and structures located within fifty feet of the site; all easements, building envelopes, and special requirements of the subdivision as shown on the final map and improvement plans, if any; and average slope calculations for the site.

b.

Floor plan. A floor plan, drawn to scale, showing the dimensions of each room, and the resulting floor area. The use of each room shall be identified, and the size and location of all windows and doors shall be clearly shown.

c.

Elevations. Architectural elevations of each side of the proposed structure showing all wall height dimensions, openings, exterior finishes (including siding and window materials), original and finish grades, paint color, and roof pitch. The color of the existing or proposed primary residence shall be included if necessary to demonstrate compliance with section 49.09.a, below. Applications for accessory dwelling units which do not modify a building's exterior are not required to submit elevations per this subsection c.

(b)

Step Two—Decision. The department shall approve or deny an application for an accessory dwelling unit permit within sixty days of submittal of a complete application. The accessory dwelling unit permit shall be issued only if the proposed accessory dwelling unit complies with all applicable standards in this section.

(Ord. No. 568, 5-20-2025)

Sec. 49.05. - Utility connections and fees.

(a)

Except as provided in subsection 49.04.b, a separate new utility connection and payment of a connection fee or capacity charge pursuant to state law and city fee schedule will be required for any new accessory

dwelling unit.

(b)

No new or separate utility connection or related connection fee or capacity charge will be required for accessory dwelling units that are internal conversions of existing space within a single-family residence or an accessory structure, or for accessory dwelling units that are seven hundred fifty square feet or smaller. Any fee charged for an accessory dwelling unit of seven hundred fifty square feet or more shall be charged proportionately in relation to square footage of the primary dwelling unit.

(Ord. No. 568, 5-20-2025)

Sec. 49.06. - Accessory development standards.

An accessory dwelling unit permit shall be issued only if the unit complies with the following development standards:

(a)

General.

a.

No development standards shall be applied that would prohibit up to an eight hundred square foot accessory dwelling unit that is no more than sixteen feet in height with four-foot side and four-foot rear setbacks to be constructed in compliance with all other local development standards.

(b)

Setbacks.

a.

Single-family residential districts including single-family planning department zone districts. An accessory dwelling unit shall comply with the following setback requirements:

i.

A new attached or detached eight hundred square foot accessory dwelling unit shall provide a minimum four-foot side and four-foot rear setback, and a front setback consistent with that of the primary dwelling unit in a standard zoning district. An eight hundred square foot accessory dwelling unit that complies with all other development standards may be built within the front yard setback of a lot if it is otherwise physically infeasible to build an accessory dwelling unit on other areas of the lot while maintaining the minimum rear and side yard setbacks outlined in this subsection. Side-corner setbacks shall be a minimum of four feet.

b.

Multifamily districts including multifamily districts. An accessory dwelling unit shall comply with the following setback requirements:

i.

A new attached or detached accessory dwelling unit shall provide a minimum four-foot side and four-foot rear setback. The front setback shall be consistent with a primary dwelling unit in the applicable standard zoning district, or the most similar standard zoning district. Side-corner setbacks shall be a minimum of eight feet.

c.

If the existing multifamily dwelling exceeds height requirements or has a rear or side setback of less than four feet, the department shall not require modification of the existing multifamily dwelling as a condition of approving the application to construct an accessory dwelling unit.

(c)

No setback shall be required for an existing legally constructed living area, garage, or other accessory structure that is converted to an accessory dwelling unit with independent exterior access from an existing or proposed residence. A setback of five feet from the side and rear property lines is required for an accessory dwelling unit constructed above an existing legally constructed or proposed garage.

(d)

Any new attached accessory dwelling unit, detached accessory dwelling unit or expansion of the singlefamily dwelling to support the internal conversion for an accessory dwelling shall be designed to maintain appropriate setbacks, as described in subsection B (a) and (b) above, from the future width of any abutting public streets. Future street configurations shall be based on the widths, standards and right-of-way lines in the circulation element of the City of Colusa General Plan or specifically addressed in a resolution adopted by the city council.

(Ord. No. 568, 5-20-2025)

Sec. 49.07. - Maximum floor area.

(a)

New Detached ADUs: A newly constructed detached accessory dwelling unit (ADU) shall not exceed one thousand two hundred square feet of habitable space.

(b)

New Attached ADUs: A newly constructed attached ADU shall not exceed fifty percent of the existing residential square footage, except:

• A minimum of eight hundred fifty square feet must be allowed for a studio or one-bedroom ADU.

• A minimum of one thousand square feet must be allowed for ADUs with more than one bedroom.

(c)

Internal Conversion ADUs: An ADU created entirely within an existing single-family dwelling shall not exceed forty-five percent of the existing habitable space, excluding the garage, or one thousand two hundred square feet, whichever is less. However:

○ A minimum of eight hundred fifty square feet must be allowed for a studio or one-bedroom ADU.

○ A minimum of one thousand square feet must be allowed for ADUs with more than one bedroom.

(a)

An ADU created entirely within a detached accessory structure shall not exceed one thousand two hundred square feet.

(b)

Fire Sprinkler Requirement: An automatic fire sprinkler system must be installed in any building that undergoes a substantial remodel, addition, or both, if the total floor area is increased by more than fifty percent.

(Ord. No. 568, 5-20-2025)

Sec. 49.08. - Height limit.

(a)

A one-story accessory dwelling unit shall not exceed a maximum height of 16 feet, except as follows:

a.

The department shall allow an additional two feet in height (up to eighteen feet) to accommodate a roof pitch on an accessory dwelling unit that is aligned with the roof pitch on the primary dwelling unit.

b.

A detached accessory dwelling unit on a lot with an existing or proposed single-family or multi-family dwelling unit that is within one-half mile walking distance of a major transit stop or a high-quality transit corridor shall not exceed a height of eighteen feet.

c.

A height of eighteen feet is also permitted for a detached accessory dwelling unit on a lot with an existing or proposed multifamily, multistory dwelling. A height of twenty-five feet applies to an accessory dwelling unit that is attached to a primary dwelling. This provision does not require the department to allow an accessory dwelling unit to exceed two stories.

(b)

A two-story accessory dwelling unit shall not exceed a maximum height of twenty-seven feet. No accessory dwelling unit shall exceed twenty-seven feet in height.

(c)

When an accessory dwelling unit is located above an existing or proposed garage, carport or other accessory structure, the entire combined structure shall not exceed twenty-seven feet in height. No accessory dwelling unit shall exceed twenty-seven feet in height.

(Ord. No. 568, 5-20-2025)

Sec. 49.09. - Lot coverage.

An accessory dwelling unit (ADU) must comply with the lot coverage requirements of the applicable zoning district. If the property is in a zoning district without specific ADU standards, the most similar zoning district shall apply, as determined by the planning department.

(Ord. No. 568, 5-20-2025)