Attached accessory dwelling units shall not exceed 25 feet in height except when the accessory dwelling unit is the result of the conversion of existing space or accessory dwelling units are proposed as part of a new planned unit development. Except for an attached statewide Exemption Accessory Dwelling Unit standard as defined in Section 18.106.020E.1, attached accessory dwelling units shall be subject to the minimum front, rear, and side yard requirements of the main structure as identified in Chapter 18.84, including requirements prescribed in Section 18.84.100. No setbacks are required for a legally existing living area that is converted to an accessory dwelling unit or to a portion of an accessory dwelling unit.
Height of the attached accessory dwelling unit is measured vertically from the average elevation of the natural grade or finished grade, whichever is lower, of the ground covered by the accessory dwelling unit to the highest point of the structure including parapet or to the coping of a flat roof, to the deck line of a mansard roof, or to the mean height between eaves and ridges for a hip, gable, or gambrel roof. Accessory dwelling units are limited to two stories. An accessory dwelling unit proposed on the second story shall not exceed 25 feet in height and shall meet the objective standards for second-story accessory dwelling units identified in Section 18.106.060.C.2.
The gross floor area of an attached accessory dwelling unit shall not exceed 50% of the gross floor area of the existing main dwelling unit or 800 square feet, whichever is greater, with a maximum increase in floor area of 850 square feet if the accessory dwelling unit is a studio or one-bedroom unit or 1,000 square feet if the accessory dwelling unit is two or more bedrooms. Accessory dwelling units that result from conversion of existing space may exceed these size limits. The gross floor area of the existing main dwelling unit is to be calculated based on the size of the unit prior to the accessory dwelling unit/conversion. In no case shall this requirement necessitate an accessory dwelling unit to be less than: (1)a 150 square foot efficiency unit; (2) 850 square feet if the accessory dwelling unit is a studio or one-bedroom unit; or (3) 1,000 square feet if the accessory dwelling unit is two or more bedrooms.