Collins Family Trust, et al., Design Review (P4641) and Accessory Dwelling Unit Permit (P4642)

The applicant requests Design Review approval to increase the roof height of a combined 153-square-foot portion of an existing primary residential structure that does not conform to the minimum required setbacks, and to construct a multistory 675-square-foot addition that would exceed the maximum floor area ratio, on a developed lot in the unincorporated community of Greenbrae. Additionally, the applicant requests approval for an Accessory Dwelling Unit Permit to construct a new 1,000-square-foot attached Category Two Accessory Dwelling Unit (ADU). The 828 square feet of proposed development would result in a floor area ratio of 34 percent on the 5,926-square-foot lot.

The proposed increase in roof height to those portions of the existing primary residential structure that do not conform to the minimum required setbacks will occur on the northern and southern exterior elevations, with an increase of no more than three feet above the existing roofline on either elevation.

The area of the existing roof to be raised on the northern exterior elevation would measure 89 square feet, reach a maximum height of 10 feet above grade, and not increase the floor area ratio. It would also maintain the following setbacks: 24 feet, 5 inches from the eastern front property line; 5 feet, 8 inches from the northern side property line; 38 feet, 2 inches from the southern side property line; and 34 feet, 11 inches from the western rear property line.

The area of the existing roof to be raised on the southern exterior elevation will measure 64 square feet, reach a maximum height of 11 feet, 6 inches above grade, and not increase to the floor area ratio. It would maintain the following setbacks: 26 feet, 9 inches from the eastern front property line; 55 feet from the northern side property line; 6 feet from the southern side property line; and 49 feet, 4 inches from the western rear property line.

The proposed 675-square-foot multistory addition would be partially constructed within the legal footprint of the primary residential structure, which does not conform to the minimum required setbacks, and would exceed the maximum floor area ratio by no more than 261 square feet. It would reach a maximum height of 29 feet, 6 inches above grade and maintain the following setbacks: 38 feet from the eastern front property line; 6 feet, 8 inches from the northern side property line; 29 feet, 5 inches from the southern side property line; and 24 feet, 4 inches from the western rear property line.

The proposed 1,000-square-foot attached Category Two ADU would have a maximum height of 28 feet, 1 inch above grade and would maintain the following minimum setbacks: 26 feet, 3 inches from the eastern front property line; 11 feet, 11 inches from the northern side property line; 10 feet, 1 inch from the southern side property line; and 25 feet, 6 inches from the western rear property line.

Various site improvements would also be entailed in the proposed development, such as the structural modification or removal of approximately 112 linear feet (58 percent) of the existing exterior walls of the primary residential structure, the installation of architectural features including decks and screening walls, landscaping with a variety of trees, shrubs, and other vegetation, and hardscaping consisting of previous and impervious surfaces such as pathways and a driveway.

Design Review approval is required pursuant to Section 22.54.045(E) of the Marin County Development Code because the project proposes to increase the roof height of portions of an existing primary residential structure that encroach on the required setbacks by no more than three feet above the existing roof height.

Design Review approval is required pursuant to Section 22.54.045(B) of the Marin County Development Code because the project proposes to increase the floor area ratio by no more than 35 percent or 300 square feet, whichever is more restrictive, within the footprint of a legal or legal non-conforming building.

Accessory Dwelling Unit Permit approval is required pursuant to Section 22.32.120(B) of the Marin County Development Code because the project proposes to construct a new Category Two ADU.