Planning Commission to Review Modifications to the "Accessory Dwelling Unit" Ordinance

Planning Commission Meeting
September 11, 2018
7:00 pm
Mill Valley City Hall

Accessory Dwelling Units (ADUs) are an important and well respected piece of Mill Valley’s smaller scale, affordable housing stock.  Approximately 7% of the City total housing units (6,534) are ADUs. The proposed modifications to ADU regulations (contained the Mill Valley Municipal Code section 20.90) incorporate direction received from City Council and Planning Commission to establish Junior ADU regulations and create addition regulation, where possible, to ensure that ADUs are maintained as truly separate, rentable units and used for the intended purpose of a dwelling unit. 

On July 10, 2018, Planning Commission reviewed the proposed modifications to the ADU ordinance, which are summarized below. At the meeting, Planning Commission agreed to many ideas and continued the discussion to the September 11, 2018, directing staff to revise the Ordinance based on feedback received at the June 26, 2018 meeting. The Draft Ordinance will available to download prior to the September 11, 2018 meeting, and will be announced in MV Connect when it is available. Written comments are welcome prior to the hearing. See below for contact information.

Summary of Proposed Modifications

Discretionary “Exceptions”

The Draft Ordinance establishes an "exception' review and approval process for those applicants wishing to build an ADU on their property, but do not meet the basic development standards established in the ordinance (e.g. number of ADUs on a property, maximum size or height, lot size/coverage, allowable square footage, setbacks). This process is intended to help address the interests of owners with properties that do not meet standards, while also fostering additional affordable housing built in town. 

The Draft Ordinance indicates that an “exception” (rather than a more rigorous "variance") may be granted through the design review process, if the proposed exception to the development standards do not adversely affect the health or safety of persons residing or working in the neighborhood of the property of the applicant and will not be detrimental to the public welfare or injurious to property or improvements in the neighborhood. In order to qualify to apply for an “exception,” the applicant must agree to the additional requirements described below.

Floor Area Bonus. 

Commission have discussed the current practice of granding a Floor Area bonus to ADU's, and have suggested a sliding scale for the bonus for lots between 8,000 and 15,000 square feet. Lots over 15,000 will not be eligible for the bonus under the new proposed regulation, since typically larger scale lots do not need additional square footage to build. It was also acknowledged that larger lots are typically in the hillsides, and may not be the most appropriate area for a large home with additional square footage for an ADU. See table below for details.

Additional Design Standards and Deed Restriction for ADUs with Floor Area Bonus.

Mill Valley leaders are interested in ensuring the ADUs are utilized for their intended purposes, as a dwelling unit, particularly those ADUs that are created by granting additional square footage on the property through the FAR bonus.  As a means of doing so, the following criteria is proposed for those ADUs created with the square footage bonus.
Additional Design Standards:

  • No internal connections to primary residence; 
  • A closet required for every bedroom space (defined in the draft ordinance);
  • The primary residence must comply with parking standards (2 off-street parking spaces and 1 guest space when on-street parking not available); and
  • At least 1 parking space required for the ADU.  

Additional Requirements and Deed Restrictions:

  • Require the ADU to be rented to an “Affordable Household” (Moderate, low or very low income affordability levels, as defined in the Draft Ordinance), or to an adult immediate family member (defined in the Draft Ordinance).
  • Require annual owner verification of renting the ADU space, including submittal of the rental agreement documenting the rent charged, household size, and gross household income.  
Comments and questions can be sent to Danielle Staude, Senior Planner at