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The original item was published from 10/8/2021 2:15:15 PM to 10/8/2021 2:26:16 PM.

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Planning & Building

Posted on: October 8, 2021

[ARCHIVED] Zoning Code Updates

Planning Commission to Review the Accessory Dwelling Unit Ordinance and Proposed New Ordinance to Address New State Legislation (SB9)

On October 12, 2021 Planning Commission will consider recommending that City Council adopt two resolutions to update the Accessory Dwelling Unit Ordinance and establish regulations for two-unit project that are now permitted in Single-Family zones based on new state regulations under Senate Bill 9.  The Draft ADU Ordinance that is modelled based on the City’s existing Urgency ADU Ordinance and direction received at several Planning Commission and City Council Study Sessions.  

To download material: See the the Zoning Code Updates Page

To submit comments: Please provide written comments prior to the meeting to Danielle Staude at; or provide oral comments at the meeting by attending the hearing, see details below. 

To attend the meeting: meetings are now in person.  The meeting starts at 7:00pm and is held in the Mill Valley City Hall Council Chambers located at 26 Corte Madera, 2nd Floor, Mill Valley, CA.

To watch or view the meeting remotely or access information after the meeting: Go to the watch meetings online website and select the Planning Commission tab and October 12, 2021 date. 

Addition Details about the Ordinance Updates

Proposed revisions to the Ordinance beyond the existing Urgency ADU Ordinance include the following:      

    Fire Safety: Staff continues its collaboration efforts with the Southern Marin Fire District and intends to bring forward a separate ordinance that would adPhoto 1 Zoning Update 10-2021opt local amendments to the Fire Code specifically to address ADUs in the Very High Fire Severity Zone. The local amendments will be comprised of objective standards that can be applied the ministerial ADU process.

    Rear and side setbacks: Clarification for corner and through lots since State Law allows reduced four foot “rear and side” setbacks for qualifying ADUs and two-unit projects.  

    Breezeway: Defining and clarifying that an ADU connected by breezeway is considered a “Detached ADU” and is therefore subject to height restrictions of 16 feet.  

    Overall ADU Height: Defining and clarifying that an ADU that qualifies under State law incentives may not exceed 16 feet which is defined in the Draft ADU Ordinance as “the vertical distance from the finished floor to the highest point of the Unit, which may be the ceiling....”  

    Local Floor Area Exemption: Re-establish the local Floor Area exemption for ADUs and clarify the Allowable “Adjusted Floor Area”.  At previous study sessions, Planning Commission and City Council were supportive of providing a local incentive for ADUs above/below a garage as well as reinstituting the adjustment to Allowable Floor Area based on the size of a lot.  

The Draft ADU Ordinance now reflects, what was actually in place before the Interim Ordinance, with a slight adjustment to the language to accommodate State Law. Following is relevant language in the Draft ADU Ordinance: 

The following will be subtracted from the paragraph 20.16.040(A)(1)(a) total above during the renovation or development of a Single-Family Dwelling Unit:

i.      For lots of up to 8,000 square feet of gross area, up to 500 square feet of garage floor area.
ii.     For lots ranging from 8,000 to 10,000 square feet of gross area, up to 500 square feet of garage area or up to 800 square feet of combined garage and residential second unit area.
iii.    For lots over 10,000 square feet in gross floor area, up to 500 square feet of garage area or up to 1,000 square feet of combined garage and Accessory Dwelling Unit area.

Draft Ordinance to Allow Two-Units in a Single-Family Zone include the following:

On September 16, 2021, Governor Newsom signed Senate Bill 9 (SB 9), which requires cities and counties in urbanized areas to ministerially approve up to two residential units (either contained in one structure typically known as a “Duplex” or in separate structures) and “urban lot splits” for parcels located in single family residential zones. Ministerial approval means that the City cannot conduct a public hearing or discretionary review. SB 9 will become effective on January 1, 2022.   Photo 2 Zoning Update 10-2021

The new legislation also creates allowances for urban lot splits, which will be addressed in a subsequent update to the subdivision ordinance (MVMC, Title 21).

The following provides a brief summary of key provisions for each type of ministerial approval required by SB 9 that is addressed in the new Draft Ordinance: 

    Number of Units: Up to two new housing units, or the addition of one new unit to an existing unit. The two units may be adjacent or connected. An ADU or JADU may also be added to each unit when combined not combined with an urban lot split. 

    Objective Development Standards: Objective zoning and development standards may be applied, provided the standards do not physically preclude the construction of up to two units of at least 800 square feet each.  

    Rear and Side Setbacks: Up to four feet may be required from the side and rear lot lines, provided that no setback may be applied to existing structures or structures constructed in the same location and to the same dimensions as an existing structure. The City can apply its own front setback, provided that the front setback does not preclude the development of at least two units of at least 800 square feet each.  

    Parking: One off-street parking space may be required for each unit, unless the parcel is located within one-half mile of a high-quality transit corridor or major transit stop or there is a car share vehicle located within one block of the parcel.

    Short-Term Rentals Prohibited: Local agencies must require that tenancies be longer than 30 days.

Local agencies may deny applications for two-units under the following circumstances:

o    The development is located in (1) the coastal zone; (2) wetlands; (3) very high fire severity zones, except if the proposed development incorporates fire hazard mitigation measures pursuant to existing building standards; (4) earthquake fault zones; (5) special flood hazard areas (100-year flood zones); (6) conservation or sensitive habitat areas; and (7) certain other areas designated in state housing law.

o    The development would require the demolition of (1) an affordable housing unit; (2) a rent controlled unit; (3) a unit that has been rented within the past three years; (4) housing units removed from rental market within the past 15 years under the Ellis Act; (5) more than 25 percent of the existing structure’s walls, unless permitted by the local agency or the site has not been occupied by a tenant in the last three years; or (5) a designated historic site.

o    The building official finds that the development would have a specific, adverse impact on public health and safety or the physical environment that cannot be mitigated. A “specific, adverse impact” means “a significant, quantifiable, direct, and unavoidable impact, based on objective, identified written public health or safety standards, policies, or conditions as they existed on the date the application was deemed complete.” State law specifies that a general plan or zoning inconsistency is not considered a specific, adverse impact. 

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