Addressing the Local Planning of Housing through the Jurisdictional Collaboration of 21 Elements

by Justin Shiu, Associate Planner

In addressing regional goals on issues such as the provision for housing, 21 Elements has set an excellent example of coordination among jurisdictions at the local level to support local planning for housing and respond to broader issues and State requirements. 21 Elements is a collaboration between the

  • County of San Mateo
  • All 20 cities in San Mateo County
  • Co-sponsored and coordinated by the San Mateo County Department of Housing (DOH)
  • City/County Association of Governments of San Mateo County (C/CAG).  

This collaboration allows for a shared funding approach to be developed between the jurisdictions, DOH, and C/CAG. 21 Elements has served as an important resource for jurisdictions responding to housing issues affecting many different communities and requirements at the State level, including Housing Elements.

As a collective resource among the participating jurisdictions, 21 Elements allows jurisdictions who are working towards a common objective to contribute towards a mutually beneficial information source for all participating parties. The ability to share research, successful strategies, and best practices help inform and guide jurisdictions through the process of developing approaches and policies. While providing a comprehensive structure for sharing and discussion, the process still allows choices to be tailored to fit each jurisdiction’s needs.

  In the preparation of Housing Elements, 21 Elements served as an important resource in obtaining State-certification while creating a locally-relevant document. 21 Elements provided relevant resources needed for the Housing Elements, including data tables for each jurisdiction, templates, and guiding documents. Participating members were also given the opportunity to work with the 21 Elements team in the preparation of the Housing Element document for their individual jurisdictions. All 21 jurisdictions within San Mateo County had completed State-certified Housing Elements for the RHNA 4th cycle (2007-2014) and RHNA 5th cycle (2015-2023).

As a central hub of information and coordination, 21 Elements is able to pursue work on a variety of housing issues to address similar challenges shared by member jurisdictions and related to broader housing issues. In addition to Housing Element preparation, 21 Elements facilitated a countywide nexus study used by 14 participating members to establish legally-defensible development impact fees and regulations. Recently, 21 Elements has been assisting in short-term vacation rentals, tenant displacement, linkage fees, and accessory dwelling units.

Accessory dwelling units have been brought to greater attention as a result of the new State ADU law (AB2299 and SB 1069) intended to promote ADU development; 21 Elements has considered additional ways to promote ADUs within San Mateo County. 21 Elements has proposed a number of possible tasks to support ADU development through resources that would be available to participating members. Some of the considered tasks include:

  • ADU focus groups
  • A Design and Process Manual to guide owners interested in constructing ADU
  • An ADU Web Portal containing information for public access, and
  • Hosting an ADU showcase event

Although the new State ADU law establishes a statewide approach to promote ADU development, 21 Elements is laying out an approach that further promotes ADUs and is locally relevant for the jurisdictions in San Mateo County.

In bringing together the 21 jurisdictions and providing them with assistance in planning for housing, 21 Elements has helped local jurisdictions pursue policies and actions to establish opportunities for housing within their communities, which also helps tackle the broader collective housing need.

The success of the collaboration is shown in the certification of Housing Elements in the last two RHNA cycles and the continued work in assisting the implementation of the Housing Elements. After the completion of Housing Elements, the continued importance of 21 Elements is established in its ability to serve as a central information resource, be a venue to facilitate discussion, and operate as a focal point to promote communication and coordination on tackling housing issues over time. This demonstrates that local collaboration is an integral resource in responding to broader housing needs and policies.


 21 Elements 2017/2019 Work Plan. April 21, 2017