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Second Units
Last Updated 5/6/2010

Government Code Section 65583.1(a) allows a city or county to identify sites for second units based on the number of second units developed in the prior housing element planning period whether or not the units are permitted by right, the need for these units in the community, the resources or incentives available for their development, and any other relevant factors, as determined by the department. Nothing in this section reduces the responsibility of a city or county to identify, by income category, the total number of sites for residential development as required.

Requisite Analysis

Local governments can employ a variety of development strategies and/or commit to specific program actions to address the adequate sites requirement. As provided in Government Code Section 65583(c)(1)). In addition to identifying vacant or underutilized land resources, local governments can address a portion of their adequate sites requirement through the provision of second units.

To rely on second units as part of an overall adequate sites strategy to accommodate (a portion) of the regional housing need, the element must include an estimate of the potential number of second units to be developed in the planning period based on an analysis that considers the following factors:

  1. the number of second units developed in the prior planning period;
  2. community need for these types of housing units,
  3. the resources and/or incentives available that will encourage the development of second-units; and
  4. other relevant factors as determined by HCD.

The projection of second-unit development must be based on realistic capacity and development trends of second units in the previous planning period. In addition, the housing element must describe and analyze factors that could affect second unit development within the planning period. At a minimum, the element should analyze development standards (i.e., heights, setbacks, minimum unit sizes, lot coverage, parking standards, etc.), what zones allow second units (by right), architectural review standards, fees and exactions, and any other components of the ordinance potentially impacting or constraining the development of second units.

Second-Unit Affordability: The housing element should also include an analysis of the anticipated affordability of second units. The purpose of this analysis is to determine the housing need by income group that could be accommodated through second-unit development. Second-unit affordability can be determined in a number of ways. As an example, a community could survey existing second units for their rents and include other factors such as square footage, number of bedrooms, amenities, age of the structure and general location. Another method could examine market rates for reasonably comparable rental properties to determine an average price per square foot in the community. This price can be applied to anticipated sizes for second units to estimate the anticipated affordability of second units.

Frequently Asked Questions About Second Units

City of Santa Cruz

Accessory Dwelling Unit (ADU) Development Program
The City of Santa Cruz’s ADU Development Program provides opportunities for additional affordable rental housing, while providing homeowners a chance to supplement mortgage payments. The Program has received recognition nationwide and is the recipient of awards including League of California Cities 2004 Helen Putnam Award for Excellence and the Environmental Protection Agency 2004 National Award for Smart Growth Achievement – Policies and Regulations. The program works implement the development of well-designed ADUs while helping to minimize the impact of population growth on the community by providing more rental housing in the developed core and promoting infill development and sustainable land-use patterns. Through the ADU Development Program, the City of Santa Cruz offers technical and financial assistance including an ADU manual detailing the development process, relevant zoning, design standards, building codes and showcases of ADU Prototype designs.

See LINKS below for additional information and FAQs on state planning law related to second units, a second-unit bibliography prepared by HCD, and other program resources including examples of local program actions.

Sample Analyses