The city of Santa Cruz, Calif., in an effort to promote infill development and accommodate population growth without sprawl, has a plan to promote small housing units, or alternative dwelling units (ADUs), on lots with existing homes.

ADUs, or alternative dwelling units, “provide an excellent opportunity to increase the amount of affordable rental housing in the community while providing homeowners with a chance to supplement mortgage payments, thus making their own housing more affordable,” according to a city description of the program. Santa Cruz is one of the least affordable communities for residents to own homes.

View slideshow of the ADU prototypes.

ADUs are sometimes referred to as “granny units,” “garage conversions,” “garage apartments,” or “mother-in-law” units. ADUs can be built in garages, above garages, in basements, or as a new, standalone unit that is either attached or detached from the main home. Alleys are popular sites for ADUs.

The city’s ADU ordinance provides that ADUs can be built on residential lots of 5,000 square feet or more, and must meet setback, height and parking requirements. The city’s ordinance provides for streamlined permitting of ADUs in some cases and offers incentives for the development of these units. The city manual suggests that the total construction cost of an ADU might be in the neighborhood of $76,000.

Santa Cruz ADUs can be a maximum 500 square feet on lots ranging in size from 5,000 square feet to 7,500 square feet. For lots ranging from 7,500 square feet to 10,000 square feet, ADUs can be up to 640 square feet. And for lots in excess of 10,000 square feet, an ADU can be up to 800 square feet.

As a part of its effort to encourage ADU development, the city worked with seven architects to prepare prototype designs for a 500-square-foot ADU. Architects from San Francisco to North Hollywood submitted prototype designs.


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