ADU Handbook #1: Understanding Accessory Dwelling Units (ADUs) and Their Importance

> ADU Handbook #1: Understanding Accessory Dwelling Units (ADUs) and Their Importance

From the California Department of Housing and Community Development:

“California’s housing production is not keeping pace with demand. In the last decade, less than half of the homes needed to keep up with the population growth were built.
Additionally, new homes are often constructed away from job-rich areas. This lack of housing that meets people’s needs is impacting affordability and causing average housing costs, particularly for renters in California, to rise significantly. As affordable housing becomes less accessible, people drive longer distances between housing they can afford and their workplace or pack themselves into smaller shared spaces, both of which reduce the quality of life and produce negative environmental impacts.

Beyond traditional construction, widening the range of housing types can increase the housing supply and help more low-income Californians thrive. Examples of some of these housing types are Accessory Dwelling Units (ADUs – also referred to as second units, in-law units, casitas, or granny flats) and Junior Accessory Dwelling Units (JADUs).

What is an ADU?
An ADU is an accessory dwelling unit with complete independent living facilities for one or more persons and has a few variations:
• Detached: The unit is separated from the primary structure.
• Attached: The unit is attached to the primary structure.
• Converted Existing Space: Space (e.g., master bedroom, attached garage, storage area, or similar use, or an accessory structure) on the lot of the primary residence that is converted into an independent living unit.
• Junior Accessory Dwelling Unit (JADU): A specific type of conversion of existing space that is contained entirely within an existing or proposed single-family residence.

ADUs tend to be significantly less expensive to build and offer benefits that address common development barriers such as affordability and environmental quality. Because ADUs must be built on lots with existing or proposed housing, they do not require paying for new land, dedicated parking or other costly infrastructure required to build a new single-family home. Because they are contained inside existing single-family homes, JADUs require relatively modest renovations and are much more affordable to complete. ADUs are often built with cost-effective one or two-story wood frames, which are also cheaper than other new homes. Additionally, prefabricated ADUs can be directly purchased and save much of the time and money that comes with new construction. ADUs can provide as much living space as apartments and condominiums and work well for couples, small families, friends, young people, and seniors.

Much of California’s housing crisis comes from job-rich, high-opportunity areas where the total housing stock is insufficient to meet demand and exclusionary practices have limited housing choice and inclusion. Professionals and students often prefer living closer to jobs and amenities rather than spending hours commuting. Parents often want better access to schools and do not necessarily require single-family homes to meet their needs. There is a shortage of affordable units, and the units that are available can be out of reach for many people. To address our
state’s needs, homeowners can construct an ADU on their lot or convert an underutilized part of their home into a JADU. This flexibility benefits both renters and homeowners who can receive extra monthly rent income.

ADUs also give homeowners the flexibility to share independent living areas with family members and others, allowing seniors to age in place as they require more care, thus helping extended families stay together while maintaining privacy. The space can be used for a variety of reasons, including adult children who can pay off debt and save up for living on their own.

New policies are making ADUs even more affordable to build, in part by limiting the development impact fees and relaxing zoning requirements. A 2019 study from the Terner Center on Housing Innovation noted that one unit of affordable housing in the Bay Area costs about $450,000. ADUs and JADUs can often be built at a fraction of that price and homeowners may use their existing lot to create additional housing, without being required to provide additional infrastructure. Often the rent generated from the ADU can pay for the entire project in a matter of years.

ADUs and JADUs are a flexible form of housing that can help Californians more easily access job-rich, highopportunity areas. By design, ADUs are more affordable and can provide additional income to homeowners. Local governments can encourage the development of ADUs and improve access to jobs, education, and services for many Californians.”

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