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New planning tool arrives as California prepares for more accessory dwelling units

A private planning firm in California is launching a new tool to help local governments there prepare for a pending law designed to spur more construction of accessory dwelling units (ADUs).

The Berkeley-based Community Planning Collaborative (CPC), a self-described “housing policy and ADU resource leader,” will start rolling out its ADU Plans Gallery this month. CPC said in a news release that more than 40 jurisdictions in the northern and central parts of the state have signed up to launch their own galleries. Other governmental bodies can sign up for informational sessions through CPC on June 13 and 19.

The ADU Plans Gallery ”empowers local governments to meet state laws and local housing goals while assisting residents in finding ADU plans, connecting with designers, and saving time and money on their projects,” the firm explained.

All California municipalities are mandated by state law to have a preapproval process for ADU plans by Jan. 1, 2025. Applicants who wish to build an ADU must be able to submit these plans to a local government and have them reviewed, typically by a professional architect.

”ADUs create new housing opportunities in existing neighborhoods, expanding the housing supply while building homeowner equity,” David Driskell, principal at CPC, said in a statement. ”Local governments are uniquely positioned to help residents through the daunting process of building an ADU. Digital tools like the ADU Plans Gallery reduce the time and cost of building ADUs and accelerate housing construction.”

The ADU Plans Gallery is the newest offering from CPC through, which offers services for local governments in the ADU development process.

These tools aim to help governments meet the requirements of state law in several ways. They offer a way to manage and display preapproved ADU plans, sort through dozens of prefabricated and site-built plans to add to galleries, connect ADU designers to homeowners and more.

With one of the nation’s most expensive housing markets — and one of the lowest homeownership rates among all states — California is seeking ways to increase supply.

ADUs have become increasingly popular there and in other West Coast states. Permit applications for new units in California grew from less than 10,000 in 2017 to an estimated 30,000 in 2022. And roughly 22,800 ADUs were reportedly built in 2023, accounting for one in five new homes created statewide.

In February, lawmakers in Marin County — north of San Francisco approved reduced fees to build ADUs in unincorporated areas of the county. The county justified the policy by saying that ADUs “can generate new rental income, help someone age in place, help a financially strapped college student or recently discharged military veteran, or just provide a community benefit of a new home for anyone in need.“

Last month, a Las Vegas-based housing technology startup received approval to sell factory-built ADUs in California. The prefabricated units, which span 361 square feet, are designed to reduce construction costs and minimize environmental impacts.

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