San Diego County is one step closer to joining other California communities in letting ADUs be sold as condos. The latest move to loosen rules governing accessory dwelling units in the county’s unincorporated areas got a warm reception Friday from county planning commissioners, who voted unanimous ly to let property owners sell detached ADUs under a new state law. The law, Assembly Bill 1033, allows jurisdictions to opt into permitting such sales. Cities like San Diego, San Jose and Santa Cruz now allow ADU condo sales. The Board of Supervisors is expected to vote in March on whether to include the measure in an update of the county’s ADU ordinance. If they support it, San Diego County would become the second county in California, after San Francisco, to opt into an ADU sales program under the 2023 law. Only detached ADUs would be eligible for conversion into condos and eventual sale. Planning commissioners considered other alternatives to the measure. Those included letting ADUs attached to a house or multi-family building be sold, or not allowing already-built ADUs to be grandfathered in to the new rules. County staff said attached ADU sales could disrupt typical development patterns in rural towns. And they said restricting sales to new ADUs would undermine the county’s goals for expanding housing options. Planning commissioners agreed. Planning Commission Chair Ronald Ashman said ADU sales could be a good fit for areas like Spring Valley and Bostonia, which are near public transit and under the county’s land-use authority. “That flexibility, I think, could serve the public,” Ashman said. Despite the support from commissioners, fears still linger for more rural parts of the county about what more ADU construction could mean. “I am concerned about rural areas,” Ashman added. “I recognize the little bit of chaos that can be kind of created by introducing these types of structures into already established communities. It’s a general balance that would have to be achieved.” Stephen Stonehouse speaks during public comment at the San Diego County Planning Commission hearing for a proposal to allow accessory dwelling unit sales in unincorporated areas of the county, San Diego, Friday, Dec. 5, 2025. (Zoë Meyers / For The San Diego Union-Tribune) Dori Rattray, chair of the Valley Center Community Planning Group, said her town already has a strained sewer system, something she said more housing density could make worse. Like other unincorporated communities facing the risks of wildfires, Valley Center residents worry how new housing development could affect fire response, Rattray said. “If you add additional resources, not only are you pulling from water, you’re pulling from emergency response, you’re pulling from waste. So obviously those are concerns,” she said. Bonita resident Stephen Stonehouse told planning commissioners he finished building an ADU on his property in 2022, all with an eye on eventually splitting his lot and converting the ADU into a condo. “Which is what my wife and I had intended to do when we first got involved in the ADU — to use it for ourselves when we get old, and sell the main house,” Stonehouse said. In the unincorporated areas, ADUs have increasingly been a key driver in housing development. They accounted for 1,552 residential building permits in the unincorporated area from 2021 through 2024, according to county housing data. In 2020, just 159 ADUs were permitted in the unincorporated areas. Last year, 489 were permitted. Meanwhile, the development of single-family and multi-family housing has slowed over the same period. In 2021, the county permitted 960 single-family homes. Last year, it permitted little more than a third that many — just 336. Between 2021 and 2022, multi-family development jumped from 47 units to 329. But from 2023 to 2024, new multi-family permits fell from 216 to 174. ...read more read less