San Diego ADU FAQ
These answers cover the City of San Diego unless we say otherwise. Rules change, so confirm with the City or your contractor before you build.
How big can an ADU be in San Diego?
In the City of San Diego, a new attached or detached ADU can be 150 to 1,200 square feet [1]. Converting an existing structure is not held to the 1,200 square foot limit [1]. A JADU, which sits inside the main home, can be 150 to 500 square feet [2].
Do I need a parking space for my ADU?
Usually not. The City requires no parking for ADUs outside the Coastal Overlay Zone, and none for JADUs [1]. Some exceptions apply, such as certain garage conversions in the Beach Impact area and Bonus ADUs outside a Transit Priority Area [2].
Do I have to live on the property?
Not for an ADU. The City says the owner is not required to live on site [1]. For a JADU, state law now requires the owner to live there only if the JADU shares sanitation facilities with the main home [3].
Can I rent my ADU on Airbnb?
Not as a short-term rental in the City of San Diego. An ADU may not be rented for less than 31 days in a row, and a JADU must be rented for more than 30 days [1]. Long-term rentals are allowed.
Can I sell my ADU separately?
In many cases, yes. The City says most new or existing ADUs may now be sold separately from the main home as condominiums [4]. The ADU must pass its final inspection before the condo plan is recorded, and other steps apply [2].
Do I need a permit?
Yes. The City says a building permit is required to create an ADU or JADU, with no exemptions [1]. Properties in the Coastal Overlay Zone generally also need a Coastal Development Permit, with some exceptions [1].
How long does it take?
It depends on the design and the site. Plans that use a preapproved design get a 30-day City review [1]. One San Diego builder reports that detached ADUs often take 12 to 24 months from first idea to finished unit [5].
Is the CalHFA ADU grant open?
No. CalHFA's page says the latest round of ADU grant funding was fully allocated as of December 28, 2023, and no new round is listed [6]. CalHFA also warns that anyone offering to help you get an ADU grant is running a scam [6].
What does an ADU cost?
We did not find a local survey of installed prices. National guides list $100 to $300 per square foot (2023) [7], and newer reports put many prefab units at $200,000 to $300,000 installed [8]. See our ADU cost guide.
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Sources
- City of San Diego Development Services, "Information Bulletin 400: Accessory Dwelling Unit/Junior Accessory Dwelling Unit," January 2026. Fetched 2026-11-11. https://www.sandiego.gov/development-services/forms-publications/information-bulletins/400
- City of San Diego Development Services, "Accessory Dwelling Unit/Junior Accessory Dwelling Unit," no date shown. Fetched 2026-11-11. https://www.sandiego.gov/development-services/news-programs/programs/companion-junior-units
- City of San Diego Development Services, "Regulatory Updates," no date shown. Fetched 2026-11-11. https://www.sandiego.gov/development-services/regulatory-updates
- City of San Diego Development Services, "Public Notice: Information Bulletin 400 Updates," August 27, 2025. Fetched 2026-11-11. https://www.sandiego.gov/sites/default/files/2025-08/dsd_ib400_adu.pdf
- SnapADU, "The State of Detached ADUs in San Diego (2026)," no date shown. Fetched 2026-11-11. https://snapadu.com/lessons-from-100-adu-builds-detached-adu-report-san-diego/
- CalHFA, "ADU Grant Program," status notice dated December 28, 2023. Fetched 2026-11-11. https://www.calhfa.ca.gov/adu/
- HomeGuide, "How Much Does It Cost to Build an ADU?," November 13, 2023. Fetched 2026-11-11. https://homeguide.com/costs/adu-cost
- Block Renovation, "Prefab ADUs: What is the True Cost Savings," February 4, 2026 (updated June 17, 2026). Fetched 2026-11-11. https://www.blockrenovation.com/guides/prefab-adus-what-is-the-true-cost-savings