Have an Older Unpermitted ADU? What San Diego Owners Can Do

Finding out that a backyard unit or converted space may lack permits can feel unsettling, especially if you did not build it. If you want to legalize an unpermitted ADU in San Diego, start by checking where the property is and when the unit was built. Those facts determine which permitting guidance to follow.

Who may qualify for the city process?

The City of San Diego offers a streamlined path for qualifying accessory dwelling units (ADUs) and junior ADUs (JADUs) built without a building permit before January 1, 2020. An older unpermitted granny flat is not automatically eligible: the space must meet the applicable ADU or JADU definition, and its location and condition matter. The city’s Information Bulletin 242 explains the criteria and the conditions that must be corrected.

This is a City of San Diego process. A San Diego County mailing address does not establish that a home is within city limits. Unincorporated county properties follow County of San Diego guidance. If the property is in another city, check that city’s permitting guidance.

Three steps to legalize an unpermitted ADU in San Diego

1. Confirm jurisdiction and history. Identify the agency that issues permits for your address. Gather dated photos, past listings or leases, contractor receipts, utility records, and any previous permits or notices. The city asks for evidence of the unit’s construction date and a date on the plans.

2. Review the unit’s condition. Ask a licensed design professional or general contractor to assess the space against the city’s checklist. Look at exits, alarms, plumbing, electrical work, heating, and structural condition. The bulletin describes an option for a confidential third-party inspection before applying.

3. Read the application and inspection instructions. For a qualifying city property, review Bulletin 242’s required site plan, floor plan, and completed checklist. The city requires online submission of a Building Permit application and conducts inspections after permit issuance. Ask the city which documents and corrections apply to your unit before planning construction.

Why professional review matters

An existing unit may need design changes, safety upgrades, or construction work to address substandard conditions. A professional can help distinguish the original work from later alterations: the city says new work and installations completed after January 1, 2020 are subject to current applicable codes. Some site conditions may take a project outside the streamlined process or require more documentation. Reviewing these issues early helps you define a realistic scope of work.

If you are sorting through an older unit’s history and condition, contact MDD Homes to discuss the property and what you are hoping to do.

FAQs

Does an old unit become legal automatically? No. A qualifying unit still needs a permit application, any necessary corrections, and inspections to complete the permit.

What if my property is outside the City of San Diego? Check with the agency that permits your address. The county has separate ADU guidance for unincorporated areas. If your property is in another city, check that city’s guidance.