Converting a garage to an ADU in San Diego County

San Diego has one of the most active ADU markets in California. A combination of high rents, a chronic housing shortage, and state legislation that stripped most local barriers has made garage ADU conversions one of the most common renovation projects in the county. If you own a home with an attached or detached garage, you may be sitting on a second unit that can generate $1,500-$2,500 per month in rental income or provide housing for a family member.

This guide covers what you need to know before you start: what types of ADUs are possible, how the permitting process works in San Diego, what state law changed, and what the build process looks like from first call to certificate of occupancy.

What types of ADU can a garage become

California law recognizes three categories relevant to garage conversions.

Junior ADU (JADU): A JADU is created within the existing footprint of the primary dwelling, which under state law includes an attached garage. It must be no larger than 500 square feet, have its own entrance (which can be from a shared access point), and include an efficiency kitchen. A full bathroom is not required, but most owners add one. A JADU does not require replacing any removed parking spaces. It can be rented to any tenant but cannot be sold separately from the primary home.

Attached ADU: An attached garage that is converted into a full apartment, including a full kitchen and full bathroom, becomes an attached ADU. Unlike a JADU, there is no 500 square foot cap; the unit can use the full garage footprint. State law as of 2020 generally requires jurisdictions to allow attached ADU conversions on single-family lots with minimal restrictions.

Detached ADU: A detached garage converted to a living unit becomes a detached ADU. Detached ADUs can be expanded with a modest addition (up to 150 square feet in some cases under state law) to add features like a bathroom or entry vestibule. Height limits and setback requirements vary by jurisdiction.

What state law changed for San Diego homeowners

Before 2020, many San Diego cities and the county imposed significant restrictions on ADUs: minimum lot sizes, owner-occupancy requirements, design standards that added cost, and parking replacement requirements that made conversions nearly impossible in dense neighborhoods.

AB 68, AB 881, and subsequent state legislation eliminated most of those barriers. Key changes that directly affect garage conversions:

Parking replacement is no longer required when a garage is converted to an ADU within one-half mile of public transit, or when the garage is attached to the primary dwelling. This affects most conversions in urbanized parts of San Diego County.

Minimum lot sizes for ADUs cannot be enforced by local jurisdictions; state law overrides them.

Owner-occupancy requirements were suspended through 2025 and have been extended. Check current state law at hcd.ca.gov for the current status.

Impact fees for ADUs under 750 square feet are prohibited under state law. For larger units, fees must be proportional to the primary dwelling’s fees.

The permit process in the City of San Diego

The City of San Diego processes ADU permits through its Development Services Department. Since 2020, the city has worked to streamline the process with pre-approved ADU plans and an online submission portal. The typical timeline for a garage conversion ADU in the City of San Diego runs 4-8 months from application to permit issuance for standard projects, though timelines shift with department workload.

Steps in sequence:

Pre-application research. Confirm your lot’s zoning, setbacks, and any specific restrictions. The city’s Zoning Map and the development services portal at sandiego.gov/development-services are the starting points. Your contractor should do this before any plans are drawn.

Plan preparation. Your contractor or a draftsperson prepares architectural plans showing the proposed conversion: floor plan, electrical, plumbing, and energy compliance (Title 24). For a garage ADU, you will need a T24 energy compliance report showing insulation, windows, and mechanical systems meet current California Energy Code.

Plan check submittal. Plans go into the city’s online portal or over the counter. A first-round plan check typically takes 4-8 weeks. The city may come back with corrections, which require a revised submittal.

Permit issuance and construction. Once plans are approved and fees paid, the permit is issued. Construction begins. Inspections are required at specific milestones: framing, rough plumbing, rough electrical, insulation, and final.

Certificate of Occupancy. After the final inspection passes, the city issues a Certificate of Occupancy (or Occupancy Certificate for ADUs). This is the document that makes the unit legal to rent.

Other cities in San Diego County follow similar processes but have their own fee schedules and timelines. Chula Vista, Santee, and El Cajon have each updated their ADU ordinances to align with state law, but the specifics differ. Work with a contractor who knows your specific jurisdiction.

What the build process looks like

A garage-to-ADU conversion has a predictable sequence once permits are in hand.

Demo and prep. The garage door is removed and the opening is framed in with insulated walls, a door, and windows. Concrete is cut for plumbing rough-in if the bathroom and kitchen are not located along an exterior wall with easy access.

Rough framing and subfloor. If the garage slab is at grade (lower than the exterior finished floor), a sleeper system or raised subfloor is built to bring the interior floor up to code height and provide insulation from the cold slab. Interior partition walls are framed.

Mechanical rough-in. Plumbing, electrical, and HVAC are roughed in before walls are closed. The city inspector visits to confirm rough work meets code before drywall goes up.

Insulation and drywall. Exterior walls are insulated to Title 24 requirements. Drywall is hung and finished.

Finishes. Flooring, cabinetry, tile, paint, fixtures, and appliances go in. Electrical devices and covers are installed.

Final inspection. City inspector confirms everything matches the approved plans. A Certificate of Occupancy is issued.

Total construction time for a garage ADU ranges from 3-6 months depending on contractor availability, permit timeline, and the complexity of the plumbing and electrical work.

What to look for in a contractor

ADU conversions in California require a contractor with an active license from the Contractors State License Board (cslb.ca.gov). For a project that includes plumbing and electrical, you want a general contractor (B license) who coordinates trade subcontractors, or one who holds the specialty licenses themselves.

Verify any contractor’s license at cslb.ca.gov before signing a contract. Check that the license is active, that the contractor carries general liability insurance (ask for a certificate naming you as additional insured), and that they have workers’ compensation coverage.

For a referral to insured local crews who handle garage-to-ADU conversions across San Diego County, visit the garage conversion service page or contact us at (858) 925-5546.

Does California require parking replacement when I convert my garage to an ADU?

State law generally prohibits local jurisdictions from requiring parking replacement when a garage is converted to an ADU that is within one-half mile of public transit, or when the garage is attached to the primary dwelling. Most conversions in urbanized San Diego County qualify. Confirm with your local building department.

Can I convert a detached garage to an ADU in San Diego?

Yes. Detached garages can be converted to ADUs on single-family lots throughout San Diego County. Setbacks, height limits, and specific design requirements vary by jurisdiction, but state law limits local restrictions significantly.

How long does it take to get an ADU permit in San Diego?

In the City of San Diego, a standard garage ADU permit typically takes 4-8 months from application to permit issuance. Other cities vary. Construction adds another 3-6 months. Plan for 9-18 months total from first contractor meeting to move-in.

Do I need to owner-occupy my home to build a garage ADU?

Owner-occupancy requirements for ADUs in California were suspended by state law and the suspension has been extended. Check the current status at hcd.ca.gov, as the law continues to evolve.

For a full breakdown of what a garage-to-ADU project involves, see our full ADU conversion service page.